New 996 owner - gearbox whine??

New member of the watercooled club here in the UK and very happy with my purchase so far. Have had a 964 for about 5 years but she is steadily becoming more track focused and now with Recaro's, no rear seats, etc. so was looking for a comfort option...! I've just picked myself up an early 996 c2 manual. Arctic silver with Aerokit, GT3 wheels, M030 and LSD from factory, sport seats, etc. and she feels great. Very impressed with the chassis and it feels plenty quick enough too. However, I have noticed a slight gearbox whine. Only really noticeable in 3rd or 4th. Noise reduces but doesnt completely disappear if I depress the clutch and let it coast, and comes back when I re-engage the clutch. It's not really loud but is definitely there. I would say about the same volume as the engine noise or just below and once your ears are attuned to it, noticeable with the radio on at low volumes. I think the noise is less apparent in 5th or 6th, but that might also be because the road noise is too loud at this point. Hoping it's not some sort of gearbox bearing issue but would appreciate any feedback from others? Thanks.

I should add, it has 97K on the clock and I cannot find any record of the gearbox oil being replaced... I see the service interval is 96K for the gearbox oil, which the forums and logic would suggest is too long by about 3x. I have ordered some Motul Gear 300 LS 75W-90 to do a fluid change at the weekend as the box also feels quite notchy (especially compared to the 993 box I have in my 964), so am hoping this will improve things.

New gear oil should definitely "not make it worse". Give us an update afterwards.

You might also want to check the adjustment of the shift cables. Mine were out of alignment and ruined the feel of the shifter. You remove the lower center console and there is a $5 plastic alignment tool that one uses. Also, when I put a stiffener in my transmission mount, I started hearing Lots of noises from the transmission I had never heard before as the connection between the body and the transmission was allowing many more vibrations through. You may want to check your transmission mount especially with 97k on the clock. If the rubber has broken, you may be getting noise from that.

I hate to tell you this but it sounds like the same problem I have. A Pinion Bearing in the rear diff. The rear diff is located in the trans and the only way to repair it is to rebuild/put in a new transmission. Mine also has the same symptoms in 3rd and 4th. If you search the forums here there is a lot of information about it. Let me know if I can help out at all

You have nothing to lose by changing the fluid and replacing with Motul gear oil. Hope that works for you.

If there are silver flecks in the oil, the pinion bearing is starting to go.

There is a filthy test for seal failure of the 'sealed' bearings in the gearbox. Stick your finger in the drain hole and grope around for the magnet that should be there. Try to scoop off the sludge that has accumulated. That sludge is the grease that should be in the bearings.But the seals have failed,dumped the grease and it ends up at the bottom of the gearbox. Not good. The fix is new bearings and a few little other gizmos. The guru I use is Eric Johnson at Race Line in Colorado.[phone removed] phone.Helpful guy & knows the subject well.

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Rebuilding the differential is not a big deal. Had mine done for $1700.

Speak to Mike at Sports & Classic in south Manchester (near Knutsford)....

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Locally? That would have been awesome. I'm almost through the saga of sending mine over the border to the states. 75 cents on the dollar and 500 bucks shipping each way has doubled the quoted figure above for me. Unreal amount of paperwork and brokerage hassles. I could've flown it to denver as oversized luggage for less - or better yet, driven it down and skied a few days in the spring. I had the same issue the OP describes, and had the same sludge mentioned in the gearbox along with shavings. Fingers crossed when it gets back this week that it's good for another 170k kms. But I digress - OP, hopefully someone will point out a competent rebuilder in the UK for this sort of work. Personally I'd rather fix my own box than take a chance on a used one.

Sorry to hear about your problem with the diff. Yea, mine was rebuilt very recently here in Van (albeit it didn't solve the problem with my car - was a misdiagnosis). I can give you details if you want - PM

I think I have the exact same problem. The car shifts silky smooth, transmission fluid has been drained and refilled, but the trans sounds like a racing transmission. The sound only occurs when 'on the gas' (either accelerating or holding speed), and it's only speed-dependent - not RPM or gear dependent. When I let off the gas, the sound almost completely disappears. It sounds like a bearing problem to me - I was thinking with one of the half shaft bearings, but after reading this, the R&P bearing makes sense as well. What do you think? What should I do with it next? Think I can keep using it until winter, and then pull it apart and ship it out?

You're describing exactly the issue I had with mine. I couldn't stand to drive it, but GBOX told me it would have actually been safe enough to drive the car all the way to them to do the work. The pinion bearing that's wearing will be replaced anyway. Biggest issue is that the bearing is likely making some metal that won't be helping the rest of the trans. I should've recorded some sound. They'll be in there anyway, great time to upgrade the diff.

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Thanks! On the fence about an LSD though - the 996 is a cabriolet that is primarily driven by my wife. I don't think she would even notice the difference. I only drive it on rare occasions, such as PCA club drives or date nights. Several years ago, I took it out to Laguna Seca for two PCA DE events, and the handling and acceleration through the corkscrew were already amazing.