Removed PWM control from TCC

gmcman

Original poster
Member
Dec 12, 2011
4,658
The TCC (Torque Converter Clutch) uses a PWM control for applying lockup. This can and does wear the clutches in the TC and I began looking into this after I experienced a shudder when towing my 14' trailer. Not only that the trans has 183K on it so I would like to keep it working as long as possible.

When the TC locks and this is when I'm in 4th (OD), the RPM's will fall about 2-300 RPM's which is normal, but when I'm around 45-55 there is still some slight rise in RPM's sometimes when the lock has occurred...about 50-100 RPM and is fully locked around 58-60 and above. I don't know if this is normal but the TransGo PWM eliminator valve takes away this PWM control and makes the TCC either fully lock, or disengage.

The ECM still sees the PWM control but when the fluid is channeled, the TCC locks solid despite what the PWM TCC solenoid is doing. The ECM thinks it's still performing a variable control but it's not so there is no codes.

This involves removing the valve body and removing the TCC valve and replacing with the TransGo valve and spring. Also you ream the hole in the separator plate to allow more fluid to the TCC, thus increasing holding power.

I can say it's definitely different but I like it, very pronounced lock and it doesn't let go unless of course you let off the gas, tap the brake, or really put your foot into it. Business as usual for the lockup but it's much more pronounced and not harsh at all.

Having the 4:10 ratio I can't say how it would work with the 3:42, may lug it a little around 45 MPH but when I'm cruising at 40-45 it's locked at about 1400-1500 RPM, this may help the city mileage..jury is still out.

I did take a vid of the tach after the change but not before, sorry..I'll post that later.
 

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Sparky

Member
Dec 4, 2011
12,927
This works just fine on a 3.42 truck.

I used a Transgo kit which had a bunch of other stuff along with some Sonnax parts as well, a very well laid out kit by an ebay seller ctpowertrain. Anyway, I wasn't having any trouble with mine BUT I know the 4L60E has a tendency to have problems with that TCC PWM junk. My old car had a 4L60E and was having all sorts of trouble and this kit fixed it, so for preventative maintenance I installed it in my Trailblazer. That was back 56k miles ago and its flawless.

The lockup almost feels like a 5th gear shift on mine, while stock as everyone knows it is a rather mushy slide into lock and I never cared for that. More slippage = more wear.
 

ScarabEpic22

Member
Nov 20, 2011
728
Yep, good stuff.

Although changing the tune to do this is a little easier, get 95% of the effect with a few key strokes. If you've already dropped the valve body, definitely worth it. Otherwise just have your tune changed (and you should have it changed after this now too). :thumbsup:
 

Sparky

Member
Dec 4, 2011
12,927
In some cases the valve body is worn a bit and you have to replace the TCC valve with a new one to actually fix the problem. That's what was going on with my old car's transmission.
 

dfc739

Member
Jul 29, 2012
170
Des Moines, IA
I was also having problems with my torque converter lock back last summer. I took it to a transmission shop and they said it would be at least $500 to fix. I fixed this issue and more for about $100 (including buying the small torque wrench). And I love the way the "fifth gear" feels and holds. Now I just need to save money for a tune...
 

gmcman

Original poster
Member
Dec 12, 2011
4,658
Sparky said:
I used a Transgo kit which had a bunch of other stuff along with some Sonnax parts as well, a very well laid out kit by an ebay seller ctpowertrain. Anyway, I wasn't having any trouble with mine BUT I know the 4L60E has a tendency to have problems with that TCC PWM junk. My old car had a 4L60E and was having all sorts of trouble and this kit fixed it, so for preventative maintenance I installed it in my Trailblazer. That was back 56k miles ago and its flawless.

The lockup almost feels like a 5th gear shift on mine, while stock as everyone knows it is a rather mushy slide into lock and I never cared for that. More slippage = more wear.

I used the Transgo kit as well this time.

