Drive shaft or tranny?

bae007 · #1 09-20-2005, 11:33 AM

1989 Crown Vic LTD, Ok so when I am starting off, if I hit the gas to hard the the car shudders or vibrates and I don't get start off power. After it shifts into second gear I can give it as much gas as I want to and the car responds accordingly. If I start of slow, not to much gas, no vibration/shudder. This only happens when starting off. The car has only 65K so I don't think it is the tranny what else could be causing this. If it is the tranny whats wrong.?

Mines69Olds · #2 09-20-2005, 12:04 PM

Get under the car and grab the driveshaft and try to turn it back and forth. It shouldn't turn at all but if it does you might have a bad U-joint.

fbi-interceptor · #3 09-20-2005, 05:03 PM

i would have a tranny tuneup.... new fluid, gasket and filter.... then i would change your rear end gear fluid

theman100 · #4 09-20-2005, 05:46 PM

sounds like you have a driveshaft angle problem from your concern.
but, does it feel like an engine miss?can you feel it if you power brake it?
do you have any vibration at highway speeds? need more info to help

bae007 · #5 09-20-2005, 07:08 PM

Quote:

Originally Posted by theman100

sounds like you have a driveshaft angle problem from your concern.
but, does it feel like an engine miss?can you feel it if you power brake it?
do you have any vibration at highway speeds? need more info to help

No vibration at highway speeds. If I am going under about thirty miles per hour and punch the gas the car vibrates/shudders surges, I know its not engine related it has something to do with the tranny or driveshaft. When I tried to powerbrake it just now the wheels didn't spin but the motor reved up so I know its not the motor, and I didn't feel any vibration/shudder, the wheels just didn't spin, I am just not getting the transfer from the motor to the wheels. After about 30 mph I can punch it and the car will take off. from starting position to around 25-30 mph I have to take it kinda easy or else I get the problem I am describing.

ModMech · #6 09-20-2005, 07:57 PM

Your car has an "AOD" model trans, and this is THE failure mode of choice for the torque converter. The harder you try to accelerate, the harder it shakes.

Time for a new TC. No, you CANNOT "fix" it.

theman100 · #7 09-21-2005, 08:57 AM

the torque converter does not lock up during hard accel,if it was the the torque conv. when it would lock up then it would shudder, to diag this just hit your brakes and the brake on/off switch is monitered by the pcm and will not let the conv. lock up because the pcm see's that you are stopping.if the conv. locked up at a stop the engine would die.
check to see if the tailshaft bushing in the trans is worn, see how much movement you have where your slip yoke goes into the trans. there is bushing that your slip yoke rides on. did you check drive shaft angles?

ModMech · #8 09-22-2005, 09:20 PM

Quote:

Originally Posted by theman100

the torque converter does not lock up during hard accel,if it was the the torque conv. when it would lock up then it would shudder, to diag this just hit your brakes and the brake on/off switch is monitered by the pcm and will not let the conv. lock up because the pcm see's that you are stopping.if the conv. locked up at a stop the engine would die.

You clearly do not understand that the AOD lock-up Tc is NOT PCM controlled.

The failure mode of the AOD lock-up TC is EXACTLY as I described, and it is NOT the same as for the AODE/4R70W.

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