Knocking sound - suspect tranny

[asian312]

Roughly a month ago I installed a new Shep 4-spider center diff. The car was bought in May and the previous center diff was eaten by the spider gears. I've babied the car around with a few high way runs and no launches. Well Sunday I took her down to the track and gave it a whirl. Launches from 3500 to 4000 rpm with an OEM clutch (is slipping, smells bad) and letting it slip off the line yeilded a best of a 2.1 60' time. Well as normal, I'm always paranoid after a track day and drive around town with the radio off to listen for things. I noticed a knocking (almost poping like) sound when giving her moderate throttle or letting off moderate acceleration. I'm pretty sure it's the tranny and sounds vaguly familiar to the sounds I was getting from my first center diff.

Here are the things I've been able to isolate:
- happens on moderate acceleration
- happens after letting off from accelerating
- can hear it while in gear and out of gear when coasting to a stop
- with and without brakes
- revs do not affect frequency of knock
- frequency changes with speed

I'm hoping that it's not my center diff again and maybe just a CV or something. Any ideas? I'm going to take out the diff tonight and pray for the best, but any input would be great.

 

[housegsx]

It could be a cv. Mine was clicking for a while, but now it has changed to a very slight 2 or 3 knocks/pops just when I slowly start to accelerate or stop.

 

[asian312]

Update:

Well I've got the car off of all fours and this is what I got:

- Passed center diff check - 1st gear spins all four tires
- If I let the clutch out quickly (not dumping it) the car jolts mildly as the transmission engages the wheels.
- If I spin the two front tires in the forward rotation with the tranny in neutral, there's a 1/4 to 1/2 turn between the time I start to turn and the time the tranny engages the rear wheels

So, is it the center diff? Missing teeth in the t-case?

I heard there is an ongoing recall on t-cases for the AWD. Any truth to this?

 

[asian312]

New update. Here's where it gets interesting:

Broke down the tranny and the center diff is A-ok. The shims are in excellant condition and the housing shows zero signs of wear. So where does this leave me now?

1) check drive shaft throughly - Other than manual inspection, are there more methods to check the U-joints? Where would I purchase a replacment u-joint pin and bushing?

2) check transfer case

 

[asian312]

Completly baffled at this point:

I've tore the tranny down to it's individual components and still no signs of missing or worn teeth on the gears. Only two oddities I've found through this is a possibly bad CV joint (needs to be repacked with grease) and I did not see the small ball bearing located on the shaft with leads to the transfercase and that the center diff resides on.

All in all, I'm replacing the seals and clutch while everything is off. Best thing I gained I suppose is piece of mind.


Lasts note...where can I pickup tranny seals? I spoke with John at Shepracing and he suggested the dealer is the easiest bet, but are there any other cheaper options.

 

[resilva]

Did you ever find out the exact cause of your problem??

What finally fixed it?

-Richard Silva-