[LivingDust]

I was reading some of the reviews of the 968 from magazines articles online. I thought I read something about the rev limit set to 6700 to protect the Transaxle (not the engine.) But now I can't find that article to prove it that I read it.



In any case, I installed the Promax 7700rpm chip, and I like it. I took it a couple of times just over 7000 as test. What surprises me is how in second gear the transaxle seems to feel wrong at that RPM. In fact I can rev it up that high in second and than press the cluch and let the engine idle. With my hand on the shift knob it feels like there is something off balance and it makes me nervous.



Even with the clutch in, the tube from the engine to the transaxle is spinning at 7000+ rpm. Can it be re-balanced?



I have already blown one tyranny (maybe a freak flaw in my original `92 transaxle) Now I have a used `94.



So my question is whether anyone else knows of any RPM issue with the transaxle? And since I senses something like a wobble, should I be concerned about my car in particular?



Scott

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[flash]

with the clutch in, the shaft inside the tube is not spinning - you can verify this by pulling the inspection cap in the tube and peeking in there - it spins when out of gear, but stops wheen you step on the clutch



if you have a vibration at 7k with the clutch pedal in, i would be looking at other areas - does it do it in all gears, or just second? does it do it in nuetral? does it do it when sitting still?



yes, i would be "concerned" - something sounds out of whack

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[BruceWard]

What surprises me is how in second gear the transaxle seems to feel wrong at that RPM. In fact I can rev it up that high in second and than press the cluch and let the engine idle. With my hand on the shift knob it feels like there is something off balance and it makes me nervous.

with the clutch in, the shaft inside the tube is not spinning - you can verify this by pulling the inspection cap in the tube and peeking in there - it spins when out of gear, but stops wheen you step on the clutch

Are you suggesting that the shaft inside the torque tube is not spinning when rolling down the road while the clutch is depressed?



If so please explain further.



As far as I am aware the shaft inside the torque tube is directly connected to the transaxle and if those wheels are spinning the shaft is spinning.



When the clutch is depressed the torque tube shaft is disconnected from the flywheel and engine but remains connected to the transaxle and wheels.

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[rustech]

The clutch disengages the flywheel from the drive shaft in the torque tube...neutral disengages the drive shaft from the wheels via the tranny.

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[BruceWard]

As far as I am aware the shaft inside the torque tube is directly connected to the transaxle and if those wheels are spinning the shaft is spinning.

Oops I should have added "unless you are in neutral and the clutch is in".

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[flash]

i wasn't talking about rolling down the road - i was indicating how to see that the shaft is released from the engine when the clutch is depressed



i presumed nobody would have it in gear while they were under the car and the engine was running, so of course it would be disconnected from the transaxle

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[LivingDust]

So to clarify: What I meant was I was rolling at aprox. 60mph in second gear with the clutch to the floor (is that in or out?) The engine reving ar 7k+ was not making any kind of dangerous sounding noise, but the vibrations or winding noise from the tranasaxle concerned me.



I can not say whether the off-putting sound is from the driveshaft or maybe the synchros? But something seems to be straining to keep up that kind of RPM. I can also cause the worrisome vibrations If I try to downshift to 2nd from 3rd and that speed. I can sense the synchromesh system trying to spin up the shaft or something else to a very high RPM.



Can things get off-balance, and if so is there a way to rebalance anything without a tranny rebuild?



Scott

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[flash]

lots of things can be doing this



a bad bearing or synchro in the transaxle can cause this



while less likely, an out of balance DMF with bad rubber can do it too, but it would be in all gears - high rpms is a typical point where this kind of thing shows up - it would be out of the spec area of where the DMF could do its job



a bad torque tube bearing can do it too, but again should be in all gears



if it is only in second, i suspect you may have a bearing going away on that gear, or a synchro going away - second, and that syncro get the most abuse



drain your transaxle and look at the fluid - look for any metal filings or flecks - when you bounce light on it you should have no "pretty" metallic looking oil



you may actually be ok though - these are very sloppy boxes - a bit of buzz is not uncommon - check the oil to be safe though

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[Greimann]

[quote name='flash' date='Aug 29 2005, 03:03 AM']l...you may actually be ok though - these are very sloppy boxes - a bit of buzz is not uncommon - check the oil to be safe though

[right][post="9317"]<{POST_SNAPBACK}>[/post][/right][/quote]

Yea this isn't a Honda box. Maybe find another 968 to drive for comparison before tearing into major mechanical work.

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[LivingDust]

Thanks for the advice. I tested 1rst today, and it seemed the same. If I try to shift down into it while rolling at a speed near or at the top of the max shift-point it fights me a bit, and I seem to feel/hear lots of things trying to speed up in order to mesh. It just feels, well maybe sloppy is the right word. But mostly like it just wasn't designed to spin that fast.



