SLFM

[Cater_Racer]

Yesterday at Silverstone we suffered Sudden Loss of Forward Momentum Tom was driving, after casually dismissing a tail-ender into the grasslands (using my lovely new GRP front wing) half a lap later upon exiting the chicane in 3rd he changed up but found he had box full of neutrals. He ground to halt shortly after crossing the start line and was towed back to paddock post race.

The problem seems to be torque tube??? the gear selection seems fine, the clutch feels normal, engine fine. However with engine running and clutch suppressed you can select any gear, but upon releasing clutch Nothing. Nix, SLFM.

No nasty grinding noises or any external evidence of failure. Is this the torque tube splines? Does anyone have similar experience?

Tom will probably take this on as self repair job, using Clarks Garage for reference, or is this stupidly optimistic?

Whether or not I let him repair the front wing and badge panel will require me to be convinced it won't look like a dogs dinner when he's finished.

 

[zcacogp]

Gerry,

'Tis a rum one, to be sure. Having thought about it I think your two observations as follows are most relevant;

- The clutch and gearbox both felt entirely normal to use; the clutch had the usual springiness in the pedal and the gearlever responded as you'd expect - there was resistance and a tactile gate. It appeared that everything was happening as it should apart from the drive.

- If there had been a break of some driveshaft or spline somewhere then there would be the broken ends of metal rubbing against each other somewhere, which you'd hear or feel. Tom didn't experience any odd noises and neither was there anything amiss when trying to move the car afterwards; you put it in gear and released the clutch and everything was normal other than a notable lack of forward progress.

I find myself wondering whether there has been some kind of failure to mesh in the gearbox. Is it possible that a final drive gear has slid along a shaft somehow and is failed to connect with the next gear in the chain? This sounds daft even as I type it but may illustrate the line of my thoughts.

A self-repair is not stupidly optimistic. There has been a failure of some sort between the flywheel and the output drive cups from the gearbox. If Tom tackles it as a clutch change (which requires the removal of everything up to the flywheel) and checks every drive component that comes off to make sure it works as it should then he will come to the problem at some point. And it'll be a single point of failure so probably only one thing to replace (but doing the clutch at the same time is sensible). A clutch change on a 944 is not a difficult job, it's just a long one.

I also reckon that the wing is repairable although whether acceptably so depends upon how messy a bowl of pedigree chum looks when served.

If Tom wants a hand (pre- or postnuptuals) then I'm quite happy to trundle up to P'Bro and wield a spanner with him.

Oli.

P.S. To add to the misery of the day, my S2 also broke on the way home! The gear linkage snapped, although I limped home (3rd and 4th gear only) and thankfully had the spare parts to replace it in my workshop. Between your race car, Tony's pretty yellow one going 'bang' and mine it wasn't a great day out!

 

[Monkeythree]

Sounds like clutch or diff. Just wondering if the diff was on it's limit during the tail ender and if it was suddenly snapped out of it then perhaps something went pop in there?

 

[Cater_Racer]

Sounds like clutch or diff. Just wondering if the diff was on it's limit during the tail ender and if it was suddenly snapped out of it then perhaps something went pop in there?

That's a valid thought Tnx.

 

[Cater_Racer]

Thnx Oli I don't think it's gearbox, as you say it feels right, the clutch feels right to.

It could be the diff as M3 says, I think that's a definite maybe.

Either way it will be post nuptials as Tom's moving house in August (if they've finished building his new one) so he won't want a disassembled 944s2 as well as his other 944s2 to move. So the plan is for me to deliver the car down to P'bro early September. I'll hold fire from ordering a refurb torque tube until he's done the investigatory work.

 

[zcacogp]

Gerry,

Diff is a good suggestion from Tom (Monkey3). I don't know what fails in them but a failure after the gearbox and before the drive to the driveshafts would indeed explain it. Would one fail as silently as you experienced (i.e. no noises or rumblings)? The fact that the slight bump beforehand may have contributed in some way is a very good point.


Oli.

 

[robwright]

Surely if you can engage all gears with engine running then it has to be something diff or final drive related?

