Trying to diagnose a noise.
Thread Starter
11 Second Club
Joined: Feb 2005
Posts: 176
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From: Alton IL
Trying to diagnose a noise. Car, 99 Trans Am, A4 obviously. Fluid looks good.
To describe the sound, when I bought the car, I thought the ebrake was dragging. Sounds like a worn out brake pad. I get under the car, and spin, transmission in neutral, and start spinning the back wheels. After some close listening, unless its playing cricket voodoo mind games, its sounds like its coming from the tail of the transmission.
From what ive found:
Sound still happens if in Neutral and spinning the drive shaft by hand.
Sounds most noticable around 20-30mph. Could be less road noise and less exhaust noise at this speed, so im not sure.
Sound is MPH based.
Does not change if in 1st or 2nd, or 3rd.
Does not change depending on brake pressure.
Does not change if coasting or accelerating.
I went ahead and bought new Ujoints, figuring if I pull the driveshaft I might as well swap them out. If Its a transmission issue, ill just put up with it until I buy a new stall as well. Just bought the car last week, and its basically stock except for a K&N intake kit, and cat back exhaust.
I did notice oil build up around the rearend. But I havent bought new fluid yet, so im not sure on its level. I figured I wait and get new gaskets, and just drain and refill the rear end at the same time.
Thanks.
To describe the sound, when I bought the car, I thought the ebrake was dragging. Sounds like a worn out brake pad. I get under the car, and spin, transmission in neutral, and start spinning the back wheels. After some close listening, unless its playing cricket voodoo mind games, its sounds like its coming from the tail of the transmission.
From what ive found:
Sound still happens if in Neutral and spinning the drive shaft by hand.
Sounds most noticable around 20-30mph. Could be less road noise and less exhaust noise at this speed, so im not sure.
Sound is MPH based.
Does not change if in 1st or 2nd, or 3rd.
Does not change depending on brake pressure.
Does not change if coasting or accelerating.
I went ahead and bought new Ujoints, figuring if I pull the driveshaft I might as well swap them out. If Its a transmission issue, ill just put up with it until I buy a new stall as well. Just bought the car last week, and its basically stock except for a K&N intake kit, and cat back exhaust.
I did notice oil build up around the rearend. But I havent bought new fluid yet, so im not sure on its level. I figured I wait and get new gaskets, and just drain and refill the rear end at the same time.
Thanks.
Thread Starter
11 Second Club
Joined: Feb 2005
Posts: 176
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From: Alton IL
slight update.
Before I took the time to swap Ujoints, I just swapped drive shafts with my buddy. And its still there. He also listened, and thinks its coming from the tail of the transmission when we spin the drive shaft by hand.
Before I took the time to swap Ujoints, I just swapped drive shafts with my buddy. And its still there. He also listened, and thinks its coming from the tail of the transmission when we spin the drive shaft by hand.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
It is difficult to diagnose noises from a description.
Since you seen to have eliminated the rear end and the u-joints, it could be the trans.
The rearmost item is the oil seal on the yoke. I have no idea if excessive grit in there could cause your noise; excessive grit probably would cause a leak.
Next is the rear case bushing for the output shaft. They do wear out.
How many miles are on your trans?
The rear case bushing can only be replaced during a full rebuild.
If you want to fiddle with it...
First remove the drive shaft.
Then remove the tail shaft; it is easy to remove, but it will leak a lot of ATF.
With the tail shaft off, you can examine the rear seal and easily replace it if needed.
You can test the side-to-side play of the output shaft. I have heard of it moving a half inch side-to-side when measured at the rear end; I suspect that much play indicates the rear bushing is well worn.
Is this the kind of info you are looking for?
Since you seen to have eliminated the rear end and the u-joints, it could be the trans.
The rearmost item is the oil seal on the yoke. I have no idea if excessive grit in there could cause your noise; excessive grit probably would cause a leak.
Next is the rear case bushing for the output shaft. They do wear out.
How many miles are on your trans?
The rear case bushing can only be replaced during a full rebuild.
If you want to fiddle with it...
First remove the drive shaft.
Then remove the tail shaft; it is easy to remove, but it will leak a lot of ATF.
With the tail shaft off, you can examine the rear seal and easily replace it if needed.
You can test the side-to-side play of the output shaft. I have heard of it moving a half inch side-to-side when measured at the rear end; I suspect that much play indicates the rear bushing is well worn.
Is this the kind of info you are looking for?
Thread Starter
11 Second Club
Joined: Feb 2005
Posts: 176
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From: Alton IL
Trans is stock as far as I am aware. I just bought the car. So 133k miles.
I have a buddy coming over thats more of a mechanic than I am here in a couple minutes. We plan to go over everything, spin both tires in the same direction, and so on. Im wondering if it is the rear end, BUT both tires need to be going forward to make the noise. It could be a different/normal sound that I just barley hear when Im under the car spinning the drive shaft.
To me, it REALLY sounds like the Ebrake is dragging, but so far I havent been able to reproduce the sound while on jack stands. But I havent spun both tires in the same direction yet. And Im going to check rear end fluid today as well.
I have a buddy coming over thats more of a mechanic than I am here in a couple minutes. We plan to go over everything, spin both tires in the same direction, and so on. Im wondering if it is the rear end, BUT both tires need to be going forward to make the noise. It could be a different/normal sound that I just barley hear when Im under the car spinning the drive shaft.
To me, it REALLY sounds like the Ebrake is dragging, but so far I havent been able to reproduce the sound while on jack stands. But I havent spun both tires in the same direction yet. And Im going to check rear end fluid today as well.
Thread Starter
11 Second Club
Joined: Feb 2005
Posts: 176
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From: Alton IL
Yea I swapped out the driveshaft yesterday, and the sound remained, so I knew at that point it wasnt the Ujoints.
Just worked on it for a couple hours with my buddy.
Long story short, its in the rearend. The little noise I can hear in the transmission is unnoticable when you really start to spin the back tire. Sound seems louder towards the end near the hubs. So with the amount of mileage on this rear end, im just debating on rebuilding it, or buying a cheap/good one, and use it for awhile until I plan to swap to a 12bolt anyway.
Just worked on it for a couple hours with my buddy.
Long story short, its in the rearend. The little noise I can hear in the transmission is unnoticable when you really start to spin the back tire. Sound seems louder towards the end near the hubs. So with the amount of mileage on this rear end, im just debating on rebuilding it, or buying a cheap/good one, and use it for awhile until I plan to swap to a 12bolt anyway.
