Hello and first question - Gearbox whine

[stanuk964996]

Hi all, sorry for the long first post! Not a completely new member but not a prominent poster - have lost my password and the reminder process seems to take me through an endless cycle of pain - so I have started afresh!

Quite active with the 964 groups as I have had a 964 for about 5 years and have very recently purchased a 996 c2, as the 964 has become RS'd and so is no longer ideal as a weekend car if I want to bring the wife and kids...

So far I am really enjoying the 996 experience. The chassis is wonderful and the car feels every inch a 911. I really think the 996 will end up going the same way the 964 has value wise. Maybe not quite as far due to the air cooled / water cooled debate, but certainly I think people will catch on soon!

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.

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.

Hoping it's not some sort of gearbox bearing issue but would appreciate any feedback from others? Have also posted on Rennlist but I know the 996 forum is more active here in the UK... Thanks for any pointers!

 

[cheshire911]

Gearbox whine can also be diff noise. Just try to narrow it down.

I think the fact that it changes with clutch in and out suggests gearbox rather than diff. but try to rule it out.

Changing gearbox oil is by far a less costly option, but wear is wear.
Car coming to 100k miles and it may be general wear that can only be fixed by a gearbox strip and rebuild.

Have you considered giving Mike at Sports & Classic a ring? he is a gearbox guru and very knowledgeable on these boxes. He may even be able to diagnose it by what you tell him over the phone.

 

[infrasilver]

If the noise disappears once the clutch is pressed, it could be the input shaft, mine did the same and I had to back order the part from Germany and it was about £900 plus fitting. I now have my input shaft and internals as spare as I had to change my whole gearbox last year due to the casing breaking.
I also did the same and changed gearbox oil but it made no effect.

What 996 do you have as there is a difference with the gearboxes between 3.4's and 3.6's?

 

[stanuk964996]

Thanks for the replies.

It is a 1998 3.4.

Sounds expensive! I imagine 'while you're in there' means you end up doing the clutch and IMS/RMS at the same time as well.... :sad:

 

[cheshire911]

It looks like its going to be an expensive repair if it is the sorts of things that Infrasilver has mentioned - and he has experience of gearbox issues.

Leaving aside the "while you're in there stuff" you can look up the Sports & Classic website where he lists some prices for gearbox work.
It is worth a phone call to Mike there. he may also comment that with that mileage there may be issues with the crown wheel and pinion bearing.

http://www.sportsandclassic.com/index.php?page=services_gearbox_rebuilds

Sorry to be the bearer of possible bad news.

 

[stanuk964996]

Thanks... I think!

It is booked into Jaz at the end of the month for a major service anyway so I will get their opinion on the gearbox noise and go from there I guess...