Rebuild Gearbox...£££??

[jonk]

So, my lovely bargain 944 S2 goes brilliantly and feels tight as a drum with everything working and no warning lights etc... However, with 160k under her belt, the gearbox is most definitely noisy. I've lived with it for 3 months or so after purchase.
Changed oil to swepco, and no real difference so I think I'm going to have to bite the bullet and get the bearings done. Most noticeable when warm/hot , noise increases with speed, though goes slightly when off the throttle. Dip the clutch and all noise disappears completely. Sounds like a jet engine whoosh... So, pinion bearings? If so, who's had the work done and how much? Would rather rebuild than replace with a second hand unit as chances are it's only a question of time before thar goes bad too... Right?

Thanks guys.

 

[944 man]

You arent wrong in any of your assertions, but re-building the transaxle requires a special jig and there are very few people who can complete the job properly.

PHSportscars used to be one; but the Porsche fitter who did them at work in his own time, now works for Paul and runs the garage, so he doesnt have access to the kit any more. PH may be able to get the job done for you (he has someone from an OPC re-building 986 transaxles for him currently) and price-wise, hed probably be yourbest bet too.


Simon

 

[Jonny944CS]

I agree with Simon, a simple bearing change won't necessarily sort the problem.


Jonk if you can find someone willing to do a quality shimming job, using factory tooling, I'd be very interested to hear all about it.


I rebuilt my transaxle 2 years back, replacing all the roller bearings, seals and carefully making sure all the factory shim washers returned to their correct positions. The car was much quieter with the new bearings and the jet engine noise on the overrun has reduced significantly "" but, rather frustratingly, the noise is still there [].

If I understand correctly, the key to properly achieving quiet running comes down to accurate shimming of the ring and pinion gear positions to suit the tiny changes in position due to the new bearing tolerances (assuming your gear teeth are in good condition).

I tried to follow the workshop manual procedure, but my search fell at the specialist tooling hurdle. Most operations can be done with a standard dial indicator. However, determining the relationship between the diff axis and the pinion axial position is a little bit more tricky.

Factory tool used in the ring gear / pinion shimming process

 

[jonk]

Thanks guys, all a great help. Well these guys seemed to know their onions and are fairly close
http://www.sgmsportsltd.com/aboutus.html

Region of £1000 to do it and car off road for 5 days. Just weighing up whether to do it during summer or continue to put up with it. A chap I know with an 88 Turbo said his has been noisy for years and he's just done a fluid change and left it alone. It's only annoying on the motorway, round town etc it's fine. Hmmm.... Will have a think.

 

[pauljmcnulty]

Will have a think.

Have you been out in other S2s? Mine is outstandingly noisy compared with either my van or our Legacy, but for a 944 it's perfectly normal. Bear in mind how many different moving parts there are between the engine and the rear wheels on a transaxle car and you're in to the risk of spending money changing the wrong part anyway.

Get to any of the events where the 944 owners are attending and anyone would be happy to drive you around for a comparison. []

 

[jonk]

Cheers Paul, not yet been out in another S2 so, perhaps I need to sort that. I just can't believe it should be making that jet engine thrash noise when cruising and decelerating... Looking back at the service history it was first picked up about 6 yrs ago by Strasse of Leeds. The car has only done around 6000 miles in that time...
I'll get me to a summer event if I can and compare. Thanks.

 

[944 man]

I drove a Turbo Cabriolet that was nearly new (around 10,000 miles) and it screamed. It was louder than my old track car with its rear squab removed; and that had had a hard life before I got hold of it, let alone after.....

PCGB werent concerned - some really are noisy from new.

 

[pauljmcnulty]

Looking back at the service history it was first picked up about 6 yrs ago by Strasse of Leeds

Most will have this in the history somewhere, a customer complaining about the gearbox whine and a dealer covering there backside by stating that it's "all within acceptable limits".

They do make an unusual noise, so I'd ride in a few before commiting to a rebuild myself.

 

[TTM]

When I had the original rubber-centered clutch replaced on my S2 with the now usual spring-centered clutch, the transmission became noticeably louder. Replacing bearings in the transaxle tube afterwards did help a bit, but 40k miles later the noise is still there and hasn't got any worse.

 

[Jonny944CS]

ORIGINAL: TTM

When I had the original rubber-centered clutch replaced on my S2 with the now usual spring-centered clutch, the transmission became noticeably louder.

I have noticed this too. Maybe the rubber center has more capacity for damping/smoothing-out high frequency engine order pulses that tend to cause the gearbox to chatter when you back off the throttle.

 

[Mike_Pollock]

I have a decent looking rubber centred clutch if anybody wants to test the therory[8|][]

 

[tr7v8]

I'd always ask when the oil was last changed when people complain of noisy or baulky boxes. It may need several changes to get all the muck out. A good synthetic maked a huge difference to mine & quietened it considerably. A lot of the noise is that the torque tube acts to amplify & move the noise forwards. I suspect the torque tube is the case because the Alfa 75 I had was very quiet. That uses a rear mounted clutch & flywheel but a two piece prop of normal prop diameter instead of the 944s small shaft enclosed in a metal tube.
I've rebuilt transaxles in the past albeit not Porsche ones & generally careful building can get around the need for special tools, pinion height is normally the critical bit but can be sorted with patience. Once run in anyway a CWP set may never be quiet again as they may have taken a specific "set".

Oh & if anyone wants it I have an S2 box with LSD here for sale. []

 

[Jonny944CS]

Found a spec in the factory manual for ring-pinion backlash.

0.15mm (+/- 0.05) measured at 90mm from the diff output flange ctr. => 4 measurements at 90° intervals => Max permissible deviation 0.05mm.

I plan to check mine and report back. Pending the results, I may have another crack at the shimming.