Transaxle noise question

[widebody911]

I'm trying to figure out if the noise coming from my trans is 'normal'

A few weeks ago, I removed the sound insulation from the back seat area. Of course now I could hear more trans noise, but that's expected. Then I did a day at the track, and it seemed to get louder. I put some sound deadening back in, and some lightweight carpet, which knocked the sound down a bit, but after 2 more track days, it's definitely louder than before.

The noise is hard to describe, but I'll try.

The higher the gear, the louder the sound. It's more apparent during the first instant of throttle transitions, ie on the gas or off the gas. It's a combination of a whine and a chatter. If I hold the throttle in one place, particularly in 4th or 5th, it will make a chatter of several cycles per second.

In lower gears, I get a loud growl out of the trans, which turns into the chattery whine in the higher gears.

It still shifts great, even after an hour or so on the track - the combo of SWEPOO 212 and the trans cooler seems to be working.

I had the trans rebuilt about a year and a half ago, and replaced the R&P at that time because of serious galling.

I change the trans fluid every other track day. I've been getting light amounts of fuzz on the drain plug, but no chunks.

My suspicion is that I'm losing a bearing . If so, I wonder how much longer I can drive it like this, and what the con$equence$ are.

Ideas? Questions? Derisive comments?

[Superman]

According to my understanding, bearing failures in transmissions do whine. The rhythmicness (I think I just invented a word) suggests wheel bearing to me. There might be two separate problems.

[wevoid]

Thom,

When your trans was rebuilt, were any bearings replaced, or just reassembled with the original bearings?

Have you inspected your CV joints? The increse in frequency with speed and higher gears sounds more like a road speed associated problem than a engine speed issue. This would lead me to drive shafts or final drive, which still includes lots of options....

Was the replacement CWP new or used?

If the issue is in the CV's, the $-v-risk factor is quite a bit lower than if the problem is inside the trans. But I am sure you would guess that.

More info and the board will home in on it I am sure.

Regards

Hayden

[widebody911]

CV's were replaced about a year ago. Rear wheel bearings about the same time.

Some bearings were replaced when the trans was done, but I will have to dig out the receipt to find which ones.

Any tests to narrow things down?

[Langers]

Have you thought about getting the tranny oil analysed? Should give you some idea as to what is causing the metal fuzz.

[red-beard]

Is this a 915?

Me thinks bearing. Replace now and you will not have to replace the shaft...

[wevoid]

Thom,

If CV's were new recently, that is less likely. Wheel bearings would not be noisy unless cornering. (at their first signs of failure)
If it is road speed related, that limits the likely failures to the differential carrier bearings and the bearings on the pinion shaft. Thats still a total of 8 bearings....
You can test the differential carrier bearings fairly easy. there should be no radial or axial movement of the diff. Use levers across the drive flanges to establish if the diff is moving at all.
Removing the side cover from the final drive will allow you to remove the diff and inspect the CWP, pus check if the pinion head has any radial or axial movement, that pinion shaft thrust and roller bearing package is the heart of the 915.
I suggest you investigate soon, the liklihood of catastrophic failure is high when a transmission has an internal noise, peripheral damage could take out quite a few other parts that are currently still serviceable

Regards

Hayden