I also added the vette servo, seperator plate, 1-2 & 2-3 accumulator pistons, and both shift solenoids about 10K miles ago since I had a slight 2-3 flare, fixed that up like new. I highly recommend at least that for these transmissions that have around 150K just for preventative maint.


Sparky said:
In some cases the valve body is worn a bit and you have to replace the TCC valve with a new one to actually fix the problem. That's what was going on with my old car's transmission.

That very well could have been the case with mine, I wasn't taking any chances though...sooner the better.

Here's the vid, nice my exhaust is slowly becoming swiss cheese so the engine note is easily heard. First run was at light throttle, 2nd with more load.

[video=youtube;iQqNy2Zf2fU]http://www.youtube.com/watch?v=iQqNy2Zf2fU&feature=youtu.be[/video]
 
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Metsämies

Member
Mar 28, 2012
15
gmcman said:
The TCC (Torque Converter Clutch) uses a PWM control for applying lockup. This can and does wear the clutches in the TC and I began looking into this after I experienced a shudder when towing my 14' trailer. Not only that the trans has 183K on it so I would like to keep it working as long as possible.

Usually the TC clutches are good. People often think they wear out first, remember they are ment for high friction high torque applications. What the cause of this worn clutch feel is wear in the valve body because of the PWM. It's due to wear in the valve body bore around the TCC PWM valve. In stock form, the steel spool valve rides in the Aluminum bore in the valve body. After a few years of cycling, the bore wears (obviously, being the softer of the two metals). This contributes to less than full apply pressure being commanded of the actual TCC valve, and subsequent tq. convert clutch shudder, falling out of lockup, the feel of a worn TCC.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
So I have the typical 200-300 rpm flutter when in lockup and doing about 50-55 mph. It's annoying at best. So what trans kit do I get to either eliminate the pwm or do a more entailed rebuild with the plates from the earlier post? This is something I can definitely do myself and not pay a mechanic for. My exhaust is getting swissy to and a clear growl when in lockup and low rpm. I would like to know where parts can be obtained and if any special tools needed to do the job.
 

Sparky

Member
Dec 4, 2011
12,927
Get this:

4L60E 4L65E 1996 2006 1870 P1870 Code Buster Combo Kit Corvette Servo Kit Book | eBay

That comes with everything you want except for fluid and filter. New hardened valve body separator plate, new TCC PWM eliminator valve, upgraded springs and servos, the works. That's what I put in mine. I wasn't having problems yet, but my old car (with the same trans) did. I now have 191k on my truck and still going strong :biggrin:
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
Sparky said:
Get this:

4L60E 4L65E 1996 2006 1870 P1870 Code Buster Combo Kit Corvette Servo Kit Book | eBay

That comes with everything you want except for fluid and filter. New hardened valve body separator plate, new TCC PWM eliminator valve, upgraded springs and servos, the works. That's what I put in mine. I wasn't having problems yet, but my old car (with the same trans) did. I now have 191k on my truck and still going strong :biggrin:

Does this have the same drive ability with this kit or will it be all wicked and hard shifting. We live in a snowy environment and don't need that hard shift chirp effect that so many love. Also reading other posts, curious about the check balls when you drop the valve body. Did they go falling out everywhere or did the plate keep them in until u took out the plate? Read a real nice post with great pics but didn't mention the check balls, only when putting back in to use Vaseline or trans grease

- - - Updated - - -

Sparky said:
Get this:

4L60E 4L65E 1996 2006 1870 P1870 Code Buster Combo Kit Corvette Servo Kit Book | eBay

That comes with everything you want except for fluid and filter. New hardened valve body separator plate, new TCC PWM eliminator valve, upgraded springs and servos, the works. That's what I put in mine. I wasn't having problems yet, but my old car (with the same trans) did. I now have 191k on my truck and still going strong :biggrin:

Does this have the same drive ability with this kit or will it be all wicked and hard shifting. We live in a snowy environment and don't need that hard shift chirp effect that so many love. Also reading other posts, curious about the check balls when you drop the valve body. Did they go falling out everywhere or did the plate keep them in until u took out the plate? Read a real nice post with great pics but didn't mention the check balls, only when putting back in to use Vaseline or trans grease
 

c0a8l0v6i8n9

Member
Mar 6, 2013
93
I did this to my truck as well. Not hard chirping shifts but you can feel it shift. The check balls stayed in the valve body and I did not drill the plate.
 

