4L60E TCC questions

[Mr. Peabody]

Hi Everybody,

I am new to this site and have a few questions about my 4L60E transmission.

A while back I purchased a 2008 Envoy with 160,000 miles on it to be my tow vehicle for my 3000 lb boat. I'm very pleased with the towing ability of my Envoy and to me everything seems to be in good working order, but as I learn more about the vehicle I have some questions.

I purchased a Bluetooth OBD2 reader and the Torque Pro app to monitor what's going on in the tranny. Through the app I have noticed that I always have a lot of TCC slip.

Even when not towing, at 60 mph on the expressway I see TCC slip of 200 rpm, and more when I accelerate.

When I'm towing I routinely see 200 to 300 rpm of slip while cruising and 500 to 600 rpm of slip when gong up a hill.

When I'm not towing I sometimes see TCC slip numbers of 1 to 10 RPM, but that is rare and I have to be driving on a flat road with no headwinds.

Is this normal for the 4L60E, or is there a problem with my transmission ?

Also, in case you are wondering about heat, I was hitting 220 degrees while towing so I added a transmission cooler and now the temp stays below 180, even while towing.

 

[TJBaker57]

Hi Everybody,

I am new to this site and have a few questions about my 4L60E transmission.

A while back I purchased a 2008 Envoy with 160,000 miles on it to be my tow vehicle for my 3000 lb boat. I'm very pleased with the towing ability of my Envoy and to me everything seems to be in good working order, but as I learn more about the vehicle I have some questions.

I purchased a Bluetooth OBD2 reader and the Torque Pro app to monitor what's going on in the tranny. Through the app I have noticed that I always have a lot of TCC slip.

Even when not towing, at 60 mph on the expressway I see TCC slip of 200 rpm, and more when I accelerate.

When I'm towing I routinely see 200 to 300 rpm of slip while cruising and 500 to 600 rpm of slip when gong up a hill.

When I'm not towing I sometimes see TCC slip numbers of 1 to 10 RPM, but that is rare and I have to be driving on a flat road with no headwinds.

Is this normal for the 4L60E, or is there a problem with my transmission ?

Also, in case you are wondering about heat, I was hitting 220 degrees while towing so I added a transmission cooler and now the temp stays below 180, even while towing.

Granted, I do not know a lot about transmissions but my guess is you have a transmission problem and I suspect the TCC pressure circuit. There is a known fault that happens there.

FWIW my slip is nearly always within one or two rpm of zero when cruising.

20 Years Later: What’s New with 4L60-E PWM Modifications

Transmission builders are no strangers to modification. Making changes to increase performance, to prevent known issues from cropping up or to overcome existing

www.sonnax.com

 

[Mr. Peabody]

FWIW my slip is nearly always within one or two rpm of zero when cruising.

Hmm, sounds like I've got some problems brewing.

Thanks for your reply.

 

[Mooseman]

Easiest and cheapest way to fix it is to eliminate the PWM for the TCC. It will just lock up when commanded. Eliminates a lot of heat too.

 

[Mr. Peabody]

Easiest and cheapest way to fix it is to eliminate the PWM for the TCC. It will just lock up when commanded. Eliminates a lot of heat too.

I'm very interested in this option. If I understand correctly I might be able to do this by dropping the valve body and not removing the tranny, is that correct ?

Could you recommend a kit or instruction sheet on how to eliminate the PWM ?

Thanks so much !!

 

[JayArr]

Take a look at the Transgo kit, I think you may be able to install it without even dropping the valve body (just the pan)

 

[Mr. Peabody]

Take a look at the Transgo kit, I think you may be able to install it without even dropping the valve body (just the pan)

Thanks, I'll do that.

I really appreciate everyone's help !!

 

[Mr. Peabody]

I've been searching the interwebs and found this. It looks simple to do.

Do the experts here think this is legitimate ?

 

[gmcman]

@Mr. Peabody Before you go tearing into your transmission, I wanted to add some to this discussion.

When you have the factory setup, with the PWM TCC, when you get up to speed, I believe somewhere around 45-55 MPH, the converter will lock almost inperceivably, that's the function of the PWM control.

