What to upgrade on 4L60E for robustness?

[EnvoyMan]

Soon after I got my 05 Envoy XL Denali running after a painful DoD delete process and driving it back to my home 4.5 hours away (graduated and moved out of my college apartment) my transmission started slipping in 3rd gear, sometimes grabbing 4th gear. A little bit after that, I completely lost 3rd gear (almost completely felt like neutral, have to rev it past 5k to even feel like I'm getting any semblance of power). From some brief research, this seems very much like a mechanical failure, as I didn't get any shift solenoid codes or anything like it, but I did get a torque converter clutch circuit code among other transmission slipping codes:

The strangest thing is that when I tried driving the car just to see how it's doing the next day, 3rd gear seemed to grab again. I didn't dare go fast enough to require 4th. What's up with that?

Feel free to correct me if I'm wrong, but no matter what, the fix seems very invasive and given that my full time job is starting soon, I will not have the time or energy to do this job myself. I will take this to a local transmission shop for an inspection and to decide whether it's worth saving this thing, but if I were to go for a rebuild, I was wondering what you guys recommend to upgrade for increased durability. I'm not trying to blow a ton of money into parts (want to stay under ~$1000 total), but I want something that will be better than before especially in terms of 3-4 gear reliability. I'm not going to race this thing, but I may tow a lot, with loads up to 4500-5000lbs. Technically the transmission should have been able to handle this stock but we saw how this ended up for me.

These are the parts that seem to come up all the time, therefore I'm looking to see if I should include these. Feel free to let me know if I should redirect my funds to different parts:
Sonnax 77733-06KA input housing kit. Really uncomfortably pricey but it claims to help with 3-4 clutch pack failure.

Sonnax 74602-01K reaction shaft kit. Don't fully understand what this does but it seems to come up in every rebuild post.

BEAST sunshell. OEM sunshells are common failures, but it may not be an issue on 2005 onwards transmissions so please let me know if I don't really need to go for this. I've heard people mention a heat treated OEM sunshell but I can't find it.

Sonnax HP-4L60E-01 performance pack. Seems to replace a lot of wearable parts, but I was happy with how the car shifted (until the transmission blew up) so if it just affects shift feel I won't bother.

Am I missing anything, or should I get rid of anything? I also stumbled across this rebuild kit: https://cyclonetransmission.com/pro...s-zpak-1993-2004?_pos=12&_sid=86e03ee43&_ss=r
If this has all the necessary upgrades I will stick with this, and my wallet will be happy too.

 

[Reprise]

The first thing you likely need is a new ignition switch module. Those 5 codes together are almost always indicative of a loss of connection between it and the transmission via the 'pink' wire in the harness.

The second thing you need, if you plan to tow, is an external transmission cooler; the integrated one in the radiator just doesn't get the job done under load / heat. Neither does the radiator, concerning engine cooling under heat / load (too small), but that's another topic.

The weakest part of the 4L60E is the 3-4 clutch pack. But once it goes (due to burning up or glazing), it doesn't 'come back', like yours did, which is another indication that you need to look at the ignition switch first, as I mention above.

$1000 isn't going to address improving reliability unless you were to do all of the work yourself, and your post indicates that that's not going to be the case. When I had my 4L60 rebuilt back in 2015-2016 (I forget the exact year), it was over $2000 USD all-in, and I supplied fluid and a trans cooler. With inflation since then, I'd probably budget $3000 for a removal / rebuild / reinstall.

Yes, the later GM sunshells were improved over the earlier versions. JayArr has an ongoing 4L60 rebuild thread, and I remember he covers this (with part #s, IIRC). I think my Beast ran about $85 or so, and if the costs are similar between aftermarket or OEM, I'd probably just go with a Beast (or Sonnax); you know those are right, no guesswork. But if the one in your Denali is the improved GM version, you (IOW, the rebuilder) could examine it on removal and potentially reuse it.

If the ignition switch replacement fixes your immediate issues, you can potentially avoid rebuilding the trans for now, install the trans cooler, and get a solution for the PWM / TCC valve assembly in the valve body, which tends to wear. You can do this via a Sonnax kit (JayArr did this), or a TransGo kit (most of the rest of us used), which can be installed without removing the whole transmission from the truck. You do need to remove the valve body, but it can be a DIY project, if you can follow directions and have some aptitude and a few tools.