Sparky

Member
Dec 4, 2011
12,927
dla442 said:
Does this have the same drive ability with this kit or will it be all wicked and hard shifting. We live in a snowy environment and don't need that hard shift chirp effect that so many love. Also reading other posts, curious about the check balls when you drop the valve body. Did they go falling out everywhere or did the plate keep them in until u took out the plate? Read a real nice post with great pics but didn't mention the check balls, only when putting back in to use Vaseline or trans grease

You can tell the shifts are a tad firmer but it isn't what I would call hard at all. That kind of shift firmness change is reserved for the HD-2 kit. This kit is just meant to fix weak points more than anything.

My check balls sat either in their sockets or sat on top of the plate as I lowered it. Just keep it level when dropping it down.

You don't have to drill the plate. The replacement plate already has some holes resized vs the stock plate. I think I did do a couple of the optional drills but that's entirely up to you.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
Sparky said:
You can tell the shifts are a tad firmer but it isn't what I would call hard at all. That kind of shift firmness change is reserved for the HD-2 kit. This kit is just meant to fix weak points more than anything.

My check balls sat either in their sockets or sat on top of the plate as I lowered it. Just keep it level when dropping it down.

You don't have to drill the plate. The replacement plate already has some holes resized vs the stock plate. I think I did do a couple of the optional drills but that's entirely up to you.

Just one more question. The corvette servo? Same for the trailblazer? Blue/red o ring etc...in the kit but why does it say corvette servo. I'm assuming for corvette but I seen it was used in the envoy on prior post. What's the difference or is it just the name
 

Sparky

Member
Dec 4, 2011
12,927
dla442 said:
Just one more question. The corvette servo? Same for the trailblazer? Blue/red o ring etc...in the kit but why does it say corvette servo. I'm assuming for corvette but I seen it was used in the envoy on prior post. What's the difference or is it just the name

Just a name. It is called that because it is a replica of the servo they use in the Corvette's transmission. More holding power. That's all really.
 

gmcman

Original poster
Member
Dec 12, 2011
4,658
dla442 said:
So I have the typical 200-300 rpm flutter when in lockup and doing about 50-55 mph.

Is this happening when under load without lifting off the gas pedal? The RPM should drop 2-300 when the torque converter (TC) locks, and will unlock if you lift off the gas pedal. The drone you get is the lower RPM load but if the RPM's will somewhat stay put under load with slight pressure on the gas pedal then the torque converter clutch (TCC) is holding. When the TCC is locked, keep steady pressure on the gas and simultaneously tap the brake....do the RPM's rise 2-300? If so then that's normal.

What I and others have done is replaced the PWM (variable) control of the TCC with an on-off style engagement known as the TCC PWM eliminator kit and when the TCC locks, it locks right now and feels like another gear.

The vette servo will help if you are getting a soft 2-3 shift or if severe enough, a 2-3 flare which is actually excessive clutch slipping.

Both mods are highly recommended.

If I had to do it all over again, at the same time you add the vette servo, add the Sonnax super hold servo for the 3-4 clutch pack, which is the weak link in the trans, next to the sunshell but is far easier to upgrade. The super hold servo installs under the same cap as the vette servo.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
Sparky, I got my power train kit from eBay today. Lots of parts. Are they all to be used, just curious. There is a big round part 77772b with the kit which don't look to be used in any threads. I'm thinking that there are going to be some let over parts with this kit? Right?
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
dla442 said:
Sparky, I got my power train kit from eBay today. Lots of parts. Are they all to be used, just curious. There is a big round part 77772b with the kit which don't look to be used in any threads. I'm thinking that there are going to be some let over parts with this kit? Right?

