Worn Crown Wheel and Pinion Symptoms

[Paul Glasson]

Can someone describe the symptoms to identify if a crown wheel and pinion is going, if the box is still good for 20000+ km once the wear becomes noticeable,and if there is any adjustment to take up slack or it is a throw out and replace item.
Symptom I get that is staring to be noticeable but nothing serious now, is on running against compression,especially in 1,2,3 there is a gear meshing hum,which goes away when I accellerate in each gear. I would not describe it really as a whine, more a gear meshing hum. Shifting & everything else fine.
Car has 173000km, not driven that hard by previous owner and me with occasional autocross (every 3 month),has synthetic mobil oil in gearbox with scheduled oil changes done if Porsche agent did do the change.
From reading posts this would appear to be one of the weakest points of these cars.

[Mike C5.]

When mine went (at 175K miles) there was no noticeable warning signs in terms of sound or drive line slop. Perhaps a mechanic with a trained ear and butt might have noticed something but I doubt it. I honestly think the only way to really get a handle on it would be to remove the side cover, clean the R&P and inspect closely for any signs of cracking. If you clean them well (spray degreaser) you might even be able to get some flourescent penetrant in there (and a black light) to look for cracks. Another thing that can be done (but you'll need special tools and probably have to remove the trans) is to measure the backlash between the gears and the pinion pre-load (torque). If these are way out of spec, I would think it's just a matter of time.

[Paul Glasson]

Mike C5
I would not be able to do the job myself as I do not have the garage space (living in a townhouse not allowed to do major overhauls as well).
This is not a sudden noise that has developed, but has gradually got worse, so my guess is wear rather than a crack, but I have never worked on a gearbox internals other than a 50cc motorcycle.
Question is, is the backlash between gears and pinion preload something that can be taken up, or is this parts replacement, and if so what likely parts and where to buy, and cost? I either try to buy parts before and budget the whole repair, or sell the car as is, but that would break my heart as the body and engine are in good condition overall.

[..P]

Read the posts and just wanted to drop a note. I have a 84 with 168,000 miles on the odometer now, and it "had" gear noise but doesn't any more. I may have just masked the issue, but I used AMSOIL synthetic gear lube. At the time it was the Series 2000 product, but they don't sell that any more in favor of their new marketing scheme called "SEVERE GEAR". In any case, I'm sure anything from Amsoil is a good or great product.

When I put it in my transaxle, it quieted the box down a lot, and it made shifting much much better especially when cold. I figure the Mobil-1 gear lube is good, but it's not as highly rated with regard to GL ratings as Amsoil is. The GL rating is that measure of corrosion resistance to "yellow metals" when the lubricant gets hot and reacts with sulfur. Generally, Amsoil is the "gold standard" when it comes to synthetic products. I noticed they have a 75W90 and I believe a 80W140. I figure if you wanted a bit more substance, you could toss in a 50/50 mix between the two, or just move up to the thicker product.

all the best, good luck,

P

[Mike C5.]

Paul, unfortunately parts replacement is really not feasible unless you have some special tools, an oven (to heat up the aluminum case to remove and install bearing races), etc. It wouldn't hurt to put in a sythetic lube as suggested above but ultimately, there's nothing more you can do other than avoid drag racing-type starts. The ring & pinion gear set alone costs around $500. Most people source a good used transaxle when the time comes. They are readily available since large numbers of 944 were built between 83 and 87. Good luck.

[nathan944]

used trannys are literally a dime a dozen. Just find a decent used one (200$-250) and run it till it breaks then replace again.

[Paul Glasson]

Thanks for the replies guys,
Gearbox replacement- here I do not know about spares availability. Will phone the only scrapyard that I know keeps Porsches. About 1 year back I had a gearbox rebuilding shop give me an approximate quote to redo my box when misdiagnosing broken clutch rubber, and they said about $800-$900 and that would have to carry a Guarantee. I am too frightened to ask the agent as it was about that just for the clutch plate replacement. In the mean time must try to get some AMSOIL if available here and perhaps drive the car until gearbox self destructs.

[Mike C5.]

You need to find out what specific parts get replaced. That price sounds like it doesn't include a new ring & pinion.