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Who's the gearbox Guru, a reason for noises.


4 Oct 2010
I pulled my gearbox off yesterday to change the clutch release bearing as it made a rattling noise when the clutch wasn't depressed, goes quiet when I dip the clutch pedal. After lots of blood and sweat its all back together but the rattling noise hasn't cleared although the new release bearing does seem to of cleared some of the noise. The Warranty ran out on it over the weekend I just realised, should of checked the date earlier, :x

By listening I traced the noise to the gearbox housing itself, so I'm wondering what part of the box would go quiet when the clutch is depressed?

Could it be the oil change??
Another part of the mystery is the noise wasn't really there until I changed the gearbox oil a few K miles a go, I've used the correct type 2.5L Motul 75w90 Synthetic but I wonder what oil was previously in there to make it quieter? It does get quieter when its warmed up.
It was a reconditioned box 2 years ago and I wonder if they used a different thicker grade? Wish I'd left the original oil in.

It runs through all the gear without a problem still.
Any idea's or if I should try another oil, or is it f**ked? :what:
I would wonder if it could be related to the DMF. Particularly at idle the two parts of that could be moving relative to each other and could make noises, it is usually the release bearing but you have obviously removed the possibility of it being that.
Does it only rattle at idle, or does it continue under load at higher speeds as well?

The clutch and DMF were new 17k miles ago, I don't think the release bearing was changed at the same time, which is why I suspected it. The noise is coming from the box part where all the gears are rather than the bell-housing so I discounted the flywheel although are you thinking it could cause an imbalance through to the gears at idle. There is not any vibration going through the gears or car.
There is only one guy I would recommend you speak to - Mike at Sports & Classics. Not only is he an expert in all things Porsche, he is an absolute expert on gearbox issues. Put your mind at rest and let Mike take a look. Even the trade send him customer gearboxes to repair and clients ship him gearboxes from abroad to repair. Why? Cos he knows what he is doing!
I eventually have an update of my Gearbox, after not having my gearbox for a month and having to buy another reconditioned one to keep me on the road, today I got my original Gearbox fitted back in the car along with a new clutch kit.

This was the issue, 1st main shaft was worn (or input shaft as was said) and 1 gear had lost a tooth.

Amazing so little wear causes so much noise and the cost of just this shaft was £930 :eek: and had to go on backorder from Germany.

I now have a spare reconditioned 996 3.6 gearbox for sale to recuperate some of my costs if anyone needs one.

You have had an expensive fix! Sorted one gearbox and bought another reconditioned one which is now surplus to requirement.

For anyone faced with gearbox isssues it is never easy - do I go for a recon box and not know what else it could be hiding, or do I have mine repaired properly by someone who knows what they are doing and I have the satisfaction of it being right after spending that much money or do I buy a replacement brand new gearbox from OPC?

The mainshaft was expensive! But as I 've always said, these cars ain't cheap to maintain - there are many people on this forum I bet that have had to spend on cars within the first year or two of ownership as various problems came to light possibly due to prior owners who likely ignored advisories on the basis that they are selling the car - so someone else inherits the bills. On the other hand, wear n tear is costly to fix.

At least you are now sorted. I wish you luck in finding a buyer for the surplus box.
Alpinaman. Its about 65k miles now, but I have just thrown a load of cash at it before I go on a few road trips this year and sorted a few other niggles out.

This whole gearbox experience has cost me about 4k but hopefully half (ish) of that will be covered by the sale of the now spare gearbox, it was reconditioned by a Porsche specialist and I have tested it for 900 miles before getting my original one back and it is a good box so hopefully with this in mind it should sell to someone that needs a known good gearbox. There are some used/untested gearboxes on ebay for 2.5k which is far too much.

You have had some seriously bad luck with that car considering its low mileage..

Good job that your extremely handy with the spanners.... :thumb:

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