Besides JayArr's thread, there are others on this site describing the ignition switch replacement, the TransGo kit install, and the various trans coolers people here have installed in their trucks. So I won't go into detail on all of that, and make this a super long post.

Finally, there are certain things in the 4L60E that are really not addressable, due to design / engineering limitations. The thing that fails the most is the 3-4 clutch pack, almost always due to excessive heat. So you need to address that, especially if you're planning on towing 4-5000 lbs with regularity. If your trans is close to or above 200K miles, you're probably on borrowed time with it, anyway (e.g.; give some thought to a full rebuild, or a lower mile replacement from a junkyard, etc.)

If you do go with the full rebuild, go with heavy duty 3-4 clutch packs; they'll buy you a little margin, but not a ton. Same for the 2-4 band. Talk with your chosen rebuilder about what he'd do to address the shortcomings for towing. There are various sites that describe the weak links in more detail, and whether or not they can be fully addressed. The next thing I'd address is the forward sprag, and after that the forward roller clutch. Five-pinion front / rear planetaries are nice, but very expensive. Me and my builder agreed they would be a waste of money, for what I was doing with my trans. Outside of towing (which I don't do with my Envoy anymore), I'm really not abusive with the driveline.

The 4L60E is a very good medium-duty auto trans (I'd certainly pit it against anything of a similar vintage), and it can be made stronger, but it can't be fully bulletproofed. That said, you have people in Camaros and the like who put 700+ HP to them; prepared properly, they'll live.

As the saying goes... 'search is your friend'. We have a lot of stuff on this site, and there are good resources outside of the site that will get you up to speed on the 4L60E, how to extend its life, and what can't be addressed (and 'why'). But it's a lot of reading.

If you want to get into the real nuts / bolts of the thing, ATSG has a rebuild manual, which we have links to, and is available for download (free) at other places, too. It's not a training guide (so it assumes you know a little about how transmissions work), but it does go over rebuilding the thing, step by step. It's a good read, especially if you're going to have it rebuilt, so you'll know what your rebuilder is talking about when he chats with you about the thing.

 

[TollKeeper]

Parkdale? as in Parkdale Colorado?

There are quite a few reputable tranny shops that can build it to your spec, for not much more money.

I will work on quite a few things, but transmissions are a wizardry above me.

 

[EnvoyMan]

Parkdale? as in Parkdale Colorado?

There are quite a few reputable tranny shops that can build it to your spec, for not much more money.

I will work on quite a few things, but transmissions are a wizardry above me.

I'm in Missouri, I have no idea why the site says I live in Colorado. Know of good shops there?

 

[EnvoyMan]

The first thing you likely need is a new ignition switch module. Those 5 codes together are almost always indicative of a loss of connection between it and the transmission via the 'pink' wire in the harness.

You really think it could be my ignition switch? I actually just replaced it to throw a part at a no crank/start issue I had that I just fixed a few days ago. My issue seemed to get progressively worse where it was just slipping at first during 2-3 shifts then complete loss at 3rd where it revved past 5k really fast and it barely had power at that RPM.

The second thing you need, if you plan to tow, is an external transmission cooler; the integrated one in the radiator just doesn't get the job done under load / heat. Neither does the radiator, concerning engine cooling under heat / load (too small), but that's another topic.

I may have put more importance into towing than I intended to. I mentioned it as an indicator of probably the toughest thing I would do with it. This wouldn't happen often, only if I were moving with my daily sedan for my job (will happen at least 3 times in the next year), and for short distance drives with my much lighter project car to the tuner shop.

The weakest part of the 4L60E is the 3-4 clutch pack. But once it goes (due to burning up or glazing), it doesn't 'come back', like yours did, which is another indication that you need to look at the ignition switch first, as I mention above.

That's what I heard the weakest link is, which is why I am interested in getting the Sonnax input housing kit that can fit more clutches even though it is an eye watering price. I was also looking into getting the Sonnax HD 3-4 clutch backing plate, but I don't know how necessary that is. I am pretty confused as to why 3rd came back. I'm returning my tow dolly today so it'll get some highway time, we'll see how it behaves. I will admit, I boogered up the connector for the ignition switch as it wouldn't budge with the tab pushed down, so eventually after enough forcing the tab just broke off. The connector still seemed to go in pretty snug so I wasn't super concerned. I have heard of these switches being bad from the factory too, but my bad luck would make sense given how awful it has been with this car. Do you know what the pink wire provides power for/through?

