Trans clunking in reverse; help!

[TheV6Bird]

Hey guys,

My 95 3.4 A4 trans has been acting up. It drives fine, but while in reverse it will sometimes make a knocking noise, like it is hitting the car. Not like a loud bang, but audible. This happens only in reverse.

Driving the car normally, over a large bump I will hear some clunking. It doesn't really affect driveability, but I want to get this fixed.

I was thinking maybe the transmission mount, but after doing a search and reading some people have pointed to the U-joints as a culprit. The car has 110K on it. How hard is it to replace U-joints? I hear you need to bring them to a machine shop to have them pressed in. If it is the trans mount, I'm not sure whether to go with a stock GM mount, or go 1LE or poly. I only AutoX occasionally, and I don't have many power mods on my car. How much does the GM stock mount cost?

thanks guys [img]smile.gif[/img]

[C.O.Jones]

I would only look to the u-joints if the clunking noise happens right after you put it in reverse. I have a bad set on my aluminum driveshaft.

If it's a stocker, then you'll probably need to take it to a machine shop to have the old ones pressed OUT. They force nylon in around the rings and it is a huge pain in the *** to break that.

[95Batmobile]

I think your transmission declunkifier must have went out.

If that isn't the problem, you might as well get a 1-piece steel or aluminum DS while you replace those u-joints [img]smile.gif[/img]

[TheV6Bird]

Originally posted by C.O.Jones:
I would only look to the u-joints if the clunking noise happens right after you put it in reverse. I have a bad set on my aluminum driveshaft.

If it's a stocker, then you'll probably need to take it to a machine shop to have the old ones pressed OUT. They force nylon in around the rings and it is a huge pain in the *** to break that.

The clunking only happens sometimes when I press the gas to accelerate in reverse; never clunks after I put it in reverse.

Yeouch, I hope its not the U-joints because I want this to be something I can do myself.

[Dojo2000]

I was getting a clunking sound at low speed, especially in reverse. Turned out to be the exhaust hitting the brace under the car.

[TheV6Bird]

Originally posted by Dojo2000:
I was getting a clunking sound at low speed, especially in reverse. Turned out to be the exhaust hitting the brace under the car.

Hmmmm....I'll be sure to check that out too.

How can I tell if my U-joints are bad? Will I be able to move them with my hand? Leaking some sort of fluid?

[hockeyman]

Originally posted by TheV6Bird:
How can I tell if my U-joints are bad? Will I be able to move them with my hand? Leaking some sort of fluid?

Lift the rear of the car and jackstand it. Put the Trans in neutral, then grab the driveshaft and try to move it and turn it in any direction. If you see any sort of play (looseness) in/around the u-joints, replace the u-joints immediately!

[TheV6Bird]

UPDATE

Alright I put the car up on stands today to see what I could find. First, the U-joints have no play in them...I couldn't move them around at all, so they seem to be OK. I checked the trans mount...there seems to be a few very small cracks in some of the top areas, but not enough to really make it move.

BAD NEWS: I lifted up the whole rear end, started the car, put it in reverse with the wheels in the air (yes I put chocks around the front wheels so the car wouldn't move [img]tongue.gif[/img] ) and looked for anything hitting the car...didn't seem to find any, but when I put the car back in park with the wheels up there was this horrible chattering/grinding noise that came from the trans!!! However, when I put the car down and put the trans in park with the wheels on the ground, it did not make this noise at all...what the hell could that noise have been with the wheels up?

Bottom line: U-joints seem fine, but there is still a clunking noise in general, and a louder noise with the car in reverse. I think I'll just give up and take it to the shop.

[Dojo2000]

I'll just say that it was pretty stupid to start the car, not to mention putting it in gear, with it up on jackstands.

Did you make sure the wheels stopped moving before you put it back into Park? That could account for the noise.

[TheV6Bird]

UPDATE!!

As for the clunking noise from the trans....its not the trans. In fact, it is the exhaust hitting the tunnel brace. I found this out by putting the car on Rhyno ramps and putting the car in reverse while looking for the source of the sound. Looks like its not the U-joints or trans after all. Thanks everyone!

Oh, and in this time and the previous time, someone else was in the car while I was under it pressing the brake making sure nothing bad would happen [img]smile.gif[/img]

[Die Ford V8]

hmmmmm. i think i have the same problem, i will do what you did with exhaust and see what happens.

[Perry]

Hmmm...I was going to say that you are all wrong, but it must be an A4 not an M5. In the M5, it is supposed to do that, it won't though if you put it in another gear before you put it in reverse. Ideally the 5th to reverse is the easiest.