Transmission Help 6.6 2001

[virginiadeez]

My Chev 2001 duramax just turned 220K miles. Truck runs like a champ except that yesterday I noticed when coming to a stop around 10mph the transmission seems to slip everytime. Sometimes light and sometimes kinda of hard. I also noticed that when on a incline waiting on traffic it sometimes slips hard in the rear. I took it to the "local " mochanic" and he change the fluids and found no metal shavings. I guess thats good.

Any suggestions or am I looking at replacing it....any help or suggestions?

thanks,

chris
richmond, virginia
email at thermolok7@aol.com

[virginiadeez]

I have a 2001 chev duramas with 220K. It started to slip or grab yesterday when coming to a stop around 10mph. Sometimes a soft slip and sometimes quite hard. It also does it sometimes when on a incline waiting on traffic. I changed all fluids and found NO metal in the fluid. Am I inn trouble here? Am I looking at a costly replacement trans?

Help!

chris - richmond, va
email thermolok7@aol.com

[Kennedy]

I'm not sure sure why it would have surfaced just now, but there was a programming update for the TCM that referenced what you describe. I would start there.

[DmaxMaverick]

Welcome aboard!

TCM update aside (recommended if it hasn't been done), many, if not most, of this condition can be attributed to "two foot driving". If you do this, try keeping your left foot off the brake pedal. The PCM/TCM requires a specific ground speed and zero throttle input before it commands shift down to 1st for a start from stop. The tranny doesn't actually slip, but tries to start in 2nd gear (because it never actually downshifted to 1st), then shifts to 1st once throttle input and ground speed is sufficient, like taking off from a stop. It sounds and seems like a slip, because the torque converter is taking up the torque while starting in 2nd. The later TCM updates somewhat "softened" the condition parameters to minimize this. If this isn't the case, in your case, I recommend the TCM calibration update before any further attempts to fix something that may not be broke. The update should cost you about 1/2 hour of GM shop time. Some dealers (in the past) would do this at no charge, even if the vehicle is out of warranty.

[virginiadeez]

Welcome aboard!

TCM update aside (recommended if it hasn't been done), many, if not most, of this condition can be attributed to "two foot driving". If you do this, try keeping your left foot off the brake pedal. The PCM/TCM requires a specific ground speed and zero throttle input before it commands shift down to 1st for a start from stop. The tranny doesn't actually slip, but tries to start in 2nd gear (because it never actually downshifted to 1st), then shifts to 1st once throttle input and ground speed is sufficient, like taking off from a stop. It sounds and seems like a slip, because the torque converter is taking up the torque while starting in 2nd. The later TCM updates somewhat "softened" the condition parameters to minimize this. If this isn't the case, in your case, I recommend the TCM calibration update before any further attempts to fix something that may not be broke. The update should cost you about 1/2 hour of GM shop time. Some dealers (in the past) would do this at no charge, even if the vehicle is out of warranty.


Im a one foot driver and my foot is not on the brake and gas. When I am slowing down, EVERY time at 10mph the tranny shifts hard, sometimes softer but everytime. Also, when on a hill holding the brake in it will jump, its like someone hit me in the rear.????

[DmaxMaverick]

OK. I think what you are experiencing may not be tranny shift related at all. At the very least, you have a slip-yoke issue, which is easily correctable. You may have other issues, but fix this first.

(Park on level surface or grill downhill, set E-brake, chock the wheels, etc.) Drop the driveshaft at the rear. Pull the slip-yoke from the transfer case (or tranny, if 2wd). Make a note of the spline and U-joint clock position (reinstall the same). Smear some lithium (or molybdenum, if you have no lithium) grease on the spline, and reinstall. This should take care of that "bump" situation you get when stopping or taking off.

This is caused by the spline not slipping during times of spring-wrap, like when stopping and starting. The spring stores the energy, held there by the bind of the brakes, and is suddenly released when the load is equalized and the spline suddenly slips from one extreme to another. Normally, the spline should slip during the wrap condition. This is a normal condition, and the spline should accommodate it.

Just a SWAG, but my bet is this will cure your problem.

[Kennedy]

Classic symptoms of the issues addressed in the programming update. It basically adjusted the shift speeds. Apparently some times it will stay in 2nd and when you start out it downshifts immediately hence the bump.

Visit a dealer and ask them to update the TCM programming and while he is at it check the ECM progranmming as well.

15175857 0000EF1B New calibration to accomodate overdrive defeat switch and address 2-1 shift quality

[virginiadeez]

Classic symptoms of the issues addressed in the programming update. It basically adjusted the shift speeds. Apparently some times it will stay in 2nd and when you start out it downshifts immediately hence the bump.

Visit a dealer and ask them to update the TCM programming and while he is at it check the ECM progranmming as well.

15175857 0000EF1B New calibration to accomodate overdrive defeat switch and address 2-1 shift quality

It seems to have stopped all this. Could it been that I havent driven it in almost 2 months and a Sol. sticking or something. All the shifting problems went away. Could it be caused by low voltage coming from old batteries?

[Kennedy]

My best advice is to see a dealer and have them check for ECM and TCM programming updates.

Yes old batteries can impact a lot of things, but there are known fixes for known issues specifically related to your symptoms.

Also does your air filter box duct to the inner fender?