 

[924Srr27l]

Yesterday at Silverstone we suffered Sudden Loss of Forward Momentum Tom was driving, after casually dismissing a tail-ender into the grasslands (using my lovely new GRP front wing) half a lap later upon exiting the chicane in 3rd he changed up but found he had box full of neutrals. He ground to halt shortly after crossing the start line and was towed back to paddock post race.
The problem seems to be torque tube??? the gear selection seems fine, the clutch feels normal, engine fine. However with engine running and clutch suppressed you can select any gear, but upon releasing clutch Nothing. Nix, SLFM.
No nasty grinding noises or any external evidence of failure. Is this the torque tube splines? Does anyone have similar experience?
Tom will probably take this on as self repair job, using Clarks Garage for reference, or is this stupidly optimistic?
Whether or not I let him repair the front wing and badge panel will require me to be convinced it won't look like a dogs dinner when he's finished.

Could it be the connecting Sleeve (No.14) that joins the torque tube to the gearbox input shaft which has failed ?

Bob Lewis would be able to stick it on his ramp and check this... ?

Who's / where P'bro ?

R

 

[Cater_Racer]

Surely if you can engage all gears with engine running then it has to be something diff or final drive related?

Not sure Rob, that might be a good call, but you can select gears with engine off, so it might be TT or clutch. When we get the car down to P'bro you can come round and we'll have a investigation.

Gerry

 

[924Srr27l]

Surely if you can engage all gears with engine running then it has to be something diff or final drive related?

The Motor can be running and the 1" Shaft in the TT spinning / turning but if this is not connected to the gearbox
input shaft? you could sit there all day and operate the gear linkage with no effect.

It's either a connection in the TT shaft or something inside the gearbox that has broken, but normally there would of been some noise!

R

 

[924Srr27l]

Bargain !
http://www.ebay.co.uk/itm/Porsche-944-turbo-951-transaxle-gearbox-UY-code-87-88-/122478944277?hash=item1c84506015:g:f1UAAOSwNnRYlLsK


R

 

[marojojoem]

Not sure if its helpful but I had exactly the same symptoms on my 1985 Lux.

I had it trailered away to my local indy fearing the worst, turns out the bolts holding the splined collar onto the clutch assy had unwound and fallen out, new bolts and I was sorted, couldn't believe my luck

Mark

 

[Cater_Racer]

There's an inspection hole / access cover in the area where the Torque Tube mates with the transaxle - on the Right hand side IIRC. If you pull out the rubber bung you can see where the TT shaft connects to the gearbox input shaft via a splined sleeve - this could give you more information on where to look next.
HTH

 

[Cater_Racer]

That is interesting Mark, I'll get under it tomorrow and check that one!!!!

 

[Cater_Racer]

Thanks Steve, I'll look out for it 2morro.

 

[robwright]

This is true there is an inspection cover to disconnect the torque tube from transaxle. Thinking about a TT failure of some sorts would also produce the same result engine running or not as the transaxle just simply wouldn't be driven at all. Maybe it is just a splined connector failure? Fingers crossed. Strange how no nosie though? When my clutch failed I had partial drive and it sounds like a bag of spanners, which got transmitted to the back end by the TT. Just the centre of the clutch that had failed that's all. Is it time for a sweep stake?

 

[Cater_Racer]

Update. Got the car up in the air, found the inspection holes. The clutch bell housing is solidly bolted to the TT (so not Mark's issue) and thru the inspection hole I can see the flywheel and clutch rotating smoothly with the engine ticking over in Neutral. So seemingly nothing wrong there. However at the gearbox end I popped the inspection bung off, and the the TT is not rotating! (so not gearbox failure or diff). so switched engine off and put hand in thru said hole, and the TT rotates freely by hand, it feels smooth and very correct, only with the clutch out in neutral you'd expect it be connected directly to the crankshaft. It certainly is not! So it all points to a clutch spline failure.

So it looks like over to you Tom, new clutch.

Gerry

 

[Cater_Racer]

Thanks Roger, I found the same diagram.

P'bro is Peterborough where Tom lives. Not far from Rob Wright's abode.

 

[924Srr27l]

Thanks Roger, I found the same diagram.
P'bro is Peterborough where Tom lives. Not far from Rob Wright's abode.

Ok so hopefully it's the clutch plate splines that have broken and not the Torque tube shaft like this one...

Pbro, Where i was born and lived near the Lincs/ Cambs border for 18 years...


R

 

[Tommys86]

ok great so sounds like it's engine end rather than rear.. a new clutch... anyone recommend any other jobs to do 'whilst your there'? Thinking maybe flywheel replacement? Rear end oil seal? TT bearings?

Performance improvements - the clutch itself? For example is the turbo clutch compatible and perceived to add performance?

Long shot.... any weight reduction opportunities?

Tom