$1000 isn't going to address improving reliability unless you were to do all of the work yourself, and your post indicates that that's not going to be the case.

I meant $1000 in parts, if the trans shop let me supply parts. I'd be crazy to think I could get a rebuild and a R&R for that much.

But if the one in your Denali is the improved GM version

Any idea where I can find what year they put the improved shell in? I was leaning on the Beast shell if I do replace since it's way cheaper than the Sonnax one.

Finally, there are certain things in the 4L60E that are really not addressable, due to design / engineering limitations. The thing that fails the most is the 3-4 clutch pack, almost always due to excessive heat.

Since the 3-4 clutch failure seems to be the first big issue people get, I'm mainly looking to beef up that part of the transmission, because I still had 1, 2, and reverse, and also because...

If your trans is close to or above 200K miles

try 299k miles haha. The previous owner alleged that the transmission was already rebuilt by the previous previous owner, but he didn't have any documentation proving any such thing so I didn't believe it, and I especially don't after what I went through.

 

[TollKeeper]

I'm in Missouri, I have no idea why the site says I live in Colorado. Know of good shops there?

I do actually, but its not a close drive.. Over in St Peters. I used to live there.

They are 2 transmission shops, at the same location, or at least with the same address. Not sure how that works, but they did me good on my 727 Torque Flight in my Jeep..

Mr. Shift's Transmission Shop | Auto Repair | St. Peters, MO

Transmission repair shop. Transmission repair, rebuilding, and maintenance. Differential service. Clutch service. Call to schedule a free diagnostic.

www.mrshiftstransmission.com

They are also Mid-America Transmission and Auto (I think)

On my tranny, it initially turned out to not be anything in the transmission, but a TPS on the throttle. They were able to fix that for cheap. Then found a bad flare in the shift for 3-4. Replaced the valve body, and it was good. Original tranny at 280k, they could have easily said it was the tranny, and I would have believed it because of the miles.

Only caveat I will add, this was 20 years ago. I have no idea if they are the same shop or not.

 

[EnvoyMan]

I do actually, but its not a close drive.. Over in St Peters. I used to live there.

They are 2 transmission shops, at the same location, or at least with the same address. Not sure how that works, but they did me good on my 727 Torque Flight in my Jeep..

Mr. Shift's Transmission Shop | Auto Repair | St. Peters, MO

Transmission repair shop. Transmission repair, rebuilding, and maintenance. Differential service. Clutch service. Call to schedule a free diagnostic.

www.mrshiftstransmission.com

They are also Mid-America Transmission and Auto (I think)

On my tranny, it initially turned out to not be anything in the transmission, but a TPS on the throttle. They were able to fix that for cheap. Then found a bad flare in the shift for 3-4. Replaced the valve body, and it was good. Original tranny at 280k, they could have easily said it was the tranny, and I would have believed it because of the miles.

Only caveat I will add, this was 20 years ago. I have no idea if they are the same shop or not.

No way! I was looking at Mr. Shift's Transmission shop too. According to a review they used to go by a different name but it has the same owner. They seem super reputable, nice to find someone personally who can attest to their quality.

Edit: fixed an error

 

[JayArr]

Hi Envoyman

I just finished rebuilding my tranny myself and learned a lot with the help of this board.

My first piece of advice is: Decide if you really need to 'beef up' anything. The answer is probably no.

This transmission works great rebuilt as stock. Think about it, it's lasted 20 years and 200k since it left the factory. What are you hoping for that it will last 30 years and 300k? The rest of the car won't last that long. Once I realized this I stopped looking at performance parts or upgrade kits and my budget got a big sigh of relief. A stock rebuilt 4L60E is probably all you really need so forget the Sonnax input housing kit and the reaction shaft kit.

The sunshell in your transmission is probably already heat treated and there is really no need to replace a good part with a better part unless you like spending money for nothing. GM started heat treating their sunshells when the realized there was a problem and by 2005 the problem was all but fixed. Inspect it and if it's not damaged reuse it. I did.

Forget "shift kits", "performance packs", "corvette servos" and HD clutch packs it's an Envoy daily driver not a race car. Rebuilt as stock it will easily tow a 5000 pound trailer up the side of a mountain without any problem at all.

Make sure you tell the rebuilder that you want all of the bushings replaced. The basic rebuild kits only come with the "common wearing" bushings so an extra subkit is required to get all 11.