One way to confirm this is while holding a steady pressure on the gas pedal, do not lift off, use your left foot and tap the brakes. You should see the RPM's rise about 200 RPM's then they will settle back down. Also, if the converter is locked and you lift off the gas pedal, it will unlock until you apply steady pressure to the gas pedal and it's not under a heavy load.

The trans temp needs to be above a certain temp for the lock to happen, also I don't think I have ever seem my TCC slip RPM reach zero while viewing the Torque diaplay...and that was before and after I did the PWM eliminator mod. Usually it's always between 1 and 10 ish RPM.

The PWM eliminator kit is easy to do. What you want keep an eye on at all times, is the 2-3 shift. If you start to see the RPM's rise about 2-300 RPM during the shift under load, that could be a sign of a pressure loss somewhere. With mine it happened around 165K miles and I had a check ball pound it's way through the seperator plate but caught it early. This is a weak link in these transmissions and I would recommend replacing around that mileage with a factory OE plate.

This is my personal preference, but I'm not a fan of cranking up pressures in the trans. I opted for the TCC eliminator, vette servo, and I would recommend the Sonnax 4th apply piston, the "Super Hold" piston in conjunction with the vette servo, they go in the same location.

There is also a mod where you can drill a larger hole in the plate for added TCC pressure and that's what I did...no boost valve or other mods. I wanted stock pressure and more holding power.

HTH.

 

[Mooseman]

You could also tune it to apply 100% TCC whenever it's called for. That's what I did and it feels like a 5th gear. There is apparently another mod to the solenoid

I've been searching the interwebs and found this. It looks simple to do.

Do the experts here think this is legitimate ?

I've seen this video before and comments seem to suggest this works. Try it and if it fails, you can always get a new solenoid. I've never tried it as I went the tune route. That's another way you could eliminate the PWM. If the bore is leaky though, it might not work.

 

[Mr. Peabody]

@Mr. Peabody Before you go tearing into your transmission, I wanted to add some to this discussion.

When you have the factory setup, with the PWM TCC, when you get up to speed, I believe somewhere around 45-55 MPH, the converter will lock almost inperceivably, that's the function of the PWM control.

One way to confirm this is while holding a steady pressure on the gas pedal, do not lift off, use your left foot and tap the brakes. You should see the RPM's rise about 200 RPM's then they will settle back down. Also, if the converter is locked and you lift off the gas pedal, it will unlock until you apply steady pressure to the gas pedal and it's not under a heavy load.

The trans temp needs to be above a certain temp for the lock to happen, also I don't think I have ever seem my TCC slip RPM reach zero while viewing the Torque diaplay...and that was before and after I did the PWM eliminator mod. Usually it's always between 1 and 10 ish RPM.

The PWM eliminator kit is easy to do. What you want keep an eye on at all times, is the 2-3 shift. If you start to see the RPM's rise about 2-300 RPM during the shift under load, that could be a sign of a pressure loss somewhere. With mine it happened around 165K miles and I had a check ball pound it's way through the seperator plate but caught it early. This is a weak link in these transmissions and I would recommend replacing around that mileage with a factory OE plate.

This is my personal preference, but I'm not a fan of cranking up pressures in the trans. I opted for the TCC eliminator, vette servo, and I would recommend the Sonnax 4th apply piston, the "Super Hold" piston in conjunction with the vette servo, they go in the same location.

There is also a mod where you can drill a larger hole in the plate for added TCC pressure and that's what I did...no boost valve or other mods. I wanted stock pressure and more holding power.

HTH.

GMCMan,

Thanks for all the added info !!

Your post got me thinking, and I may well have put the cart before the horse. I haven't had a chance to do the tests you outlined, but the ONLY reason I suspect that I might have a transmission problem is because of the Torque app showing a lot of slip. I have never noticed anything unusual about the tranny before I got the Torque app.

It is certainly possible that the Torque app is off, I have several other PID displays that are obviously wrong.

