Hilton

Yeah yeah, I know, "it can't be done"

I took this throwout bearing out of my '89 a few years ago when I replaced the entire clutch with the full GTS setup. I've been meaning to take it apart since then, and today decided in a few spare minutes to do so. Of course, I wasn't really planning ahead, so I didn't take any pictures in the 3 minutes it took to press apart .

First.. how to separate the rotating part of the release bearing from the spindle. There's no space there to get a puller in - tolerances are tight. Handily, there are three holes on the rear face, which I can only assume are there for taking it apart. The holes are just big enough for M8 bolts to fit into - so I grabbed three M8x40mm bolts, set them up in the holes, and then placed a flat piece of 5mm steel on top and pushed it with my shop press. I did also spray the top outer edge of the spindle (on the end on the bench in the pic below) with some penetrating oil, just to help lube it up.

Here's the bolts in-situ:



The interference fit is only about 3mm deep, so it doesn't take much pressing - next thing you know, the wheel part containing the bearing has dropped off (place something underneath the press to catch it.. I had a bucket as I wasn't sure whether I'd get a heap of ball bearings ). Once separated, what you'll have is the main spindle that moves with the release arm, and the rotating part which contains the bearing which fits in the pressure plate fingers. Here in this pic, I've already pressed the bearing out of the rotating casing, so its not sitting flush in there like yours will.



This casing is pressed onto the bearing itself. They're easily separated - I tightened up the casing in a pair of angle-irons that I keep on the press (very handy for supporting all sorts of stuff, including suspension bits). I pressed the bearing out of the casing with a 32mm impact socket, which easily passes through the hole in the casing. Again, the interference fit is only about 2mm deep, so the bearing will drop out on the first push pretty much - so have something underneath to catch it without nicking or scratching it!



And here's the casing still firmly in the holding irons - the lip is sitting on top of the irons in my shop press, so I wasn't relying on friction to support it, and it stays flat.





So finally, here's where I'm at - the bearing on its own, from top and bottom:





You can see its definitely not a standard bearing, so rebuilding with a new bearing would mean having some bits machined. In the last pic above, the lower ring inside the bearing is fixed to the outer race and doesn't rotate. The inner race including the part that protrudes from the middle do rotate.

More to come...

Hilton

I should probably add what my plan is here.. I haven't yet looked inside the bell housing of my '87 since I got it a couple of years ago, but its making a rattling noise with my foot off the clutch in neutral. Its either the release bearing, or the torque tube bearings, or both.

This bearing I'm dissecting came out of my '89 when I went to town on its clutch with a full new GTS setup, as the friction disk was worn. The bearing itself still feels good - no rough spots when turning under pressure, and still nicely greasy. So I'm taking it apart to repack with grease, and put it into my '87 when I go in there to replace the rear main seal and pilot bearing, and measure the clutch against the wear limit (from surface down to rivets per WSM).

If I'm lucky, the 87 doesn't need TT bearings yet (yeah right LOL), and I'll have a car which idles quietly at traffic lights.

Plan tomorrow is to:

1. Clean and measure the bearing and take more pics
2. Repack this bearing with high-temp extreme pressure moly grease
3. Put it back together over a few hours by heating/freezing various bits to reduce forces involved while pressing back together, and give myself every chance of having a bearing which feels perfect at the end of it.

I have no definite schedule for putting the repacked bearing into my '87, although I would like to get in there and do the pilot bearing sooner rather than later, as I'd rather not end up trying to dremel out friction-welded bearing race from the end of the crank.

Dave928S

So how are you going to repack Hilton? ... wash out and blow dry, then pressure pack from one side to the other???

69gaugeman

I haven't had one apart yet, but if you are repacking , just adding new grease in there should be fine. The amount of lubrication that it needs is amazingly small. That's why they last so long under the original pack. If you just add some more grease it will run for a very long time.

The problem with washing out the old and repacking, is that you can introduce contaminants into the bearing (bad) or not completely get out the solvent (whichever type you choose to do) and it will thin out the grease (also bad).

Jim Devine

A long time ago I watched an old mechanic re pack a T. O. bearing. What he did was to put it in a small can of grease, then put the can on a stove burner. The grease melts & flows into the bearing, then he took it off the stove until it cooled. The grease in the can became thick again, so his reasoning was that the grease that got into the bearing did also. Seemed to work.

WallyP

Hilton said, "I haven't yet looked inside the bell housing of my '87 since I got it a couple of years ago, but its making a rattling noise with my foot off the clutch in neutral. Its either the release bearing, or the torque tube bearings, or both."

Or possibly the plastic cup in the upper end of the release arm is faulty. That cup can be changed from the top - it's an interesting challenge, but it can be done.

Hilton

Yep, I'll clean it with brake cleaner while rotating, then lots of compressed air to get rid of all traces of solvent. I've got a conical bearing packer with a grease fitting - if I mount the bearing in it, there's a path through the bearing, so the grease gun will force grease through.

If its completely packed, there will be leakage - but looking at the rotating bearing case, there's a deliberate void in there which was filled with grease too when I disassembled, so I'll wipe off any excess, and expect expansion into that void as the grease heats up during operation.

Yes, given the state of the shifter cup when I got the car, I'm expecting the release arm cup to need replacing as well and have one to hand. I'll have a good close look at the ball too when I'm in the bell housing, as a rattling release arm beats them up a lot (I replaced the release arm ball in my '89).

More pics later today after I drop the kids off at school

I'm also pondering how these could be rebuilt with a standard bearing - depending on the state of the bearing out of my 87, I might have a go at that too, with the help of various local 928-owning engineers.

ROG100

Looks a lot easier than the earlier double clutch TO bearing which is NLA.
However pressing out the old bearing and sleeve and replacing with a new bearing and sleeve works pretty well.
It was also very easy to find a much better quality bearing than the original Porsche one - may be the same here if you need a new bearing on the later style - at least the TOB it is still available 8>).