The PWM valve in the valvebody is a high wearing point, the piston is a harder aluminum than the casting so the casting wears out. When it does it bleeds pressure that was supposed to go to the 3/4 clutchpack, this causes the 3/4 clutch to not fully engage and it slips and burns. There are a number of ways to repair this, I chose the more expensive Sonnax way but may others use a less expensive Transgo kit with good results. There are a couple of threads on this here that you should read and then decide. If your rebuilder already has the reaming tool then the Sonnax is the same price, it's the tool that makes it more expensive the first time.

My rebuilt gets swapped in this weekend.

JayArr

 

[EnvoyMan]

Hi Envoyman

I just finished rebuilding my tranny myself and learned a lot with the help of this board.

My first piece of advice is: Decide if you really need to 'beef up' anything. The answer is probably no.

This transmission works great rebuilt as stock. Think about it, it's lasted 20 years and 200k since it left the factory. What are you hoping for that it will last 30 years and 300k? The rest of the car won't last that long. Once I realized this I stopped looking at performance parts or upgrade kits and my budget got a big sigh of relief. A stock rebuilt 4L60E is probably all you really need so forget the Sonnax input housing kit and the reaction shaft kit.

The sunshell in your transmission is probably already heat treated and there is really no need to replace a good part with a better part unless you like spending money for nothing. GM started heat treating their sunshells when the realized there was a problem and by 2005 the problem was all but fixed. Inspect it and if it's not damaged reuse it. I did.

Forget "shift kits", "performance packs", "corvette servos" and HD clutch packs it's an Envoy daily driver not a race car. Rebuilt as stock it will easily tow a 5000 pound trailer up the side of a mountain without any problem at all.

Make sure you tell the rebuilder that you want all of the bushings replaced. The basic rebuild kits only come with the "common wearing" bushings so an extra subkit is required to get all 11.

The PWM valve in the valvebody is a high wearing point, the piston is a harder aluminum than the casting so the casting wears out. When it does it bleeds pressure that was supposed to go to the 3/4 clutchpack, this causes the 3/4 clutch to not fully engage and it slips and burns. There are a number of ways to repair this, I chose the more expensive Sonnax way but may others use a less expensive Transgo kit with good results. There are a couple of threads on this here that you should read and then decide. If your rebuilder already has the reaming tool then the Sonnax is the same price, it's the tool that makes it more expensive the first time.

My rebuilt gets swapped in this weekend.

JayArr

Hi JayArr! Thanks for commenting on this post. Reading your first few paragraphs made me realize that yes, I don't need to beef up my transmission since it already lasted this long. I am at almost 300k, so I would be more than happy if I at least got 100k more miles out of it, provided nothing else fails (although I'm sure something will). That extra mileage is almost double the mileage I've put on my trusty Toyota Camry, which is my first car from over 3 years ago and still is my daily. How much did you end up spending on parts, tools, and most importantly, time? Looking at your post it seems that you pretty much did everything on your own.

I want to believe my sunshell is fine, as apparently you lose 2nd, 4th, and reverse gear when it breaks. If I rebuilt it myself, I would at least get the heavier duty 3/4 clutch packs as I feel that would be worth it for longevity. The rebuilder I am leaning on however has such a long lead time for their rebuilds, they are currently recommending remans where they make improvements to support the 3/4 clutch packs, such as replacing the input drum, pressure regulators, TCC regulator valves, the boost valve, and a number of other regulators and valves. They are offering the transmission, and the R&R for $1900 which seems very reasonable to me.

Your bit about the PWM valve is interesting. Do you know if there's a way to check if it's bleeding pressure without disassembling the transmission? I wonder if I'm having that issue, as I can get the car to still accelerate in 3rd gear from a stop at a reasonable speed, but then as soon as I go faster it just slips and slips but if you rev it hard enough, it will start to SLOWLY gain speed again but at that point I'm pushing 5500+ RPM at 45mph. Can this repair kit install be done without removing the transmission or is removal required? The rebuilder mentioned something about reaming so I believe they have the tool. Let me know your thoughts on my questions. Best of luck with your rebuild install, hope everything goes well.

 

[JayArr]

Hi EM

Explain to us what the "Heavier Duty" clutch packs are. Do you know how or why they are HD? The thing is that there is only so much space for the 3/4 clutch pack. If the frictions are thicker then you can't put as many in, I think 7 is normal so you need to ask yourself if 6 thicker friction discs are better than 7 regular ones? The other way is to make the steels thinner and put in 7 thicker friction discs but then the steels are more susceptible to warping under heat. This 'heavy duty' clutch pack you're looking at might just be snake oil.

