Have a hard shift from First to Second that gets worse with more power. All the other shifts work fine. Tried Lucas transmision additive but it made no change. Any ideas? Thanks

Is it auto or manual. It may be the synchro's. I had a 93 talon manual that had bad synchro's into 2nd all I had to do was shift to match RPMs with trans speed. It works no more hard shifts but I had to get used to it. It beats the alternative of getting another trans or getting that one rebuilt.

This is from a previous post. Not sure why it's just 96-00. I
thought 95 was same tranny without the electronics. My 97
needed trans rebuilt when I bought it and noticed the really
harsh 1-2 shift after warmup and would go away when I turned
the truck off until it warmed again. A few people said they had
luck with bore kits for the valve body. My trans & TC were fried.
Good Luck
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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.

Yeh mine has a real bad 1-2 when warm and sometimes even bucks 2-3. my remedy is to always start out from a stop in 2nd gear when the problem is present. My long term plan is to let it blow apart or what ever it's gonna do and then just get a 4L80E.