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GM tranny vibration

I drive a 1994 olds 88 with 3800 series 1 engine and 4 speed tranny w/lockup torque converter. The torque converter typically locks up at 75km/h or above once acceleration is down to a minimum (seems to be normal operation to me). The problem is is from 75km/h to about 85km/h (45-55mph) while the converter is locked the car shudders like the entire drivetrain is pulsating if there is any load on the engine (anything more than minimal throttle). Once the car gets up to about 85 it seems to "build up steam" and the shuddering smooths out and dissipates. If I accelerate EXTREMELY slowly from 75 to 85 minimizing engine load there is no pulsation, and if i accelerate hard (maybe half pedal or so?) it just kicks off the torque converter til i let back off the gas again after im out of the "pulsation zone". So far I have avoided this issue by simply staying either below

75km/h or at 85km/h or above, (which usually isnt a problem given most roads i drive on the traffic typically moves at either 70 or 90). Any ideas?
Reply to
Pessimism
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Reply to
Ken Hilson

How long has it been doing this???

Reply to
Joseph Fox

quite a while, i dont remember when it started, at least since last summer

Reply to
Pessimism

Gm had trouble with this one. The T.C. lockup valve in the valve body has worn its bore oversize,and the tc is slipping because of it. Correct repair is to replace valve body with updated design, but some people like the kit by transgo (I think that is the name).

Reply to
CURLY

Can you give me an idea of how much labour is involved in this? must the whole tranny be dropped or can it be done through the pan, and how much would this cost compared to a new transmission. also was wondering if the newer 4t65e trannies are drop in replacements for one liek this? i think its a 4t60 in there now

Reply to
Pessimism

Just a hunch, but I would check the basic stuff like mounts, cv joints ,tie rod/ rack ends and tire balance. It sounds to me you are discribing an out of balance condition that is not present when torque is applied. Grab your tires and jerk them left and right. Do you hear a knock? With the hood open, have an assistant put the car in drive and then reverse with the brakes on and note any engine movement. Jack up one front tire at a time and twist the cv joints back and forth with vise grips. Any slop means trouble.Look for cracked boots. I wouildn't dive into the trans without making sure all of that is right. An out of balance tire on worn steering parts can feel like the car is falling apart. Just my 2 cents, I am no expert.

Reply to
TOLYN9

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