How much did I spend? I'm almost afraid to add it all up. It would be close to the $1900 you were quoted for an R&R. Which doesn't sound like a bad deal if the shop is reputable and the quality decent.

I bought all the tools, I mean all of them. I intend to rebuild a half dozen or more of these in the next few years and I may rebuild them as a side hustle in retirement so the tools will pay off. For parts I probably only spent $800-$900USD but if I had shopped around I could have gotten that down to $600.

The PWM can be repaired without pulling the transmission. You need to drain and drop the pan and then you can remove the valve body from the transmission from under the car. Take it back to the bench, ream it out (takes 10 minutes) insert a Sonnax sleeve and new valve and bolt it all back together. This should be doable by a decent shadetree mechanic in an afternoon.

Here's an idea. ask your rebuilder if you can get a rebuilt valve body from him. One that he has already reamed and sleeved. Then do the swap one Saturday afternoon and return your old valve body to him to rebuild for the next guy. If the price is right it would save you having to buy the tools. If he won't go for it look at Sonnax, they sell them all reconditioned and ready to go. If you lived closer I'd tell you to drop by, reaming it out was amazingly easy.

JayArr

BTW, here's a set of youtube videos I watched to get the idea of how to do this rebuild. His aname is Brad and he's really good. I think I've watched it a dozen times.

 

[TJBaker57]

if I were moving with my daily sedan for my job (will happen at least 3 times in the next year),

With this in mind fully investigate any warranty for a reman transmission. I got burned once while travelling. My Yukon 4l60E went out and needed rebuild. Chose a shop with a good reputation and had a standard full rebuild. About $2500. A few months later and over a thousand miles away the rebuild fails. I was close to an AAMCO shop I had personal experience with on a different 4L60E rebuild. They were also a member of the same rebuilders association the other shop was but more or less said that associations warranty was worthless paper. Another $2400 later I was good to go.

 

[EnvoyMan]

With this in mind fully investigate any warranty for a reman transmission. I got burned once while travelling. My Yukon 4l60E went out and needed rebuild. Chose a shop with a good reputation and had a standard full rebuild. About $2500. A few months later and over a thousand miles away the rebuild fails. I was close to an AAMCO shop I had personal experience with on a different 4L60E rebuild. They were also a member of the same rebuilders association the other shop was but more or less said that associations warranty was worthless paper. Another $2400 later I was good to go.

Good point, I actually did ask for it when I initially called the shop, and they mentioned their cheaper reman warranty is only obligated to be honored by them, but their more expensive option (which I don't want to go for) is $3100 and I can take it to any ATRA certified shop. That really sucks what happened to you.

 

[EnvoyMan]

Hi EM

Explain to us what the "Heavier Duty" clutch packs are. Do you know how or why they are HD? The thing is that there is only so much space for the 3/4 clutch pack. If the frictions are thicker then you can't put as many in, I think 7 is normal so you need to ask yourself if 6 thicker friction discs are better than 7 regular ones? The other way is to make the steels thinner and put in 7 thicker friction discs but then the steels are more susceptible to warping under heat. This 'heavy duty' clutch pack you're looking at might just be snake oil.

How much did I spend? I'm almost afraid to add it all up. It would be close to the $1900 you were quoted for an R&R. Which doesn't sound like a bad deal if the shop is reputable and the quality decent.

I bought all the tools, I mean all of them. I intend to rebuild a half dozen or more of these in the next few years and I may rebuild them as a side hustle in retirement so the tools will pay off. For parts I probably only spent $800-$900USD but if I had shopped around I could have gotten that down to $600.

The PWM can be repaired without pulling the transmission. You need to drain and drop the pan and then you can remove the valve body from the transmission from under the car. Take it back to the bench, ream it out (takes 10 minutes) insert a Sonnax sleeve and new valve and bolt it all back together. This should be doable by a decent shadetree mechanic in an afternoon.

Here's an idea. ask your rebuilder if you can get a rebuilt valve body from him. One that he has already reamed and sleeved. Then do the swap one Saturday afternoon and return your old valve body to him to rebuild for the next guy. If the price is right it would save you having to buy the tools. If he won't go for it look at Sonnax, they sell them all reconditioned and ready to go. If you lived closer I'd tell you to drop by, reaming it out was amazingly easy.