I see that the large round one is the corvette servo. Did you replace the o-rings on the pin as we'll. and what makes this "corvette" part different from the oe part? The spring? Or is the actual design of the new parts that install with the pin? Is it necessary to replace the servo at all? Also, I seen in some other posts on the pinless accumulators they drove in a ball bearing and seated it in with a chisel on the housing. On this eBay kit, there is no mention of doing is at all in the instructions. Perhaps their trans was older than my 2005? When installing the pin less accumulators, do I have to do this ball bearing step. I wish these instructions from transgo were laid out better and not so boggled together. A lot of parts with this kit and not very good instructions to go with it.
 

Sparky

Member
Dec 4, 2011
12,927
OK a few things to hopefully clear it all up.

This kit from this ebay seller is just a collection of 4L60E upgrade parts, which is why it has a bit of a "cobbled together" look. That is also why there is no single instruction sheet/booklet. The main one is the Transgo one (which yes it is a little bit disorganized, I recommend looking it over completely before you start the process and double check each page as you do the work). Then in the boxes for the pinless accumulators there should be the ball bearing and brief direction sheet for it.

The Corvette servo is used if you want (I do recommend it). It is a little different design than the original that increases holding power, along with the spring changes that come with the Transgo part of the kit. It is a bit of a bear to get to given its location, and a prybar or two is useful to get the leverage needed to compress the cover when removing the snap ring and when reinstalling the cover and snap ring. It isn't 100% necessary to do it at all, but if you can I would. I know some people don't because it is a pain to get to. I had my truck up on a lift when doing the work so that made it a fair bit easier. I did have to partially lower the trans by loosening the cross member.

If there is a new O ring for any particular part, use it, otherwise you reuse the existing. A new O ring and seals should have come with the vette servo for the servo itself and the cover O ring (the old ring tends to get messed up when you pull the cover).

Mainly I followed the transgo kit directions, but swapped the other parts in as I came to them (vette servo, pinless accumulators, new screens and separator plate, etc). I took stock of which new additional parts went where so I wouldn't miss them as I went along. There really are only a couple spots for that - the accumulators can all be done at the same time, then the vette servo on the side. Separator plate/screens are pretty obvious when you do those as you need the plate and seals when you put the valve body back together.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
ok, the seperator plate instructions says to drill but dont have too. I under the assumption that to drill it makes it shift harder otherwise leave it alone. i may attempt the servo after i get valve body done as thats the main problem with the pwm valve. some things I have seen with the acc.pistons are the ball bearing was seated with a punch and ntched at the top..i suppose that info is going to be in the package of the pistont hat I have not opened up yet. Looks like 3 pistons came with the kit. all can be used or extra one in there? Appreciate the input and sure when I start gettin into it it will make more sense on some of the parts. Plan on doing it next weekend, so I will advise.
 

Sparky

Member
Dec 4, 2011
12,927
Yeah drilling increases shift speed, but it isn't a huge difference IMO.

There aren't any spare accumulators, they included the count you need for the trans. All are used.

Once you have all the parts in front of you and the trans valve body open it makes more sense.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
One more question on the servo. The transgo says to get a number off the 2nd piston so it can be matched to the accum bushing code for the proper colored spring. Is this number from the old piston being replaced or the new piston from ct power train products. The number on the new does not jive. Further on the new transgo separator plate there are spots supposed to be drilled to .093. I thought the plate came ready to install. I am guessing these holes need to be drilled per the instructions. They appear only to be bit smaller than the drill provided.
 

Sparky

Member
Dec 4, 2011
12,927
The holes are stock size. The kit recommends the changes. I drilled it, but you don't have to.

I matched the springs to the original piston, then replaced the piston.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
Ok..tomorrow is the big day for the kit. Admit I'm a bit nervous but I'm sure following the directions I'll be ok. Just a bit concerned on accessing the servo while transmission is in. Easy to drop it down a bit for me area to work in? I'll be on my back with the TB up on jackstands..ug.
 