I was driving around a few days ago and I think I was going about 50 mph on flat ground. The Torque app showed between 200 and 300 rpm slip. I remember looking at the dashboard Tachometer and the engine speed was about 1,400 rpm. That doesn't seem out of the ordinary to me, and I have to wonder if it's really practical to go 50 at 1,100 rpm or so.

I'll do your tests and report back, but it is possible that I'm chasing my tail simply because of some numbers on a phone app.

 

[Mr. Peabody]

You could also tune it to apply 100% TCC whenever it's called for. That's what I did and it feels like a 5th gear. There is apparently another mod to the solenoid

I've seen this video before and comments seem to suggest this works. Try it and if it fails, you can always get a new solenoid. I've never tried it as I went the tune route. That's another way you could eliminate the PWM. If the bore is leaky though, it might not work.

Moosman,

Even though I posted above that I may not have a problem at all, I do have a question about your reply.

When you state "if the bore is leaky though, it might not work" were you referring to the solenoid mod, the tune, or maybe both ?

Thanks so much !!

 

[gmcman]

I was driving around a few days ago and I think I was going about 50 mph on flat ground. The Torque app showed between 200 and 300 rpm slip

How long have you been driving it after the cold start?

I don't know the threshold, but the trans needs to be up to a certain temp before the TCC will lock.

The 4L60E will lock in 3rd and 4th, you could try both gears.

Also, it won't lock unless you have your foot on the gas and are under a slight load. So to test this, I would get it to about 45-50 MPH with the gear selector in 3rd, or at 55-60 in 4th just to be safe.

Here's a screenshot of my HPTuners stock tune. The graph is kinda hard to understand, but I'm fairly certain the chart on the left shows the speeds the TCC will apply at certain throttle settings. Note that at 62% or more the TCC will disengage, also disengaged in 2nd full time. That's how GM sets the "no-go" zone by using speeds that aren't achievable in orange and red.

So in 3rd, mine won't lock until 27 MPH min, and 37 MPH min in 4th if other conditions are present like trans temp etc.



Another graph that's slightly above my pay grade, shows max duty cycle at 96% for the TCC. This could explain the 1-10 ish RPM slip speed. I know GM uses TCC's that are designed to slip and run very happily like that.

 

[mrrsm]

Mr. Peabody... This is WOT (WAY Off Topic)...but since I've learned an AWFUL lot of Good Science and developed much of my *Keen Intellect and a Sense of Humor* from watching you over the years... I thought you'd appreciate finding THESE Videos courtesy "The Internet Archive":

Mr Peabody And Sherman : Free Download, Borrow, and Streaming : Internet Archive

Mr Peabody And Sherman

archive.org

 

[Mr. Peabody]

Today I had a chance to do the tests Gmcman recommended. The trans temp was 145 f (that's pretty much as hot as it gets when not towing after I installed a trans cooler). It was 92 degrees F and I was cruising along flat roads at various speeds between 50 and 65. Tapping the brakes made no difference in engine speed.

I also paid more attention to the Torque app, and everything I see looks legit. When stopped at a light the TCC slip RPM is pretty much the same as the engine RPM. When cruising on flat roads I can "control" the TCC slip with the accelerator. For short times I can keep it around 10 to 40 rpm, but I tend to lose road speed. If I take my foot off the accelerator TCC slip goes negative. If I press the gas TCC slip goes into high numbers 500 rpm +

As I mentioned before, everything about my trans seems normal, and I didn't realize that there might be a problem until I got the Torque app. I owned the vehicle for 20K miles now and there have been no problems. I've got the trans temps under control with the additional trans cooler.

I wonder how long I can go like this w/o any problems ? I'm sure nobody knows.

I'm not sure what to do next, but thanks to everyone for your help up to this point.

 

[gmcman]

FWIW, I never saw my TCC slip at 0. I can't remember exactly what it was but the 10-40 RPM seems about right....can't say for sure.

When you did the brake test, were you cruising under a light load, which is more or less a steady cruise, with your foot on the gas, without moving the gas pedal?

 

[Mr. Peabody]

FWIW, I never saw my TCC slip at 0. I can't remember exactly what it was but the 10-40 RPM seems about right....can't say for sure.