JayArr

BTW, here's a set of youtube videos I watched to get the idea of how to do this rebuild. His aname is Brad and he's really good. I think I've watched it a dozen times.

If I were able to get a rebuild, I would have gone for the Raybestos cluch pack that is really highly regarded. $1900 to do it yourself is certainly a lot, so I may find it worth just getting a shop to do it so I can spare myself the inevitable headaches I will run into. I might give the PWM valve replaced a shot if the shop figures out the problem isn't in my clutch packs but in my electronics. The thing that concerns me is that I didn't get any codes for that, as I posted earlier I got a code for the a transmission component slipping, as well as the "TCC circuit performance or stuck off" code, which I really don't know how to investigate.

 

[TJBaker57]

but their more expensive option (which I don't want to go for) is $3100 and I can take it to any ATRA certified shop.

Wellll, both shops involved in my debacle were ATRA certified shops. Just sayin...

 

[TJBaker57]

the "TCC circuit performance or stuck off" code, which I really don't know how to investigate.

I 'think' this code is one that gets set when the TCC PWM is failing as described.

My TrailBlazer first started exhibiting the TCC PWM failure at 205000 miles. I would notice the TCC break free occasionally while cruising at about 60 - 65 mph. The engine rpm would come up maybe 200 rpm with no change in speed or road conditions. I would immediately decrease the throttle a bit and it would catch again. With the Torque app I monitored the data parameters for TCC slip as well as some others and always let off the throttle a bit and let it re-engage. I got another 20000 miles before the trans was really a goner and had it rebuilt. The rear planetaries got wiped out due to a lack of fluid pressure to lubricate there. No issues with that trans since the AAMCO rebuild some 70000 miles ago.

 

[EnvoyMan]

I 'think' this code is one that gets set when the TCC PWM is failing as described.

My TrailBlazer first started exhibiting the TCC PWM failure at 205000 miles. I would notice the TCC break free occasionally while cruising at about 60 - 65 mph. The engine rpm would come up maybe 200 rpm with no change in speed or road conditions. I would immediately decrease the throttle a bit and it would catch again. With the Torque app I monitored the data parameters for TCC slip as well as some others and always let off the throttle a bit and let it re-engage. I got another 20000 miles before the trans was really a goner and had it rebuilt. The rear planetaries got wiped out due to a lack of fluid pressure to lubricate there. No issues with that trans since the AAMCO rebuild some 70000 miles ago.

You went with AAMCO the second time? Was that $2400?

 

[TJBaker57]

You went with AAMCO the second time? Was that $2400?

I chose the particular shop based on many positive reviews of that particular shop, not so much because it was an AAMCO shop.

I used that AAMCO shop first for my TrailBlazer. When they test drove it they concluded best would be a full rebuild and quoted a price. I asked "what if you find something unexpected in there, would there be additional cost?" He said no, the quote is firm and they do 4L60E all the time. Sure enough when he got into it they discovered the blown out rear planetary and some other component that usually is not part of the standard rebuild. The added parts were another $400 or so but since they assured me the quoted price would hold they made no additional charges and held to their quote.

So when the Yukon trans went out shortly after another shops rebuild I went right back to the AAMCO shop that did the TrailBlazer. I was lucky that I was in that town and the Yukon remained mobile at the time. The most they would tell me about the other shops failed rebuild was that they had to "work on the valve body".

The $2400 is an approximate after tax amount.

 

[6716]

With some help from a buddy of mine, I pulled the transmission and handed it to a rebuilder who worked at a transmission shop but did side work out of his garage. It has held up to towing so far and seems ok after 25k miles.

I also replaced the catalytic converter section since that comes out anyway to get get the transmission down, and did O2 sensors.

After I crushed a sleeve on the torque converter putting it in the first time and had to get that re-rebuilt, and with wait time and all that, and extra tools, I am pretty certain I would have spent less and had it back on the road sooner if I had just brought it to a decent shop.

Fortunately I had access to another vehicle in the repair process.

Anyway, here's a thread https://gmtnation.com/forums/threads/pulling-the-transmission-this-weekend.17614/

 

[gmcman]

@EnvoyMan Sorry I didn't see this earlier.

Not to kick a dead horse, or start off on a bad note, but if you get slippage in the trans, running the RPM's up to get somewhere will just smoke the clutches fast. Anytime it slips, let off and see when and where it slips then maybe even pull over..if possible of course.

