Hello all,
I've browsed through some posts and don't know that i completely have the answer i'm looking for.
I have a 2001 GMC Sonoma with the 4.3 V6 and a 4l60E. Just replaced the transmission, new fluids , new torque converter.
At cruising speeds i'm getting a 1-300 surge in RPM. It does it with cruise control on and anywhere from 40-65. Doesn't seem to do it at lower speeds. I can hear the engine physically reving.
Common solutions seems to be EGR, TCC Sensor, but TPS.
Thanks in advance for any help.

 

Sounds like torque converter clutch engaging and disengaging. Engagement starts at 45 mph. IIRC TCC subsequently disengages when you drop below 40 mph. Honestly what you are experiencing sounds normal. Maybe your TCC is now working (where it wasn't before). I admit it can be a bit irritating when trying to drive a steady 45-50 mph. Its less upsetting when you know what it is!

 

Thanks Les,
It also does it up to 65mph or so. Is there any fix for it or something i can test to?

 

Sounds exactly like mine (which is a 2001 LT). Power/RPMs is pretty low in 4th OD until you get up to 70mph (about 2100 rpm or so with the TCC engaged). The computer kicks off the TCC when it thinks the engine is pulling too hard at a low RPM. Then in and out if you are driving at just the right speed. Worst at 45. Goes away by 65. I personally believe this TCC operation is programmed simply to keep rpms up to meet emissions requirements, as it would be VERY easy for engineers to program things to correct it. Unfortunantely, the operation is programmed into your PCM and cannot be changed without the ability to modify your PCM programming.

One thing you might think about is the TCC type in the different 4L60e's and the modifications that are done to defeat their TCC problems. Their are several types of TCC friction materials and it's important to have the right kind for your year of 4L60e and any mods that have been done. I'll link to a good article on the subject. It's most important to have a type that will last within your system as it is. Both of our 2001's were PWM-EC3 4L60e transmissions that originally had a torque converter with carbon fiber friction materials. The TCC in unmodified EC3 transmissions slips just a little all the time to soften up the application and generates extra heat that can cause failure of other friction materials.

https://www.sonnax.com/tech_resource...-modifications

The last thing I should mention is that with the 4L60e, it learns to shift correctly and this can take some time for the vehicle to learn a new trans. Normally trans shops clear the memory on this when installing or requilding a trans. Here's another article. The 4L60e is pretty much the same as the trans being talked about.

https://www.sonnax.com/tech_resource...essure-systems

If you get sick of it when driving 45-50, just drive in third gear and prevent the 4th gear from engaging. The TCC will still work, but your RPMs will be just a little higher.

Good luck and let us know what you think!

 

Thanks for all the info Les.
The transmission and torque converter were Chevy rebuilds.
Will a transmission shop wipe the memory on it? Even if its for a fee?
I'll keep an eye on it and update with any changes.

 

Yep, just tell them you want the adaptive learning to be reset. They will know what you want and can probably do it without appointment or bringing your vehicle inside. The disconnect battery and self-help strategies on the Internet will not work for your vehicle.

After it is reset, know that the PCM compares shift time to engine load and will eventually adjust line pressures accordingly, but remember there are about a dozen or so "tap cells" to calibrate for different accelerations on each 1-2 and 2-3 shift. So may take some time to hit and adjust them all.

Alternatively, if it is shifting satisfactory now it will eventually adapt to your new trans just fine without clearing things. Shifts will only get better.

One last thing.... a tip that Transman here on the forum gave me. Lazy shifts (and I imagine TCC operation) can be affected by the MAF sensor. Mine wasn't throwing any codes or seeming to making things run poorly on my 2004 Avalanche with 4L60e. But I cleaned the MAF sensor up good with MAF sensor cleaner and it changed my lazy 1-2 shift completely. It's so simple that it might be worth a try on your TCC problem. Might just make the application of your TCC less noticeable, or not cycle in/out as much - who knows!

 

Just an update for anyone it might help.
Went to a local transmission shop. Had adapt codes cleared for $10.
Surge is 99% gone. Still some small issues.
Going to try cleaning the MAF Sensor this weekend to see if it helps my 1-2 Shift.
Overall worlds difference in the day to day driving.

 

Glad to hear things are working better. Keep us posted. All of us learn from successes.

 

So i've ironed out most of my issues except one.
On early morning trips to work and cruising in cruise control around 60-70 the transmission is wanting to ship between 3rd and O/D.
It doesn't seem to do it in the afternoons and all other gears are shifting great with no issues.
I've through other issues replaced:
TPS
MAF
PCV Valve
Any input from those with more knowledge?