C4S Torque tube/ central drive shafr R&R
10-01-2014, 12:23 PM
#1
Rennlist Member
Thread Starter
C4S Torque tube/ central drive shafr R&R
Having just replaced my C4S torque tube, I'll share some of the DIY highlights for those among you that choose to pick up tools ... and may ever be faced with such a job 
.
Prelude: I have no need to drive my car in inclement weather, and summers here are rarely hot ... so it's 98% driving with windows down: it was returning home recently one evening as fall approaches that had the windows up & heater on - heard a 'strange' noise from the front ---- bearing noise it was!!
Had I driven with windows up earlier, the failing bearing may have been detected sooner - no matter, as it was a long way from death but surely on a one way track to that end.
The bearing 'whine' was front & center: the front diff was the prime suspect - no joy in contemplating that $$$: I put the car in the air and scoped everything with engine running in gear & all wheels spinning - could not locate the noise: drained & refilled the diff (600 mls) and nothing came to a high power magnet when stirring the drains - OK so far ...
Sitting under the car with the stethoscope hanging loosely after a post fill scope check, I heard an occasional 'ticking' .... somewhat like when a kid sticks a card in the spokes of his bike - damn - it was coming from the torque tube.
It was the front bearing in the TT ( of 3 total) - no easy fix for that, but fortunately I had a spare TT in my extensive 993 parts collection.
Searching the archives for tips on the R&R, up comes MarkD's name as having faced this some time ago ... a quick ( and grateful) exchange of PM's with Mark gave me additional pre game warm up for the job - Thanks Mark!!
My friend Chris ( owner of a VW/Audi independent garage) was by to confirm the diagnosis, and to confer on a procedure for the job: it can be done by one, but would be a long and difficult PITA piece of work .... so we relocated to his hoist and did the job in 4 hours even.
Technique: Inside the car, remove shifter **** & boot and isolation rubbers on the shift lever. Then, remove most of the screws in the rear half of the center consul - just enough lift is needed to access the insulation cover over the rear top 2 bolts of the TT: 16mm heads, and two interlocked spanners are needed to crack these loose - no room for sockets .... they then spin out with two fingers, for that all the room there is.
Everything else is under the car - all bottom covers come off, front shifter rod, then the rear rod & shifter assembly can drop as a unit.
Three bolts hold the front diff mount - remove, lift the diff & the mount pulls out: remove the two lower TT bolts front & rear ... and the two pinch bolts from the rear drive shaft coupler ( to the front of the trans axle). The TT now comes off the rear dowel pin.
The TT & diff can now slide ahead ~ 2" - this greatly improves access to the top two TT bolts ( 15mm in front, 16mm heads in rear).
This is all the easy stuff - now, loosed the bolts holding the exhaust tips, ditto for the 6 bolts to chassis for the trans mount; this allows the nose of the transaxle to droop - but not enough.
We also loosened the front subframe; however, I'm not convinced that this was necessary - so if you're into this, hold off on this step.
At this point, ~ 1/4" of the trans splined shaft is holding up the TT .... this is where the 3 ft pry bar comes in ... The front diff is hard against the front bulkhead, and the trans drooped as far as possible: with the bar between the rear of the TT & trans, the entire engine & trans will move back the 6mm to clear the forward drive shaft splines ...
At this point, the TT drops at the rear - then, it is a wrestling match to pull it from the ~5" nose of the diff and out of the tunnel. Basically, job nearly done!
Note that the diff rear seals on the external surface of the female splined shaft of the TT - so do not let the diff tilt to the read, or it will begin to drain.
Major caution: there is a capped vent on top of the front diff - DO NOT allow this to get pressed against the bulkhead during any of these manipulations .... for if it is damaged/pressed inwards, venting ceases and seals will subsequently blow : they are not fun to replace ...
Reassembly is the reverse hahahaha
....... when the new TT is up in place, and some bolts loosely in the lower ears, first install the rear coupler pinch bolt to the prop shaft - not the trans shaft: there is slight longitudinal play in that shaft such that one of the pinch bolts may not clear the splines to find its home in the groove - with the front connected, a pinch bar can move the coupler ahead enough to get the second bolt in - you cannot do this in reverse order!!
That's it - car is perfect again: had I not had the TT, or had it been the front diff, Plan 'C' or 'D' centered on trying a 2WD conversion as an interim step - I have spare front axles, so simply acetylene cutting the outer CV joint bearing ring would free the outer cup/ABS ring & splined shaft - bolt in to replace the front half shafts, and remove the rear coupler on the TT; however, it is a better car for being a complete C4S.
.Prelude: I have no need to drive my car in inclement weather, and summers here are rarely hot ... so it's 98% driving with windows down: it was returning home recently one evening as fall approaches that had the windows up & heater on - heard a 'strange' noise from the front ---- bearing noise it was!!
Had I driven with windows up earlier, the failing bearing may have been detected sooner - no matter, as it was a long way from death but surely on a one way track to that end.