Sparky

Member
Dec 4, 2011
12,927
Not hard to drop down, but be mindful of the trans cooler lines connected to the side that you don't snag/kink them. Not sure if that is much of a potential issue or not, I had my lines removed when I did it since I was replacing them.

I had the benefit of doing it at my friend's work on a lift, so I had it easy. Be careful under there.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
HUGE QUESTION.I TOOK OFF THE POWER control solenoid, pulled the clip and oops. Under spring tension and cap shot out with the spring. Found the cap but spring unknown. Did find a spring in the bag of other springs that was open and facing me and it could have shot in there . The spring in this eBay kit from cb power train that could be the lost one is black, matches same height of the spring according to the blue manual included. Has the same amount of twists in the spring and is black. Same diameter as the cap wit he c-clip too. Seems to fit in well and has tension when cap pushed in to put in the c clip. This this spring is it or is it coincidence that the kit( from the transgo orange box) is the same but a different spring tension that will not work. Also the accumulator in the trans case had a larger pin and called for the yellow spring and to seat the larger two balls into the case, correct? Any help on the power control solenoid spring behind the cap would be appreciated. Also the spring looks like the one in this post. offroadTB.com - View topic - Shift kit install. Anyone ever have a black spring left over from the trans go kit ?
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
We'll..it was the spring..no other choices. Put all together, filled it up no leaks. First to second sure is a firm shift and full throttle it makes the serp belt squeak. 2-3 shift a bit quicker than before and 3-4 shift ok too. The rpm fluctuation is gone and stays in lockup. Time will tell as it is driven more. Put about 50 miles on it already. The servo was a pain in the ass, no room but got it out and had another set of hands to help keep it pressed in whole the ring was put back on. All being said, taking my time and making sure each step is complete the kit was not hard, just time consuming and double tripple check work and steps. Put about 8 hours total into the job. Thanks for the posts and will update as the TB is driven more.
 

Sparky

Member
Dec 4, 2011
12,927
Sorry wasn't online to ask. Yes that sounded like the spring to me too.

WOT 1-2 makes my belt chirp too but I figured that is more due to having an original tensioner still that may be getting a little weak after all these years.

Glad it is all back together, yeah that servo can be a bit of a nuisance. What you describe how it behaves so far sounds good to me. I noticed on mine it smoothed out a tad after a "break in" which is probably more the computer adjusting itself to the new internals a bit.
 

Mooseman

Moderator
Dec 4, 2011
25,660
Ottawa, ON
Just reviving this stale thread to add a bit of info. I just did mine as the shifts were getting sloppy. Had the kit since last year but just got to it now. I got the one from CTPowertrain off eBay with the Corvette servo. I did everything except the servo as I wasn't able to get the cover off. I have an aftermarket cat and it's right in the way of that cover. I just guessed that I had the 553 servo in it with the DX valve and used a yellow spring in the valve (as per this write up at offroadtb ).

I was nervous as heck, thinking I might have screwed up something. I almost did forget to put the check ball in the case. Took my time, double checked everything. Took me 12 hours. One thing I did that helped minimize the mess was to pump the fluid out using the hose from my tranny cooler (the method used for flushing) and a large metal pan instead of a tarp (kinda looks like a giant cookie baking sheet).

I have to say that I am very pleased with the results, even without the Corvette servo. 1-2 shift is solid, 2-3 and 3-4 is more "precise" (less mushy) and the TCC PWM is gone (YES!). I also had a dead spot or slippage when coasting and giving a bit of gas, as if it was not in gear until I gave it more gas where it would engage. That's fixed too.

If I ever have to remove the cat, I'll give the servo another shot but for now, I'm giving this :2thumbsup:
 

Sparky

Member
Dec 4, 2011
12,927
Mine has over 80k miles on the install and still great. The fluid looks almost new still which is probably helped by less heat generated from the factory mushy shifts and converter lock.
 

