SOLVED! Transmission shudder at 50-60 mph

[santon]

Hello guys,
I bought a used 4L60E together with its torque converter and paid the mechanic to replace my blown transmission. The mechanic installed this "new" transmission together with its torque converter and added some ATF. He did not replace the filter and the old ATF; I planned to service the transmission later, after checking that everything works properly. It seems that the "new" transmission shifts good. However, I noticed a shudder at 50-60 mph. If I accelerate or press on the brake pedal, the shudder stops. I am using the Torque application and can observe the TCC slip. It seems that the shudder occurs when the torque converter clutch (TCC) is engaged. There are no error codes, at least there is no "check engine" light and the Torque application does not show any errors. The shudder definitely comes from the transmission. There are no misfires, the engine works good. I suspect the bad TCC. How can I know for sure that the problem is within the torque converter and not related to something else (valve body, etc)? I have a good torque converter but cannot replace it by myself, so I will need to pay the mechanic for this job again.

 

[santon]

An addition to my previous post- I tried to "refresh" the ATF today. Using an electric pump, I removed 2 quarts of ATF through the dipstick and replaced them with a new fluid. After driving for some 25-30 miles, I removed an additional 3 quarts and replaced them with a new ATF. I was hoping that the fluid renewal will reduce or eliminate the shudder; however, I did not see any improvement. I thought to open the pan and do a normal transmission service tomorrow (to change the filter and the fluid) but I will probably wait with this.

 

[budwich]

You can try leaving the gear shift in 3rd and taking a drive. Again, watch your torque app for the slip result. What should happen is the torque converter should lock up again in third but it will be at a higher "equivalent" rpm compared to "D". From there, you should be able to move your speed thru some different areas and feel any differences. Go from the result.

Hope your "new" tranny wasn't a "old bad" tranny... :-(

 

[santon]

You can try leaving the gear shift in 3rd and taking a drive. Again, watch your torque app for the slip result. What should happen is the torque converter should lock up again in third but it will be at a higher "equivalent" rpm compared to "D". From there, you should be able to move your speed thru some different areas and feel any differences. Go from the result.

Thanks! I tried to drive in 3d and did not notice any shudder. The torque converter locks. The shudder occurs only in 4th. I will try to check it again tomorrow.

 

[budwich]

Yu might check the u joints near the tranny to ensure they were tightened up during the replacement. Hopefully, someone with more tranny experience will come be. My only experience with a problem was in a ford ex which had clutch pack problems (rad fluid ingression) which initially had shutter and then I found out why ... :-(

 

[TJBaker57]

Have a read through this article, some of which applies to our transmissions. See if the the part about the worn TCC valve bore sounds like it applies to your trouble.

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

 

[Mooseman]

Sure does sound like the TCC. I'd do a full service on the tranny (fluid and filter) and check the pan for metal debris beyond the usual black filings. This should eliminate any issues with fluid pressure.

After that, there is the Lubegard 19610 additive that people swear by and that I have used for a slipping TCC in a 6L80.

Lubegard 19610 Dr. Tranny Instant Shudder Fixx, 2 oz. Red : Amazon.ca: Automotive

Lubegard 19610 Dr. Tranny Instant Shudder Fixx, 2 oz. Red : Amazon.ca: Automotive

www.amazon.ca

If it's still there, there are PWM elimination kits that will send full fluid pressure rather than slipping the TCC with PWM:

4L60E valve body upgrade kit, AKA P1870 "code buster"

Skip to the bottom if you don't want the back story. Technical Stuff and Background: I've had a bit of a history with the GM 4L60E transmission and dealing with some of the shortfalls of it. Over all, it is a good transmission, but it has a few weak points. A semi-common issue with the 4L60E is...

gmtnation.com

After that, I'm afraid that a tranny drop to replace the TC will be required.

 

[santon]

How can I differentiate the bad TC from the problem with the valve body/PWM? Does the bad PWM valve always throws a code (P1870?)

 

[Mooseman]

Only way would be to drop the valve body and repair the TCC valve. Personally, I'd just do the mod.

 

[santon]

Only way would be to drop the valve body and repair the TCC valve. Personally, I'd just do the mod.

Well, it seems that I have only 2 options now:

1) drop the transmission and replace the TC. I have a good TC that worked fine on my old transmission;
2) replace the transmission for another one- the guy that sold me this transmission should give me another one since the "warranty" period had not expired yet. I will also install my good TC at the same time.

Both options will cost me the same price of transmission removal/installation. I would like to know what need be replaced now, but since I don't have any DTC, I can only guess here.
If the problem will persist after TC or transmission replacement, I will probably consider the valve/PWM delete mod. It seems that the mod could be done without transmission removal from the vehicle. I have also seen that it is possible to install the upgraded TCC valve without removing the valve body but I think that was true for the older versions of 4L60E. As I understand,. the mod mechanically obstructs some fluid passage, eliminating the smooth PWM control of the fluid pressure to the TCC and converts the operation of the TCC to that of the old school way- the TCC will either be unlocked or locked. Is it possible to do this by tuning the PCM? I mean commanding the TCC solenoid to be either fully open or fully closed?

 

[Mooseman]

Is it possible to do this by tuning the PCM? I mean commanding the TCC solenoid to be either fully open or fully closed?

Yes, in fact, I have done this to all of mine except my 2021 Sierra. Can also get some other things done to improve engine performance and shifting at the same time. If you don't have the software or somebody to do it for you, we have @limequat that does it for just $99. His site is http://www.lime-swap.com/

 

[Reprise]

I'd even go so far as to say that it's probably more the TCC valve than the thing it controls (the torque converter). Get it tuned out, or get one of the remediation kits (Sonnax and TransGo sell them; there are others). Many here have installed the transgo kits, and they have worked for years afterward.

Keep in mind that to install it will involve removing the valve body (drain / remove pan to get to it). If you can follow instructions, are moderately mechanically adept, and have some basic tools (socket set and ratchets), you can install the kit as a DIY.
If you don't feel comfortable doing it, a decent mechanic should be able to (the 4L60E transmission was installed in many vehicles that were US export, so there should be someone in Israel that could do it).
If not... contact Limequat, as above, and send him the Engine Control Module (ECM). He'll have it back in your hands in a few days. Again... many of us have used his services, so he's trusted (and a member) on this site.

 

[santon]

An update - my friend has the HPTuners and we modified the tables for the TCC control. We set the minimal PWM to 90% and the maximal PWM to 100%. This solved the problem! There is no shudder anymore. The TCC locks firmly without any slippage. I am very grateful to you guys, you helped me to solve this problem. This forum is amazing!