The bearing 'whine' was front & center: the front diff was the prime suspect - no joy in contemplating that $$$: I put the car in the air and scoped everything with engine running in gear & all wheels spinning - could not locate the noise: drained & refilled the diff (600 mls) and nothing came to a high power magnet when stirring the drains - OK so far ...
Sitting under the car with the stethoscope hanging loosely after a post fill scope check, I heard an occasional 'ticking' .... somewhat like when a kid sticks a card in the spokes of his bike - damn - it was coming from the torque tube.
It was the front bearing in the TT ( of 3 total) - no easy fix for that, but fortunately I had a spare TT in my extensive 993 parts collection.
Searching the archives for tips on the R&R, up comes MarkD's name as having faced this some time ago ... a quick ( and grateful) exchange of PM's with Mark gave me additional pre game warm up for the job - Thanks Mark!!
My friend Chris ( owner of a VW/Audi independent garage) was by to confirm the diagnosis, and to confer on a procedure for the job: it can be done by one, but would be a long and difficult PITA piece of work .... so we relocated to his hoist and did the job in 4 hours even.
Technique: Inside the car, remove shifter **** & boot and isolation rubbers on the shift lever. Then, remove most of the screws in the rear half of the center consul - just enough lift is needed to access the insulation cover over the rear top 2 bolts of the TT: 16mm heads, and two interlocked spanners are needed to crack these loose - no room for sockets .... they then spin out with two fingers, for that all the room there is.
Everything else is under the car - all bottom covers come off, front shifter rod, then the rear rod & shifter assembly can drop as a unit.
Three bolts hold the front diff mount - remove, lift the diff & the mount pulls out: remove the two lower TT bolts front & rear ... and the two pinch bolts from the rear drive shaft coupler ( to the front of the trans axle). The TT now comes off the rear dowel pin.
The TT & diff can now slide ahead ~ 2" - this greatly improves access to the top two TT bolts ( 15mm in front, 16mm heads in rear).
This is all the easy stuff - now, loosed the bolts holding the exhaust tips, ditto for the 6 bolts to chassis for the trans mount; this allows the nose of the transaxle to droop - but not enough.
We also loosened the front subframe; however, I'm not convinced that this was necessary - so if you're into this, hold off on this step.
At this point, ~ 1/4" of the trans splined shaft is holding up the TT .... this is where the 3 ft pry bar comes in ... The front diff is hard against the front bulkhead, and the trans drooped as far as possible: with the bar between the rear of the TT & trans, the entire engine & trans will move back the 6mm to clear the forward drive shaft splines ...
At this point, the TT drops at the rear - then, it is a wrestling match to pull it from the ~5" nose of the diff and out of the tunnel. Basically, job nearly done!
Note that the diff rear seals on the external surface of the female splined shaft of the TT - so do not let the diff tilt to the read, or it will begin to drain.
Major caution: there is a capped vent on top of the front diff - DO NOT allow this to get pressed against the bulkhead during any of these manipulations .... for if it is damaged/pressed inwards, venting ceases and seals will subsequently blow : they are not fun to replace ...
Reassembly is the reverse hahahaha
....... when the new TT is up in place, and some bolts loosely in the lower ears, first install the rear coupler pinch bolt to the prop shaft - not the trans shaft: there is slight longitudinal play in that shaft such that one of the pinch bolts may not clear the splines to find its home in the groove - with the front connected, a pinch bar can move the coupler ahead enough to get the second bolt in - you cannot do this in reverse order!!That's it - car is perfect again: had I not had the TT, or had it been the front diff, Plan 'C' or 'D' centered on trying a 2WD conversion as an interim step - I have spare front axles, so simply acetylene cutting the outer CV joint bearing ring would free the outer cup/ABS ring & splined shaft - bolt in to replace the front half shafts, and remove the rear coupler on the TT; however, it is a better car for being a complete C4S.
01-20-2020, 04:08 PM
#4
Bringing the thread back to life
The tranny on the 1984 died. The guy at Sterling Service on Broadway in Denver said it is the main band in the transmission. Quote is $4,500. I have a few questions.
1) How difficult is the removal job on a scale of 1-5? I am of modest talents but I have done lots of work with my buddy and he is excellent quality. I would fly him in from Ontario airport to Denver to do the removal.
2) How long does the removal take with one very skilled guy and one reasonably competent assistant?
3) How difficult is the replacement and how long does it take?
4) How much is a rebuilt 1984 automatic transmission?
5) Finally, I have seen some threads of replacing the automatic transmission with the manual transmission. I know it is a complicated process. As long as I am forced into this transmission job ANYWAY, should we do the conversion?
As always, thank you!
1) How difficult is the removal job on a scale of 1-5? I am of modest talents but I have done lots of work with my buddy and he is excellent quality. I would fly him in from Ontario airport to Denver to do the removal.
2) How long does the removal take with one very skilled guy and one reasonably competent assistant?
3) How difficult is the replacement and how long does it take?
4) How much is a rebuilt 1984 automatic transmission?
5) Finally, I have seen some threads of replacing the automatic transmission with the manual transmission. I know it is a complicated process. As long as I am forced into this transmission job ANYWAY, should we do the conversion?
As always, thank you!