84 Euro

I am wondering if anyone can glean anything from the soundbytes below. While on stands I ran it through the gears, wheels off and then with wheels on. The gear whine is very noticeable, as well as what I think are some unhealthy noises - clunking and rattling - coming from the gearbox.

When wheels off, no noticeable "rattle" while idling in 5th gear, but a distinct series of rattles/clunks when coming off a throttle blip. Thinking gearl lash, but seemes excessive to me.



When wheels on, idling in 5th gear, there is a distinct and constant series of rattles - almost like marbles in there.



Any thoughts?

PS - this box was recently apart for synchros, and have been chasing a vibration ever since - gearbox seems to be the only suspect left.

 

CV Joints could give you the clunking and 'marbles' noise ... have you eliminated them yet?

Use a mechanics stethoscope, or large screwdriver to your ear, to narrow down where each noise is predominantly coming from. It's possible that what you think may be the gearbox, is in fact conduction of a noise from somewhere else.

However ... it's not unusual to hear a bit of clunking and whining on a gearbox that's free running, with only the inertia of the wheels and other driveline components to load the gearbox and diff. How does it drive?

Edit: Just listened again ... it sounds a lot like clunky CV or bearing.

 

Thanks Dave. Yes, the next step is to unbolt the axles from the gearbox and run it to isolate the noise.

Back story:

Gearbox was removed last winter for new 2nd and 3rd synchros. TT was rebuilt by Constantine. One halfshaft was replaced because of an obvious wobble. Upon reassembly, an engine RPM dependant vibration/drone presented itself (in any gear, same RPM intervals), seemingly coming from the rear of the car. We have been through everything numerous times looking for potential contact (new MM last year, tranny mounts good, exhaust clear, clutch/flywheel balanced, , new release and pilot bearings, etc.). In my opinion, the only unknowns at this point are the one remaining halfshaft/CV joints, rear wheel bearings (which *seem* fine), or gearbox itself.

I should add that the whine is present driving down the road, most noticeable in higher gears - this was not present before the synchro work.

I won't be back on it for a couple of weeks. In the meantime, any insights as to what could have gone wrong duriing the synchro replacement to cause a "rattle/knocking" and what I think it excessive gear whine in the gearbox (assuming we isolate the noise to the gearbox) is appreciated.

 

Seems basic, but have you verified that the gearbox is filled correctly?

I only ask because of the following story:

A customer brought us a 1992 Saab 900 automatic. He was complaining of a whining noise, particularly at speed. The transaxle assembly had been replaced at the local dealer after a quick-lube place had drained the differential instead of the engine oil (common on classic 900s as the transmission case is the oil sump). The dealer that installed the replacement transaxle assembly forgot to fill the differential, and of course this lead to pinion bearings whining not long thereafter.

 

Yes it is. My first thought as well - checked and verified full before I made the recordings. Thanks for the thought - sometimes the basics do escape us.

 

Update - noises were still present after disconnecting the axle halfshafts, and the backlash seemd excessive with a definitive matallic clunk as the backlash was taken up (much moreso than on other 928s we checked).

So, we pulled the transaxle. The gear oil (with only 200 miles on it) was full of metal particulates and the drain plug was quite furry.

Also, it appears that one of the axle carrier shims was pinched upon previous reassembly, possibly causing an issue with bearing preload and/or R&P backalsh.

It has been packed up and sent to Greg Brown for diagnosis and repair. More later.

 

Hi Brian,

Sorry to hear about the news with your tranny, but at least you are on the way to finally getting it done.

Can't wait to hear about a successful conclusion and smooth first ride after getting everything back together!

Cheers,

 

Thanks Constantine. Between this, and the failed head gasket the year before, it has been a long road.

 

Transmission is back in the car and performing like new - better than I thought it could. Greg found much wrong inside, some due to years of a poorly performing clutch, but mostly issues arrising from 2 previously "attempted" rebuilds that failed miserably.

Hats off to Greg for another fine 5-speed rebuild - it has truly transformed the car.

Now to solve my other issues....

 

Glad you guys got it installed.

Your transmission was very interesting to rebuild. Pretty hard to comprehend.

I've never seen a transmission that had more pieces in the wrong place or missing than that one.

I think Ray Charles, with Stevie Wonder reading him the Workshop Manual, could have done a better job.

 

I too have a Greg Brown blessed 5 spdtrans and it is AWESOME !! Shifts far better than I even knew it could.