Mooseman

Moderator
Dec 4, 2011
25,660
Ottawa, ON
Driving it a bit more today, I found the 1-2 shifts at part throttle a bit harsh, throwing me back in my seat and the truck lurching. Could be because I also have a tune.
 

Sparky

Member
Dec 4, 2011
12,927
Did you have a "shift level x" tune on yours from PCM? Mine has a stock tune on everything and it feels good. I think the transgo setup is designed around stock shift firmness.
 

Mooseman

Moderator
Dec 4, 2011
25,660
Ottawa, ON
Yeah, I got a level 2 in the tune so it must be compounding the firmness. I could swap my PCM for a junker spare I picked up just for a test (after a security relearn). It would also bring me back to the good 'ol days.
 

gmcman

Original poster
Member
Dec 12, 2011
4,658
Hey Moose, I would like to suggest that when you add the vette servo, go with the Sonnax Super hold servo as well since you will have it all out. This will increase the hold on the highly vulnerable 3-4 clutch pack. It's a pricey little booger but I would do it. I have one just haven't installed it yet but I will soon.

The best way I know to access the cover for those apply pistons, is to lower the trans crossmember. This is very easy especially if you have an impact. There are four forward facing bolts I believe and you remove both pass side and the inside drivers side, just loosen the drivers outer bolt. Then remove all the upward facing bolts.

I placed a jack under the crossmember just in case but it didn't fall the least bit, took a pry bar to lower from the pass side and being mounted to the tailshaft keeps it from falling. I lowered it about 4" and the cover was easily accessible.

Before you remove the cover, take a wire brush and go around the snap ring then blow off the dirt. Once you remove the snap ring hit it with the brush again. This will lessen the chance of grit entering the clean area of the bore. Use the prybar and push in the cap a few times against the spring before you pull the snap ring.

Make sure you keep it clean, hard to see in there.
 

jimmyjam

Member
Nov 18, 2011
1,634
mine apparently has sonnax 4th and fairbanks 2nd servos in it.
IDK what the servo's affect is on the clutch pack, its purpose is to engage the band on the reverse input housing on the 1-2 and 3-4 shift. My first trans rebuild at around 45k miles was from smoking the 2-4 band
 

Mooseman

Moderator
Dec 4, 2011
25,660
Ottawa, ON
I knew about lowering the tranny but the cat is really in the way, directly below the tranny, not like the original which was a little forward and angled. Lowering the tranny would put the servo cover directly next to the cat.

The servo I got was the Corvette type in the kit from CTPowertrain. If the opportunity presents itself, I'll install it.
 

Mooseman

Moderator
Dec 4, 2011
25,660
Ottawa, ON
I installed an original PCM, security relearned it, worked fine except for the CEL for the CASE relearn (not essential) and fan errors (which I don't have). The shifts have changed a bit, seems the 1-2 is just a little less hard at part throttle and other s seems a little bit slower. When going to WOT at 50mph, the downshift is slower. When going WOT from 0mph, the 1-2 shift makes my belt chip (like others have noted). Didn't have that with the tuned PCM :confused:

Anyway, I'll leave it in there for a while for a good comparison. I also want to compare for MPG's between the two PCM's because I will be putting it back eventually.
 

dla442

Member
Mar 31, 2012
249
grand rapids, mi
Mine is still going strong and shifting quick and tight on first. The overdrive feels like a new gear and snaps right out when a little gas given. Very pleased with this fix so far. I did the corvette servo and yes a pain in the ass to reinstall with the snap ring on the cover. My hands too big... But got it. I think for those dwelling on the corvette servo..you can go without as after the whole kit is installed and plate drilled, that gives plenty of shift. I'm thinking of redoing the servo. That first gear feels like I'm being rear ended it shifts so hard. And btw the customer service reps for ctpowrtrain are complete assholes. I simply asked if I could skip the servo and they argued with me and would no give advice saying the kit is all designed together and won't work right if I don't use it. Full of crap and a waste of air..the guy was so unfriendly.
 

Sparky

Member
Dec 4, 2011
12,927
...Except they sell the same kit without the servo lol
 

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