2003 GMC Sierra - shifting problem

COP TZR · November 21, 2006

2003 GMC Sierra 1500, 5.3L, auto, 4wd - freshly complete and upgraded transmission and transfer case

1) last year - revving between 2nd and 3rd gear when accelerating COLD, revving when turning 90deg. corner at 20-30mph, when warm shifts perfect

2) 2 weeks ago - revved between 2nd-3rd, upshifted, then downshifted, revved to the limiter and shortly after ( 20km) lost OD, than shortly (10km) lost 3rd, transmission fluid blowing out rear vent hose

3) today - $2500 rebuilt and upgraded transmission, was rough idle when shifting between gears and even stalling, most of that is gone after several very short drives around block and transmission warmed up

Problem - transmission still revs between 2nd-3rd when cold, give it 5 minutes, shifts good, but will do it very odd time. Turn TOW MODE "on" and try it COLD, transmission shifts good

Thoughts

GM programming problem

"The automatic transmission slipped alarmingly when shifting from 2nd to 3rd and the truck seemed to lurch when accelerating moderately after making a right turn. The dealer reprogrammed the truck's computer with new codes issued on a GM Service Bulletin"

Rebuilt transmission and throttle position not relearned itself

"There is a GM bulliten that was issued for this complaint,it usually happened after a trans repair or replacement a few things can cause this problem but ill outline what the GM document says,it is up to you whether to attempt this yourself or have the dealer do it for you,ill give you the Doc number so you can present it to the dealership so they can refer to it,the GM doc number is 1351952.What may be happening is that the throttle position sensor was not relearned and causing the downshift and delayed shift to 4th"

PLEASE HELP, have no $$$ left and need this truck, last resort is to buy programmer and increase shift points to bypass this problem.

THNX in advance.

GM-Tech · November 21, 2006

That document number you provided is for MEDIUM duty trucks with an Aisin (Japanese) transmission. Therefore, this doesn't even come close to applying to your vehicle. Never even heard of relearning a TPS. Must be something on those specific trucks.

I'm not a tranny guy and don't know what's wrong, but if you spent $2500 on repairs to fix this and it is not fixed, I'd be driving back to that place and let them figure it out.

Here's the header of that document so you can see for yourself...

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Subject: Harsh Shifting, Delayed Upshifts with Possible CHECK TRANS Lamp Illuminated, Possible DTC 21 Set (Perform TPS Relearn Procedure) #02-07-30-025B - (06/27/2003)

Models: 1999-2004 Chevrolet W-Series Medium Duty Tilt Cab Models

1999-2004 GMC W-Series Medium Duty Tilt Cab Models

1999-2004 Isuzu NPR/NQR Commercial Medium Duty Models

with 4HE1 Diesel Engine and Aisin Automatic Transmission

COP TZR · November 21, 2006

That makes sense, the idea of the computer causing the problem was what the thought was...thnx for the research...going to dealer in 2 days for "major vacuum error" thought maybe they may need to service/upgrade program to help transmission problem. I was told the vacuum problem should not affect the transmission in any way, going to fix, just to see.