When you did the brake test, were you cruising under a light load, which is more or less a steady cruise, with your foot on the gas, without moving the gas pedal?

Gmcman,

Yes, you are correct, I didn't mean to imply that I could cruise and 0 slip. What I meant to say was that I could pass from positive slip, to zero, to negative slip by letting off the gas. That was my bad.

Yes, when I did the brake test I did as you posted, light load, foot on the gas, did not move the gas pedal.

 

[gmcman]

Ok, copy that.

When I was testing mine, I watched the TCC slip along with engine RPM from the app.

You will see when the TCC locks so you don't try this with it unlocked.

Also, when you are cruising along at a steady speed, if you press on the gas a little harder for a sec or 2, do the RPM's kinda stay put, or rev up 2-300 RPM?

If they barely rise, you know the TCC is locked.

 

[Mr. Peabody]

OK, good idea to add the engine RPM to Torque, I'll do that tomorrow.

I'll be able to better report what happens if I press on the gas a little harder after changing Torque, but right now I'm inclined to say that the engine revs up 2-300 rpm.

Thank you so much for your interest and your help !!

 

[TJBaker57]

FWIW, I never saw my TCC slip at 0. I can't remember exactly what it was but the 10-40 RPM seems about right

Makes me wonder if my rebuilder altered something in mine without saying so. I almost always get damned near 0 at cruise. Was an AAMCO shop doing a standard rebuild.

I zoomed in on the Y axis in the second image to get finer detail.

 

[Mooseman]

They could have modified the TCC for 100% engagement since it is a problematic area. Do you feel it engage like a 5th gear? I'd be happy with that to avoid wear in the TCC valve bore and the TCC itself.

 

[Sparky]

They could have modified the TCC for 100% engagement since it is a problematic area. Do you feel it engage like a 5th gear? I'd be happy with that to avoid wear in the TCC valve bore and the TCC itself.

That's exactly what all my 4L60E transmissions (3 of them) have felt like after putting in the Transgo kit. I like that. Positive engagement (not rough at all), no slip, and best of all, no more problems (or risk of problems) with the TCC causing excessive heat and wear (and eventual failure) and better mpg (amazing how much extra gas that 200-300 extra RPM can suck up on the highway).

I've put over 240k miles combined across three transmissions - one had real bad issues before it - and they've been flawless.

I like the ctpowertrain combination kit that you can get off ebay. When you open the valve body, you'll probably need new seals, find your separator plate is worn, etc. The kit basically comes with everything you need. just get the correct year range as the plates are a little different.

 

[Mr. Peabody]

So I think I know what's going on with my transmission.

Up to this point I have always waited until the trans was up to temperature to monitor TCC slip. This morning I set up the Torque app and started monitoring during my first drive of the morning. Everything was "cold" (it was 80 degrees F this morning).

Much to my surprise everything was working perfectly. Once I got up to speed on relatively flat roadway the TCC slip dropped to 30-50 rpm !! I thought this was odd as I have never been able to achieve that much lockup since I started monitoring it.

I kept monitoring the situation and once the transmission fluid got to about 120 degrees F the ability to lock up went away. The hotter the ATF got, the more slip I measured.

My amateur theory is that the TCC valve body is worn. When the ATF is cool it is thick enough to allow some locking, but once the ATF gets hot it thins out and then bypasses the TCC valve due to the bore wear.

Does that sound logical ?

If so, I wonder if this is the solution I need:

https://www.fitzall.com/A74741CB.php

 

[Sparky]

So I think I know what's going on with my transmission.

Up to this point I have always waited until the trans was up to temperature to monitor TCC slip. This morning I set up the Torque app and started monitoring during my first drive of the morning. Everything was "cold" (it was 80 degrees F this morning).

Much to my surprise everything was working perfectly. Once I got up to speed on relatively flat roadway the TCC slip dropped to 30-50 rpm !! I thought this was odd as I have never been able to achieve that much lockup since I started monitoring it.

