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We have recently found that most or all clutch covers (diaphragm spring assembly) are supplied with clutch release bearing lands (the center bit held in place with a wire clip) that are not heat treated as they were originally. This leads to massive wear in as few as 1000 miles. The wear can be almost as much as the amount of clutch adjustment, so it is a serious problem. We have genuine AP and AP Racing ones that all have the same part fitted.

Of course, all modern release bearings are the type with the outer race only contacting the bearing land. In the old days, the flat-faced release bearings could not cause this kind of wear.

One can easily compare the new part to a heat treated one by using a file. It will easily remove material from the new ones, where as the old ones were hard and show no marks from the file.

Has anyone found a manufacturer who supplies covers with correctly hardened bearing lands?

I suggest anyone installing a new clutch assembly inspect and reuse their original part instead of the one fitted to the new cover.

Michael

its also good practice to inspect the 'wok' as well as earlier ones where not rebated as deep as the more modern ones.

using an early case with one of the modern deeper bearings, does, in some cases allow the bearing to run all the time on the landing plate - its impossible to adjust it to gain any slack.

the only way is to rebate the wok to give a bit more wriggle room

Thanks for the input Rich.

So you are saying it may be necessary with the modern release bearing in an old "wok" to machine some off the wok where the bearing withdraws to? Otherwise the bearing will be in continuous contact with the bearing land? Is that correct?

Michael7 wrote:Thanks for the input Rich.

So you are saying it may be necessary with the modern release bearing in an old "wok" to machine some off the wok where the bearing withdraws to? Otherwise the bearing will be in continuous contact with the bearing land? Is that correct?

yes, exactly that

We have never encountered what you are referring to. If the front of the release bearing had no clearance and was always against the bearing land of the clutch cover, it would be turning all the time and would "machine" its own clearance on the back side against the soft ally of the recess in the wok. We have not seen any with witness marks showing bearing contact in the pocket to which the bearing withdraws, but I do agree the early woks are about .100" shallower in this dimension compared to later ones.

The good news is that the current batch of GCK100 clutch kits that we have just received from MSC do in fact again have the hardened bearing land. So presumably the former batches with the unhardened ones is exhausted and AP Driveline have returned to the original spec.