So what about the article reference. I swear I read something about the rev limit protecting the transaxle in on article, but I can't find it now. So am I crazy? Or does can someone confirm they read that too?



Of all the things on my car, the tranny makes me most worried, because this is a used '94 that is replacing my blown `92 transaxle.



Again, thanks for your advise and help!



Scott

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[flash]

lol - i don't thnk you're crazy, but i've never heard of there being a problem with rev limits and the transaxle - that doesn't mean that it doesn't exist



if you have a problem in every gear though, you may just have an input shaft bearing issue, or something along those lines



are you sure it's in the transaxle? does it do anything odd while sitting still? in gear with clutch in? out of gear with clutch in and out?

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[LivingDust]

No the only time I feel the symptom is when the rolling speed of the car combined with the gear I am in or am shifting to spins the drive-shaft near the rev-limit of the engine, whether the engine is engaged with the clutch or not. I can reproduce it in first & second, but I have not tried going fast enough to reproduce it in third or higher.

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[flash]

ok - well, that's probably not a good idea anyway, since you'd be doing 100 or so



since i'm barely brighter than the furniture, let me verify the following:



rolling at speed, out of gear, clutch in, engine at 7k - problem?

rolling at speed, in gear, clutch in, engine at 7k - problem?

rolling at speed, out of gear, clutch out, engine at 7k - problem?

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[LivingDust]

Assuming that "clutch in" means my foot is pushing the clutch pedal to the floor and the engine is disengaged...



[quote name='flash' date='Aug 29 2005, 03:54 PM']rolling at speed, out of gear, clutch in, engine at 7k - problem?

[right][post="9351"]<{POST_SNAPBACK}>[/post][/right][/quote]

No, not a problem.



[quote name='flash' date='Aug 29 2005, 03:54 PM']rolling at speed, in gear, clutch in, engine at 7k - problem?

[right][post="9351"]<{POST_SNAPBACK}>[/post][/right][/quote]

Yes, around 37-40mph in first, and 57-61 mph in second



[quote name='flash' date='Aug 29 2005, 03:54 PM']rolling at speed, out of gear, clutch out, engine at 7k - problem?

[right][post="9351"]<{POST_SNAPBACK}>[/post][/right][/quote]

Yes, same as with the clutch in.



So the engine engaged or not engaged seems to be a non-factor. This would seem to eliminate the clutch as well.

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[flash]

ok - so the only time it goes away is when you isolate the driveshaft



the only thing left to determine is whether or not it remains unchanged when you pop it out of gear, but leave the clutch released, and then coast down 15mph or so from the speed at which 7k correlates



if it remains unchanged, then i think it is torque tube bearings



if it changes, then i think it is in the transaxle, and likely something like input shaft bearings



this all presupposes that this is a new condition, and not something that has been there all along



i would drive some other 968s and see if they are the same before yanking anything out



also, you could try putting straight 140 gear oil in the transaxle to see if it changes - don't leave it in there though - it really won't hurt anything, but it will be very tough to shift by comparison



again though, these are not quiet boxes, so it may just be something normal - you should hear what the transaxle sounds like when you install a single mass flywheel

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[LivingDust]

It's the torque-tube! Read $$$$



Wednesday morning I was puzzled by bird-chirping coming from underneath my car. It really sounded like bird chirping!



My mechanic says it is the bearings in the torque-tube. Unfortunately Porsche does not sell these bearings nor a kit for repairing the torque tube and a replacement torque-tube is something like $3400.



We are exploring all options at this point including having some bearings custom made and getting a torque-tube from a salvage yard.



Any advice or ideas?

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[flash]

928 International - $495 to rebuild yours plus 2 way shipping and your R&R - great job on mine

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[Brian]

living dust-

my torque tube chirped like a bird this spring when the weather was still chilly here in mich. also, the car had sat in a garage all winter.

i took it to two mechanics who wanted $5k to replace it. the part new is around $1k, but the labor is extensive.



while i pondered changing the tube, i continued driving it. both mechanics said it was a concern, but not a major problem until i felt vibration, etc.



so as i drove it, the sound went away. i haven't heard it all summer.



i figure my scenario was just a little rust in the bearings from sitting all winter.



not saying you don't have a problem, just sharing my experience.

if you haven't driven it much lately, it may work itself out.

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[flash]

the labor is about 9 hours - you have to R&R the transaxle - that's good for up to a grand, depending on your shop



the rebuild is $495



the shipping is going to be as much as $200 round trip (less if you use greyhound, but it means as much as 2 weeks total waiting)



worst case though, this should not cost more than $1700 if you have someone else do everything

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[Brian]

good point -

i should have said that the detailed estimate i had was from a guy who thought ours was the same as a 944. our car, you don't have to replace the clutch. from what i hear, on a 944, you do. so his bid was way overinflated.

the bid from the dealership wasn't detailed. i don't know what their price was all about.

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