Still clunking

[85LincolnTC]

I dont know if anyone remembers me, I havent posted here much. Anywho, I have a 91 gm that i bought back in febuary. Its had a few issues but overall its been great. There are a couple things that have been bothering me though. One of them is when im driving the car, and it shifts from 3rd to OD there is a clunking sound, i can feel it too. Also does it when downshifting, and i can hear it if i shift from reverse to drive while sitting still. Feels like it is coming from the rear end maybe? Is there a bushing on the rear end that commonly goes bad? Ive had a lot of RWD vehicles and have never experienced this. The car has somewhere around 170k miles. (the odometer does not work, but there was an oil change sticker under the hood from november of last year that said 148k. So im just estimating

Thanks in advance

[miamibob]

Sounds like it could be Torque Convertor Shudder - common in AOD tranys. LUBEGARD makes a product that is helpful. Remember a certain "kick in the pants" jolt is normal in these units. Bobby

[sly]

AOD doesn't have the shudder issue, that's the AODE/4R7# transmissions with the clutch lockup.

with the door open and the car running, hold the brake and shift it from R to D and back a few times. If you hear the same clunking... it's probably u-joints. The AOD should shift firmly into OD when it's working right and the transmission itself will make it sound like a clunk, but if the stationary tests (and from your post, I gather it does fail this test) make the noise, it's probably the u-joints.

[miamibob]

AOD doesn't have the shudder issue, that's the AODE/4R7# transmissions with the clutch lockup.

with the door open and the car running, hold the brake and shift it from R to D and back a few times. If you hear the same clunking... it's probably u-joints. The AOD should shift firmly into OD when it's working right and the transmission itself will make it sound like a clunk, but if the stationary tests (and from your post, I gather it does fail this test) make the noise, it's probably the u-joints.

Right! I was thinking of my Dad's '93 GM that was an AODE!!

[gadget73]

A clunk on a 3-4 shift in the AOD is very common. Bad U joints or a bad transmission mount will make it feel a lot worse though.

[85LincolnTC]

I don't believe that its the transmission itself making the noise, though i could be wrong. When sitting still, holding the brake, and shifting from D to R i can hear the same noise. Is there a way to check if its bad u joints? I have gotten underneath the car before and shook the drive shaft, but didn't hear anything.

[sly]

if you get under it and can shake the drive shaft, the u-joints are shot. You should only be able to move it slowly rotationally. There should be no wiggle to any of that. There should be some slight play that allows you to move the shaft back and forth due to the slack in the gears, but that's it.

[85LincolnTC]

If i get time tomorrow i'll get underneath and try again. So basically i should have absolutely no play in the drive shaft? other than it moving a little in and out of the trans? And if they ARE bad, i should be able to move the shaft with just my hands?

[sly]

you should be able to rotate the shaft back and forth about a degree or two, but it should not have any side to side motion. there should be NO play in the u-joints If you can see any of the 4 bearing caps looking like they wiggle when you move the shaft, it's bad. and yes, all this with just hands. If the transmission's tail housing is resting on the crossmember... the transmission mount is bad and the clunking could just be the housing banging the crossmember.

[pantera77]

My 91 wagon clunks like a bitch. U joints are tight and the trans mount is decent. I just chalked it up as to being a worn out 21 year old car.

And all 5 of my AOD equipped cars have had the typical 3-4 clunk.

[sly]

my 3-4 I would call a mule kick style shift in the 88... kinda a mild kick in the pants in the Mark. But that's both with shift kits. When the 88 was stock... you couldn't feel the shifts at all unless you were WOT and then it was more slip shifts (old stock sloppy shift). But when my u-joints went on the 88... you could hear the clunk when shifting from R to D and at most shift points, especially OD.

They're not that bad to change either... getting the socket to get the damn bolts off the spider on the rear diff however can be an operation in frustration. Thankfully I've got a mechanic buddy down here that has that M12 12-point impact socket.

[gadget73]

mine feels like I ran something over if I side-step the pedal about 50, forcing a 3-4 shift. The original trans banged and thumped severely but I found the crossmember was rotted out at one end and it was smacking the floorpan when it shifted. The mount was also more like jello than rubber. Actually the current mount is very jello-like as well. Finally got the leak fixed, never did change the trans mount.

[85LincolnTC]

I didn't get a chance to get under the car today. I may wait until i can borrow a jack from someone, because all I have is the factory bumper jack and I really don't like getting under the car with only that holding it up. This may just sound like laziness, but couldn't I just swap in another driveshaft? It would cost me the same as getting new u joints.

[sly]

then you'd have to deal with the unknown status of the used driveshaft's components. You don't know how long the u-joints would hold on that one. Yes, technically you could do that if you can get one from another TC.

and no worries about delays. +1 on safely getting under the car with jackstands.

[Piece-it pete]

Every AOD I've ever owned felt like it was failing (and didn't). I call it the Ford thunk. Putt, putt putt putt puttputtputtputt - (thunk! shimmy) - Putt, putt, putt, putt

Changing U joints isn't hard - where you be man?

Pete