BC

Where is it supposed to be. Some say that a TT vibration can start when the bearing carrier is pushed back too far from the front of the tube.

What would happen if it was RIGHT up by the tightened collar on the intermediate shaft? Would it be advisable to move it back?

It seems logical to me that it would be a good idea to reposition the carrier so as to have it in its rightfull position.

Leeroy has SEVERE TT vibration issues that I have isolated to the TT itself (clutch in, motor at constant revs, move shifter to lower gear, vibration ramps up as TT is brought up to rear end speed - correct me if I am wrong)

I was expecting to see the bearing all the way back. Its not. Its RIGHT up by the collar.

Benton

I'm a bit confused with your chronology of diagnosing the TT--maybe it's just how I'm reading it. If it vibrates with the clutch disengaged, it isn't the TT. Put the car in neutral with the clutch engaged. If it vibrates then (as RPM's rise), but not when the clutch is disengaged, it is very likely to be the TT. Something has to be wrong with the TT that can't be fixed with it in the car. Either the bearings are shot, or the center carrier has migrated north/south.

My TT vibrated at a resonant frequency around 5000 RPM, but not really any other time. The front carrier was about 12" back from the collar. When I rebuilt it, I drilled holes through the tube into the carriers and used self-tapping screws with blue loctite on them to locate the carriers. I haven't had any problems with this setup in about 8 track weekends of hard abuse.

BC

It can vibrate with the clutch disengaged if you are rolling at a certain speed to make the TT shaft spin at the speed it vibrates at - as it is in gear or getting synched to that gear.

Benton

Gotcha. Does it vibrate as well with the clutch engaged, at a stop, in neutral while revving? If so, the problem is 99.9% the TT. Unfortunately, as I'm sure you know, the only way to fix it is to get it out and figure out exactly what's wrong. At least it doesn't cost much to rebuild.

Do you know the location of the rearward bearing? It may have migrated forward.

BC

Yes, Mark - that is a very good point about the rearward bearing. I was laying under the car in my thoughtful position last night, and I decided that I would attack that investigation today. Because the car was up on stands for the clutch adjustment, and new transmission fluid. So I will be attempting some sort of measurement there as well, once I get to sears for that god damned 17mm hex bit that I swear I have bought twice already.

But yes, the vibration is present when you rev the car in neutral and then disappears when you put in the clutch to let the TT slow down.

SharkSkin

If the front bearing is right up against the forward clamp, then it isn't doing its job because it will be at the necked-down part of the shaft. I would expect it to vibrate like crazy with the bearing in that position. The front bearing really should be about a foot from the front flange; that's where mine started out before it migrated(original position just below the ball cup in this pic):



Rear bearing should be about a foot forward of the rear flange. You can check location with a piece of welding rod, coathanger, etc.:



These are the gauges I made up to monitor the position of my new "Constantine" bearing carriers:

BC

Thanks Dave. I didn't even think about the neck down thing.

Black Sea RD

Sorry to come late to this discussion but Dave A. nailed the diagnosis I would have given.

In automatic drivelines the rear part of the drive shaft also has a necked down area, although shorter in length, where this can also happen.

Cheers,

BC

The rear bearing carrier is confirmed to be about 14 inches or so forward.

I think that the front bearing is the main issue, and I have just some upstairs from getting it hammered back to about 8 inches back. Working for more soon. It moved back a few inches just by light pressure.

BC

How far back does the front bearing need to be? I see Dave's comment and picture. I may try to get a few more inches and then fix it with a small screw through the tube.

SharkSkin

If you are going to anchor the carrier in place, then I would say that as long as it's well past the neck-down you're good. With one in the center and the other two 12-14" in, you have no more than an 18" span of shaft running unsupported at any point. (rough numbers, I think the TT may be a bit less than 5') If the carrier were not anchored I would suggest at least a foot because... well, they move.

There is no clear spec, I'd say do what you think is right. Oh, might want to eyeball the center bushing that you are moving back -- it may have cracked if the shaft was slapping against it.

BC

So this is what it feels like to work on a car you can't take apart (Leeroy). I seem to have moved it to about 9 inches now. Maybe a bit less still. I used the clutch arm movement to push a socket extension back and move the carrier more.

I have to get a mirror. I need to see how the center bushing is doing - you are correct.

Got a good one - I didn't know the clutch covers changed the position of the slave cylinders in a twisting manner - so I hacked up a later cover - got under the car - and had to only use one bolt for the slave to get it to sit there so I could have my wife put the clutch in and I can adjust the T/H-things. Don't tell anyone.

Vilhuer

https://rennlist.com/forums/928-foru...and-tools.html

BC

Well, I put the bearing back to closer to where its supposed to be on Leeroy. I have not tested my fix yet, as I took the opportunity to adjust the clutch, replace the rack bushings, and replace the power steering pump. I pinned the bearing in its current location so it will not move forward... Hopefully.

Whomever worked on the car AFTER it was put together for the chick, but BEFORE it was brought back to 928intl, did some very interesting things with a brown snot-looking material. Including what may have been a 100 lb torque on the oil drain plug. Jesus.

There is also what I think is JB weld on the oil fittings by the pressure sensor. I'm relatively sure the JB weld would not have been on the engine Mark et all put in there.

Imo000

You really shoud have a good look at the TT bearing before pushing it back and pinning it. It moved forward for a reason, maybe the inner sleeve or the outter steel/rubber housing is or already felling apart.