GMC Transmission Problems

[tiggerluke]

okfine

[tiggerluke]

Thank you for your reply. I guess it's just upsetting to me that GM would build a tranny with the 2/3 clunk. The 1/2T Yukon doesn't have the same clunking noise, but the dealer said this is probably because of the Yukon's extra weight. Dealer said if I pulled a trailer then it would not happen. But what is really NOT going to happen is finding me pulling a trailer around town just to make my truck shift smoothly.

Thanks again for your feedback

[icedawgs88]

I notice in my new gmc sierra 99 that it shifts a bit to hard. My grandpa owned a 99 silverado didnt have this problem though. Both same trucks but i have no explanation to this. Also notice when taking off from stop light seems to skip alittle bit and not bite right in like it should(only when getting on it) Other than that its fine but not sure if this truck should be shifting this hard and doing that off take off. (tranny fluid is still bright pink)

[scrapdaddy]

Originally Posted by icedawgs88

I notice in my new gmc sierra 99 that it shifts a bit to hard. My grandpa owned a 99 silverado didnt have this problem though. Both same trucks but i have no explanation to this. Also notice when taking off from stop light seems to skip alittle bit and not bite right in like it should(only when getting on it) Other than that its fine but not sure if this truck should be shifting this hard and doing that off take off. (tranny fluid is still bright pink)

these are the least of your probs go buy a dodge or a ford or......toyota or nissan and see the probs u get then ive owned chevys all my life and im 38 nevr had a serious prob with any of em. and ive had a new one every 2 years

[MyTOY]

Bulletin No.: 01-07-30-023B

Date: March, 2002

TECHNICAL

Subject:
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set
(Replace Valve Body)

Models:
1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999-2000 Cadillac Escalade
1996-2000 Chevrolet Camaro, Corvette
1996-2000 Pontiac Firebird
1996-2000 Chevrolet and GMC Light Duty Truck Models
1996-2000 Oldsmobile Bravada
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 2000 (Julian Date 0015)

This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 - Transmission/Transaxle).

Condition

Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.

Diagnosis

Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.

The scan tool may show a DTC P1870 set as a history code.

A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).

Cause

The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.

Correction

Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.

[tykrz]

The 4L60E is basically the old THM350 and the 4L80E is the old THM400 but computerized.

With the 2-3 upshift clunk, do the 2 wheel drive versions have this problem too or is it just the 4x4?

[StevieRayB]

My 2004 GMC 1500 Z71 transmission lost Drive and Overdrive at 73,000 miles. It's a pain to drive 45 miles home in 2nd gear on an interstate, but I did it. The original dealer really tried to do something for me, but since I was over 60K miles there wasn't anything they could do warranty-wise. They did tell me that if I purchased a new transmission from them, the cost would be $2,100 without labor. Now this transmission would be guaranteed for 3 years/100K miles - that's better than the factory! I went to another place for an estimate. The transmission repair shop asked me what year and model truck I had and he told me the problem before I even told him! He said that this was about 70% of his business and that GM definitely knows this is an issue. He rebuilt it for me at $1,500 and replaced the transfer valves with a heavier duty capacity than the OEM. He stated that this was the root cause of my problem. The truck now shifts better than it ever did, even new, and I've gained an increase in MPG.

Figuring that I am a good citizen watching out for the public good, I wrote an e-mail on the GM website explaining this problem under the "Concerns" topic. The answer I received from the Customer "Service" supervisor was in effect - "We're sorry your warrantee didn't cover this". I wrote back stating that I knew that, told them to forward the message to someone who would respond and told them that this is why their stock is junk - they're not listening to their customer base. I received another "We're sorry your warrantee didn't cover this", and that they would not respond to any further messages on this subject. Now that prompted me to respond with a message asking her if she was a politician that wanted to change the subject!

Needless to say, my next truck will be from one of their competitors. Yes, the transmission was self-serviced, but I have done that on each of my 6 trucks that I have owned and have never experienced this. If you can get someone at GM to at least try to address this, I'd sure appreciate it.