worf928

Hopefully doc didn't scare you into your brown pants. Did you change the throw-out bearing? If you did, are you SURE that you did not get a GTS-spec t-o bearing (which has a larger inner diameter and if mis-matched with an old (smaller OD) guide sleeve will cause chatter.) I looked at PET after my first post and the t-o bearing for 79-86 is not superseded with the GTS t-o bearing like all the S4s/GTs. Thus, theoretically, you are not forced to use a new sleeve and release arm like the S4/GTs are when the t-o bearing is replaced. However, it is possible that you got a GTS-spec t-o bearing. The part number for the 79-86 bearing is 928 116 085 24 and the GTS bearing is 928 116 085 08.

Now, I don't know *IF* you could put a GTS bearing in an OB pressure plate. But, on the S4/GTs you certainly can put a GTS bearing in an S4/GT plate and woe to the clutch system if the guide sleeve and release arm are not replaced.

Sean79 5spd

Thanks for all the great comments. The spacer theory is interesting I will check. I will also try the Hupp method for centering the center plate.

The intermediate shaft is new ( $$$) and was greased so there should not be any dragging. As I did not resurface the flywheel the burnish patches could be an issue. Any suggestions for how to touch up the flywheel if I take out the clutch pack?

Thanks

gruffalo

my clutch was silky smooth, but dragging. I then adjusted the IP according to the equidistant method. It now releases better, but shudders somewhat.

I woud try playing around more with the IP. I know I will.

MM

docmirror

I discounted the burnished(burnt) flywheel because I thought it was surfaced, my bad. If the flywheel were removed and reinstalled, it should have been surfaced. I'm pretty sure the flywheel is keyed for installation in only one location on the crankshaft. As for the phugoid of the crank, that CAN cause this problem, I did not say it always is the cause. You crank is probably fine, but that is a possible cause.

The symptom remains, that the chatter is human induced. Once begun, it rapidly progresses to an out of control banging until the oscillation is removed (right Sean?). So, the TO bearing and arm seem to be related to this, but I also assumed that you used the correct parts when you did the job, and not just some stuff you had lying around the shop.

No chatter until the clutch job was done. What parts were replaced? What machining was done? I would investigate the parts replaced first, with the PP and clutch plates suspect(see below).

Here's more bore-you-to-death facts about the coupling of an internal combustion engine to a running drive system; Ya know those little springs that are mounted sideways in most clutche plates? They are there to reduce the torque coupling force of the engine and take up the impluse produced by the engine as each piston pushes the crank 4 times per revolution. Many, but not all clutche rebuilders just reuse the old springs, assuming they are within spec. If the springs have been overheated, they may be compressing to the limit(spring bind) on each engagement, thus defeating their intended purpose of impulse decoupling. Hmmmmmmm?

Doc 90GT in resto.

Garth S

As Doc said, machine surfacing in the norm; however, when I did the clutch thing on my '80, the flywheel stayed in* and was treated to a cross hatching with 80 - 100 grit emery cloth wrapped on a small wood block - ditto for the intermediate plate.
That was ~10 years ago - and the clutch is still as smooth as buttaaa ....

* the RMS was dry and the flywheel passed the flatness test with a machined straight edge

hupp

Sean,

The flywheel may be your smoking gun - depending on its condition. I would inspect and have it resurfaced if you observe some hot spots. Typically, one would grind the flywheel to resurface; however, the '79 flywheel has a lip around the outer diameter (used to center the clutch pack) so grinding is not an option.

My flywheel was resurfaced by chocking in a lathe and cutting, similar to brake rotor refinishing. This has to be carefully watched and the cutting tool must be backed off before reaching the outer lip. Also, very small amounts should be removed with each pass. The flywheel surface finish and minimum thickness is spelled out in the WSM.

Sean79 5spd

Garth & Scott, your were on to the solution. I used 200 grit sandpaper on the flywheel and intermediate plate. Probelm solved. Moral of the story, never replace clutch without resurfacing old surfaces.

Thanks guys

hupp

Sweet!

Sean79 5spd

OK, one problem solved, that was the shudder in reverse. Now it slips in 3rd & 4rth under hard acceleration.

Any thoughts? This is beginning to really **** me off.

Sean

gruffalo

are you sure the rod from the slave to the arm is properly seated in its correct position?

mm

hupp

Sean,

Check the pre-load on the clutch pedal rod. Set the pre-load by:

- Loosen the lock nut.
- Loosen the rod until it can easily be slipped on and off the clutch pedal boss.
- Pre load rod by approx. 1/4 turn
-Tighten lock nut.

Its possible that too much pre-load on the master is preventing your clutch from totally engaging.