Transmission feels like it is slipping.

mrwitty_1

Well-Known Member
For sometime now I have noticed what feels like the transmission is slipping in my 2003 Envoy XL. It's hard to explain but it seems to occur under very light throttle on level or when just letting off the throttle when in overdrive, the tach does raise slightly but you hear the exhaust change sound. If you accelerate there is no increase in rpm without speed increasing as if the transmission is slipping. I had this same problem with my 2002 Envoy also. I tow some with the truck and never have a issue with slipping or overheating. I recently serviced all fluids with the exception of the transmission as the pan is rusted and I ordered a new pan. I planned on replacing the 1-2 and 3-4 solenoids along with filter and fluid. Has anyone experienced this or direct me in what is the cause and repair.
 

Mike534x

Well-Known Member
Does the fluid still have that red color, or is it brown and burnt? How many miles are on your Envoy?

If you could post a video of what its doing that would be great too. The last time I drove a car with a slipping trans the RPM would climb or the shifts would be pretty rough. The solenoids usually throw a code when they're bad, but it doesn't hurt to change them out.

@RevHardGarage Knows his way around the 4L60E, so he may know whats going on.
 
D

Deleted member 20902

It almost sounds like you have an issue with the pwm solenoid for the TCC. but a video would definitely be helpful.
 
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mrwitty_1

mrwitty_1

Well-Known Member
Thank you all for the quick replies. The fluid is still red but not as bright as new fluid. It doesn't have any burnt smell and the truck has approximately 75,000 miles. There has never been any transmission codes. I will try and get a video but it only occurs at random times. Maybe just replace the pwm solenoid when I have the pan down, looks like it installs easy like the 1-2/3-4 solenoids.
 
D

Deleted member 20902

Thank you all for the quick replies. The fluid is still red but not as bright as new fluid. It doesn't have any burnt smell and the truck has approximately 75,000 miles. There has never been any transmission codes. I will try and get a video but it only occurs at random times. Maybe just replace the pwm solenoid when I have the pan down, looks like it installs easy like the 1-2/3-4 solenoids.
It is very simple to do a pwm bypass, you can look online to find a tutorial. But basically you remove the pwm solenoid, and grind one edge of the nose flat, this allows the fluid to pass through and not be regulated by that solenoid. The computer thinks it's still doing its job because it's still there and plugged in. This will make the TCC engage more firmly like catching another gear, but there will be no more slippage. The crazy thing is GM programmed the tcm to maintain 20% slip all the time when locked. You will probably notice a slight mileage increase as well 1-2 mpg hwy.
 
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mrwitty_1

mrwitty_1

Well-Known Member
Thanks to the great minds on this form I have been doing alot of reading on the pwm solenoid. From many of the articles I have read it describes my problem spot on ! Now the confusion of which way to correct the problem is the best. I feel the by-pass would be the best solution but from research that also can be done many ways, one way simply removes the solenoid, remove the lower o-ring, cut a slot in the lower section of the solenoid and replace. Seems to simple. Second option is the A74741QA Fitzall/Teckpak valve little more complicated install. What methods have been used by other members ? Pros and Cons please. I really hate to do something that will cause a DTC. Thanks again !
 

Reprise

Lifetime VIP Supporter
Hmm... before @RevHardGarage mentioned it, I wasn't aware of the bypass procedure (meaning that I hadn't seen it discussed here, and prolly no one else on this site was doing it). If I were going in again, there's a good chance I'd try putting it in. Maybe the next time I change the filter - ?

The beauty of it is that the (stock) part itself is pretty cheap, relatively speaking. You could easily get a second one, do the grind, put it in, and if you don't like it (or mess it up)...you still have the old one. Or, to address your concern...DTCs can be fixed, especially if you know what caused it. :twocents:

Given the ease / low $ of a stock solenoid... that Fitzall thingamajiggy better be practically free, if it's even more difficult to install (I haven't looked at it; that's just a 'top of my head' thought)
 

Mooseman

Moderator
It would be great if @RevHardGarage could post a pic of the modified solenoid.
 

cornchip

Well-Known Member
I'll try this out in the spring and report on my findings...but it might be too late for my 4l60. I've been slipping in lock up for the past year. So I made the decision to not ever use 4th. The majority of my driving is below 60mph....and OD isn't needed. I'd love to see 4th back and not code.
 
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mrwitty_1

mrwitty_1

Well-Known Member
Finally got around this past week to finish up the transmission fluid flush, filter change and correcting the transmission "slip feeling". A BIG Thank You to RevHardGarage ! You were spot on with the PWM for the TCC. I went with the Fitzall TCC valve replacement, hardest part was removing the retainer clip without removing the valve body but with time and patience it was accomplished. While I was there replaced the 1/2 and 3/4 solenoids as they were border line on ohm specs, all other solenoids were within spec. The truck now shifts much stronger and after warm up and in fourth gear the converter locks at 35 mph and feels like it has a fifth gear with zero TCC slip. Was well worth the $13 for the vale kit. Thanks again for all the replies.
 

gmcman

Well-Known Member
Good to hear the trans is working as expected. I didn't see this thread earlier but wanted to mention that when the converter is locked at a steady cruise, if you lift your foot the converter will usually unlock and the RPM's will raise slightly. Once you apply steady pressure again on the accel pedal, the converter will lock again.

Not sure if this is what you were experiencing at first.
 

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