I kept monitoring the situation and once the transmission fluid got to about 120 degrees F the ability to lock up went away. The hotter the ATF got, the more slip I measured.

My amateur theory is that the TCC valve body is worn. When the ATF is cool it is thick enough to allow some locking, but once the ATF gets hot it thins out and then bypasses the TCC valve due to the bore wear.

Does that sound logical ?

If so, I wonder if this is the solution I need:

https://www.fitzall.com/A74741CB.php

Those are the exact same symptoms my first 4L60E had. Warmed up, TCC lock, then as it got warmer, the lockup would disappear. The hotter the weather, the faster I'd lose lockup.

That thing may work. I am not familiar with it. Not sure why it matters if CANbus or not. I used that transgo stuff and it didn't have anything to do with any electronics.

 

[Mooseman]

Maybe because Canbus is when PWM was introduced? Anyway it looks like it uses o-rings to fix the leaky valve.

 

[gmcman]

Does that sound logical ?

It does.

When I did mine I used the Transgo kit, worked perfect. Also drilled a hole on the new plate for added pressure.

I'll dig the link up.

Edit: found it.

https://gmtnation.com/forums/threads/removed-pwm-control-from-tcc.7238/

 

[Mr. Peabody]

Not sure why it matters if CANbus or not.

There web site states:

"The redesign of our A74741QA valve will not set code on vehicles with CAN Bus.
We accomplish this by allowing the valve to unlock the converter if the PWM drops
to a very low duty cycle, while still sealing the worn valve bore"

I don't really understand that, it's beyond me.

I'm trying to figure out if this changes TCC lock to ON/OFF or if it retains the PWM sorta locked, sorta not locked functionality. It can be installed w/o removing the valve body, so if I can determine that it's for real and works, I will give it a try.

This link shows an exploded view, and there is no spring used.

https://www.fitzall.com/cmsAdmin/uploads/3/a74741cb-instruction-sheet.pdf

 

[Mooseman]

I'd just use the TransGo kit. It's been around forever and it works.

 

[Sparky]

Maybe because Canbus is when PWM was introduced? Anyway it looks like it uses o-rings to fix the leaky valve.

Not really. My 1998 Camaro had PWM on the TCC (that's the one that started flaring and having all the issues). They reference 2007. My 2007 Silverado didn't do anything funky when I installed the Transgo kit in it.

I'd just use the TransGo kit. It's been around forever and it works.

I agree.

 

[Mr. Peabody]

My only problem with the TransGo kit is that I suspect it's beyond my abilities. I don't feel comfortable dropping the valve body.

I went to a transmission shop today and spoke with them about it. The guys recommendation was at its age and miles (183k) to drive it until it fails, then do a complete rebuild.

I suspect he wanted the most expensive option for his benefit 😁

 

[mrrsm]

This ATSG 4L60E-80 OBD2 Code Diagnostics Manual, the related Diagnostic Charts and the Transfer Case Component Specifications and Compatability PDFs may prove very useful to you:

 

[Sparky]

My only problem with the TransGo kit is that I suspect it's beyond my abilities. I don't feel comfortable dropping the valve body.

I went to a transmission shop today and spoke with them about it. The guys recommendation was at its age and miles (183k) to drive it until it fails, then do a complete rebuild.

I suspect he wanted the most expensive option for his benefit 😁

First time I did it, I thought it was over my ability too. Granted, I had some help of a buddy, but it really isn't THAT bad to do. Just have a good work space set up, and keep track of the parts and where they go.

 

[gmcman]

I agree, the first time I removed the valve body I had second thoughts, but it was just a bunch of bolts then it came down, was a piece of cake. The only tricky part was getting the shift lever plunger back in place lying on your back.

Once the valve body is out, you just need to keep it upright and note all the holes for the check balls. Using the center bolt to hold it up works better, last one out, first one in.

You must use an inch-pound torque wrench to reinstall.

 

[JayArr]

After you've done it you'll look back and wonder what you were afraid of.

There is a ton of literature, posts and youtubes on this, even if you dropped the whole box of parts you could still find out how to reassemble it with some time on the internet.