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YOUR RESEARCHNoisy C4 transmission? (noob question)
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Replace fluid
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Performed · outcome unconfirmed · Original poster
The car was PPIed by a dealer in Texas and my indie mechanic has changed the fluid.
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Suspected cause · Original poster
Therefore, I am reasonably sure that it is not the R&P or CVs and therefore, likely a bearing.
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I just acquired a higher mileage (84K miles) 1999 C4.
The transmission seems quite noisy - especially under load at higher speeds. Specifically, a whine appears when accelerating at higher speeds (55 to 75 mph).
The car was PPIed by a dealer in Texas and my indie mechanic has changed the fluid. Neither remarked anything untoward. I also drove another high mileage C4 yesterday and it exhibited the same characteristics.
Is this normal behaviour for a C4 transmission?
Thanks
Fergus,
No this is not a normal thing unless you consider the fact that a gearbox that is not maintained normal.
After 84K it is probably time to have it serviced. The whining could be one of a couple of things. It could be a worn out ring and pinion, which would cause that whine you are talking about in all gears, or it could simply be an issue with a bearing that is starting to go. Either way it is time to get it taken care of. I would not expect changing the fluid to rectify the situation. Sometimes it does mask it a bit so that it is not as annoying, but sooner or later you are going to need to get it truly addressed.
I would be happy to discuss your options with you in more detail if you would like, gearboxes are what we specialize in. Either way, I hope that this information has been helpful.
Warmest Regards,
Erik Johnson
GBox Sales Manager
[phone removed] work
[phone removed] cell
www.gboxweb.com
Oh one other thing about this, should you decide that you can live with the whine, consider that if you break the ring and pinion, or a bearing internal does happen to fail, your cost of repair is likely to be much higher.
Erik, is there a driveshaft carrier bearing or anything supporting the viscus clutch?
FWIW, I have a C4 with 145,000 miles on the drive train, and I've never noticed or thought that it had any excessive wear - so, Fergus, I'd think the sound yours is making isn't normal.
Can you pinpoint what end of the car the sound is coming from? Does it happen in different gears at the same speed? If it does, could it be a CV joint or wheel bearings?
Erik, can an analysis of the tranny fluid give you indications of R&P condition? In general I've understood Porsche transaxles to have pretty robust ring and pinion gears - although they have other weaknesses.
There has been a slew of people with this problem recently, what the hell's going on?
Oh, I know, sealed bearings in the transmission.
We need to send a letter to Porsche concerning this.
Dear Porsche,
We don't know why you love sealed bearings so much, but please stop.
Love,
Rennlist.
Over 70 kph (42 mph), in fourth gear or higher, mostly under acceleration. It is most evident in 5th gear at 60 to 75 mph. If you lift off the accelerator, it diminishes to almost nothing. If you engage the clutch, it disappears. Therefore, I am reasonably sure that it is not the R&P or CVs and therefore, likely a bearing.
I have now heard from several people with the same issue on a variety of models C4 and C4S who report a similar situation. Many have had it for a long time...
My 1999 C2 Cab is also exhibiting this gear whining noise. Only mines starts in 3rd gear and like yours is only under accelleration. If I let off the gas and just "maintain speed", the noise disappears. I haven't had the car that long... so I have no idea what is considered "normal noises" yet. But it's my unofficial opinion that the main shaft and/or pinion shaft bearings are shot. I am wondering if "as it gets worse" it appears in lower and lower gears. Since the more the bearing is worn, the more the gear shaft moves from where it's supposed to be in relation to the other gear shaft. This would mean that mine is worse off than the original posters. I'm letting my local indy shop drive it this week to give his opinion. So we'll see. My C2 has 98k on it by the way.
Can someone please post a link to a sound file so we can hear what this "whining" sounds like? As if there aren't things to proactively worry about on these high mileage 996's - I am quickly developing worried grandmother syndrome!
What does a normal trasmission sound like?
What does one sound like with a failing pinion bearing?
Thank you,
