johnb

I have just completed the rebuild on a '85 Auto torque tube, it only had 2 bearing carriers.

I have previously done:
'84 Auto TT it had 3 bearing carriers
'86 Auto TT it had 3 bearing carriers
'86 Manual TT it had 3 bearing carriers

Why would an '85 only have 2 carriers?

Mr porsche just make it up as they went along??

John

Vilhuer

AFAIK all automatic TT's had only two bearings when cars left from factory. All three bearing automatic shafts are done later, either by Porsche or aftermarket rebuild companies. Manual TT's have three except maybe very early '78 shafts.

Mark Anderson

We have rebuilt 646 torque tubes in the past 7 years and I do not remember seeing a stock 4sp AT with 3 bearings.

Mrmerlin

My 88 S4 auto has 3 bearings with the damper placed just ahead of the rear bearing, I rebuilt it myself at the shop, and i have rebuilt atleast 4 other TT`s and all of them have had 3 bearing supports

borland

I havn't rebuilt a TT, but I think the mounting locations should be equal distant to the flex plates so as to eliminate harmonics.

The damper size and location probably limits the ideal number to just two bearings for the 4-sp automatic.

chrly924s

Do bad TT bearings make a 'vibration' on deceleration? I have been sorting out different issues and this has become noticable lately.

Mrmerlin

on my 88 the front bearing was abour 10 inches in from the front edge, then the middle bearing was at just about the middle of the tube then the damper was placed into the rear about 20 inches(rear edge of damper) the the rear bearing was about 12 in. in from the rear, this is based on the wear/mating area inside the TT

Mrmerlin

not sure about your vibration problem but are the motor mounts and trans mounts good?
If they are worn then the motor will move forward upon braking,
Do you happen to hear a clunk or thud under hard braking ? If you do then its possible for the TT damper to be sliding back and forth in the tube this will eventually drive the bearing supports apart.
Also if you have replaced the motormounts with non factory parts then its possible that the lower mounting studs are hitting the top of the steering rack where it secures into the front crossmember, the stud s should be ground off a few threads above flush with the new securing nuts, you will need a good light and jack the car up to see if this is happening, remember that the rack can move on its mounts so if there is just a bit of clearance then this can be the vibe problem

chrly924s

The PO put MM's in back in the Spring. My wife says this vibe problem started after I had a new exhaust put on 3 weeks ago. I will look at the MM bolts like you suggest. It starts this when letting off the gas at about 50-60 mph.

Mrmerlin

Well i would also check the heat shields along the whole route of the exhaust , you could also have a broken exhaust hanger thats making noise or a broken heat shield attach point

chrly924s

it feels like small rumble strip in the rear.