4T60E Transmission erratic operation in Drive only

[Student]

1992 Park Avenue with the m13 or 4T60E transmission with the PRDdl in D. As the car went above 80 kph, the car felt as if the brakes had been applied strongly. The manual indicates this as a "Tie-up", two opposing clutches are engaging at the same time.

Also a vibration occurs while in D if anything other than light accerlation to 80kph when the tie-up occures.

If I put the PRNDdL in d, the car operates normally. No matter how hard acclerated.

If I unplug the transmission electronic control, and shift manually, the transmission vibrates, and is not drivable.

Any help out there?

Mark

[public]

I believe your "Tie-up" diagnosis may be right on. It sounds like 3rd gear is not disengaging on the upshift. I am not certified on transmissions so I cannot advise on a repair. Most of my transmission repairs are the same two things. 1 fluid and filter. 2 a new modulator. Both cheap but I dont think either will help here. Good Luck.

[-Josh-]

I'll check for bulletins on it at work.