You can always select 2nd gear and the trans will start in 2nd and not downshift unless you really stomp on it...you can use 2nd to limp somewhere if it's within a reasonable distance and 2nd still holds.

A weak area is the seperator plate, I had a check ball punch through and I had a pressure loss after the 2-3 shift.

What I would do for a rebuild is the vette servo, sonnax super hold servo, aluminum accumulator pistons, PWM eliminator kit, along with what you have mentioned.

The 4L60E has a bunch of bushings that need to be installed correctly, as well as the pump housing put together in a very precise manner with a special band clamp.

I used Pro Build Automatics in California to get my servos and PWM kit, Dana the owner knows these things backwards and forwards.

If that were my Envoy, I would likely consider the trans toast at this point but you could pull the valve body and inspect the seperator plate if you want to confirm. But maybe you can check it out and keep driving it, but the 3rd clutch pack may be compromised for towing...who knows.

Mine had the bad 2-3 shifting flare around 165K miles. I replaced the plate, accumulator pistons, added the vette servo and it was still working good at 340K miles when my newest driver "connected" with the person stopped in front. I may still repair the nose and keep driving it but that's another story.

I was ready to drop the valve body and install a new plate as preventative maintenance...but not at the moment.

Hope this helps you.

 

[RiverGuy]

Soon after I got my 05 Envoy XL Denali running after a painful DoD delete process and driving it back to my home 4.5 hours away (graduated and moved out of my college apartment) my transmission started slipping in 3rd gear, sometimes grabbing 4th gear. A little bit after that, I completely lost 3rd gear (almost completely felt like neutral, have to rev it past 5k to even feel like I'm getting any semblance of power). From some brief research, this seems very much like a mechanical failure, as I didn't get any shift solenoid codes or anything like it, but I did get a torque converter clutch circuit code among other transmission slipping codes:
View attachment 108953
The strangest thing is that when I tried driving the car just to see how it's doing the next day, 3rd gear seemed to grab again. I didn't dare go fast enough to require 4th. What's up with that?

Feel free to correct me if I'm wrong, but no matter what, the fix seems very invasive and given that my full time job is starting soon, I will not have the time or energy to do this job myself. I will take this to a local transmission shop for an inspection and to decide whether it's worth saving this thing, but if I were to go for a rebuild, I was wondering what you guys recommend to upgrade for increased durability. I'm not trying to blow a ton of money into parts (want to stay under ~$1000 total), but I want something that will be better than before especially in terms of 3-4 gear reliability. I'm not going to race this thing, but I may tow a lot, with loads up to 4500-5000lbs. Technically the transmission should have been able to handle this stock but we saw how this ended up for me.

These are the parts that seem to come up all the time, therefore I'm looking to see if I should include these. Feel free to let me know if I should redirect my funds to different parts:
Sonnax 77733-06KA input housing kit. Really uncomfortably pricey but it claims to help with 3-4 clutch pack failure.

Sonnax 74602-01K reaction shaft kit. Don't fully understand what this does but it seems to come up in every rebuild post.

BEAST sunshell. OEM sunshells are common failures, but it may not be an issue on 2005 onwards transmissions so please let me know if I don't really need to go for this. I've heard people mention a heat treated OEM sunshell but I can't find it.

Sonnax HP-4L60E-01 performance pack. Seems to replace a lot of wearable parts, but I was happy with how the car shifted (until the transmission blew up) so if it just affects shift feel I won't bother.

Am I missing anything, or should I get rid of anything? I also stumbled across this rebuild kit: https://cyclonetransmission.com/pro...s-zpak-1993-2004?_pos=12&_sid=86e03ee43&_ss=r
If this has all the necessary upgrades I will stick with this, and my wallet will be happy too.

I had a soft shift (2-3 if I recall correctly) in my 2003 Bravada at about 130k and it cleaned up completely by swapping in the 'Corvette Servo' that was recommended somewhere. I absolutely loved the feel and drove it for about 10,000 miles that way. Only sold it when I found my current Final 500 Olds and didn't need it anymore. At the time, the tranny shop guy said this was the easiest/cheapest mod to make a 4L60E last longer. I had been thinking about a full-blown shift kit like I did with my 1970 Olds 442, but the new servo did the trick. I think I got the servo on Amazon for $40. I would do the servo and other hydraulic-only mods before tearing it down, especially if you don't have any evidence of worn or burned clutch plates. What color is your tranny fluid, what does it smell like and what did you find on the pan magnet(s)?