993 turbo gearbox noise...
Discussion
My 993 turbo had a feint whistle in 5th and 6th from about 2700rpm and up. Gearbox has been rebuilt now - new bearings throughout, new synchs and new 5th and 6th gear sets. In fact we've now tried three different, new, matched 5th gear sets. It's still exactly the same. Whistle/whine in 5th and 6th.
The specialist is baffled, I'm baffled and Porsche are baffled.
Can anyone suggest a remedy or recommend a specialist who might be able to help?
I don't really want to throw any more cash at it until I've harvested as much advice as possible.
Thanks.
I'm getting desperate!
The specialist is baffled, I'm baffled and Porsche are baffled.
Can anyone suggest a remedy or recommend a specialist who might be able to help?
I don't really want to throw any more cash at it until I've harvested as much advice as possible.
Thanks.
I'm getting desperate!
Hi Gents,
All the bearings in the box, synchros on 1st, 2nd and third, and the gearsets for 5th and 6th have been replaced. All original Porsche parts. Also as mentioned before, we've tried three different, new, matched gearsets for fifth but all were noisy. New oil at each of the four rebuilds.
The only relevant part in the box left to change would seem to be the main shaft (which appears to be fine), but its an expensive option for the sake of troubleshooting.
I'm stumped and running out of money!
All the bearings in the box, synchros on 1st, 2nd and third, and the gearsets for 5th and 6th have been replaced. All original Porsche parts. Also as mentioned before, we've tried three different, new, matched gearsets for fifth but all were noisy. New oil at each of the four rebuilds.
The only relevant part in the box left to change would seem to be the main shaft (which appears to be fine), but its an expensive option for the sake of troubleshooting.
I'm stumped and running out of money!
Crown wheel and pinion?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Edited by ism123 on Saturday 8th October 21:38
Thank you gentlemen, I'm pursuing both leads.
Pre re-build oil was quite poor condition despite supposedly being changed 700 miles earlier by a main dealer. That would suggest an additive...
I'll investigate the crown wheel and pinion theory; was it just the output shaft bearings or the actual gears or both which were suspect?
Great tips - keep them coming!
I'll post back with any progress.
Pre re-build oil was quite poor condition despite supposedly being changed 700 miles earlier by a main dealer. That would suggest an additive...
I'll investigate the crown wheel and pinion theory; was it just the output shaft bearings or the actual gears or both which were suspect?
Great tips - keep them coming!
I'll post back with any progress.
I've been unlucky with front diffs - the first one went after the gearbox bearing mentioned above had been replaced. Crown wheel assembly bolts failed and wore the diff casing making it unrepairable.
Opted for new Porsche diff that failed last year 12k kms later as threadlocked nut on input shaft came undone and shagged the casng on the new diff.
Am now runnng on a recon diff supplied by my indie specialist who sympathises with me. He is the one who tells that the bearing on the gearbox output shaft is under-dimensioned. He puts my troubles down to having the extra torque of a 450bhp GT2 engine spec, and putting this through the 4wd system.
Either way, for the minimal cost that it represents, make sure that bearing is replaced. Yeah, and kiss it before they press it into the casing.......
:-)
Opted for new Porsche diff that failed last year 12k kms later as threadlocked nut on input shaft came undone and shagged the casng on the new diff.
Am now runnng on a recon diff supplied by my indie specialist who sympathises with me. He is the one who tells that the bearing on the gearbox output shaft is under-dimensioned. He puts my troubles down to having the extra torque of a 450bhp GT2 engine spec, and putting this through the 4wd system.
Either way, for the minimal cost that it represents, make sure that bearing is replaced. Yeah, and kiss it before they press it into the casing.......
:-)
Johnyc is your car also higher than standard turbo spec hp? How many miles has it done and have you had any other gearbox work carried out?
It was suggested to me by someone that careless or brutal messing about on a dyno can cause these symptoms too. I don't know what any previous owners may have done, but it's possible that it's been on a dyno in it's 15 years.
It was suggested to me by someone that careless or brutal messing about on a dyno can cause these symptoms too. I don't know what any previous owners may have done, but it's possible that it's been on a dyno in it's 15 years.
ThirstyMoose said:
Johnyc is your car also higher than standard turbo spec hp? How many miles has it done and have you had any other gearbox work carried out?
It was suggested to me by someone that careless or brutal messing about on a dyno can cause these symptoms too. I don't know what any previous owners may have done, but it's possible that it's been on a dyno in it's 15 years.
It's putting out 502 BHP and 603 NM Torque on 0.8 bar boost, has a carbon lined rear lsd (whatever that is), has been fairly extensively modified with hybrid K24.550 turbos etc. It has 115K miles and although the engine was completely rebuilt 7K ago, the gearbox has never been touched. The changes are very sharp with no baulking/ clonking or grinding even when cold. It has a quickshift system and a SACHS race clutch and flywheel set-up.It was suggested to me by someone that careless or brutal messing about on a dyno can cause these symptoms too. I don't know what any previous owners may have done, but it's possible that it's been on a dyno in it's 15 years.
It's always whined a bit in 5th and when I asked about it I was told they are very strong and not to worry about the noise, which I don't as it's just 5th.
Typically now I've said this it will disintegrate, it's the only thing that hasn't been rebuilt or replaced in the last 2 years!!!
Thanks a lot, I love it. I get it out all the time both on track and on runs with the Scottish Pistonheads crowd.
Have spent a small fortune on it, keeping it driving perfectly so hopefully the gearbox will be fine and if it only whines a bit for the rest of it's days I'll be quite happy
Have spent a small fortune on it, keeping it driving perfectly so hopefully the gearbox will be fine and if it only whines a bit for the rest of it's days I'll be quite happy
So the final outcome...
The specialist has now removed, stripped and rebuilt the gearbox 5 times with various new gearsets from porsche. New bearings throughout, new synchros etc and the noise is still there.
It drives beautifully and is faultless apart from the whine in 5th (which is new).
Mainshaft has been inspected and measured and found to be ok. Mystery.
My particular thanks to Northway who have definitely gone above and beyond. Several additional days labour and no extra charges. Highly recommend them.
The specialist has now removed, stripped and rebuilt the gearbox 5 times with various new gearsets from porsche. New bearings throughout, new synchros etc and the noise is still there.
It drives beautifully and is faultless apart from the whine in 5th (which is new).
Mainshaft has been inspected and measured and found to be ok. Mystery.
My particular thanks to Northway who have definitely gone above and beyond. Several additional days labour and no extra charges. Highly recommend them.
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