NEW 915 parts out of spec or ??

[Trackrash]

I'm refreshing my '72 915 transmission.

I don't think this is the right bearing.
The new one has a 4 mm thick flange.
The old one has a 3 mm thick flange.
New...Part number 999-052-043-00-M100

Here is the old, original bearing



Then there is the new dog teeth and synchro ring.


It measures 3.381 and the speck is 3.393 - 3.407.

Any advice is appreciated.
Thanks,
Gordon

[James Brown]

Not sure but is that measured from the top of the dog teeth?

[Trackrash]

I'm measuring the OD of the synchro ring. The mic is just above the dog teeth.
The old synchro ring or the new synchro ring on the original first gear dog teeth measure in spec.
However the new synchro ring and new dog teeth together are out of spec.

[Jon B]

Gordon,

You have the correct bearing, the 3mm flange was '72 only and no longer available. Update your bearing clamp to match.

Synchro fit is a common problem with repro hubs. Your measurement of .012" under spec is really not acceptable. It will work, but won't last very long, as it's eliminating alot of effective synchro surface from use. Your choices are return it for exchange or refund, machine the dogs correctly or machine the synchro slightly to fit the hub within specs.

[Geary]

There is a small 9-degree angle that isn't cut onto replacement factory synchro teeth. This is usually cut after the new teeth have been pressed onto the idler gear.

Gerry Woods has a cutter which will pre-cut this small angle onto your uninstalled ring. Your synchro ring will then be compressed to the proper spec, rather than overly compressed.

[Trackrash]

Thanks for the update.

You have the correct bearing, the 3mm flange was '72 only and no longer available. Update your bearing clamp to match.

I can use a lathe to cut the recess in my bearing clamp to 4mm? Any problem with me doing this? I have a lathe, so I guess I need to fire it up.

.....machine the dogs correctly or machine the synchro slightly to fit the hub within specs.

Can anyone show how the dogs are machined? I have a lathe, can this be done on a lathe?


Thanks for all the help

[sjf911]

Originally Posted by Werkstatt

Gordon,

You have the correct bearing, the 3mm flange was '72 only and no longer available. Update your bearing clamp to match.

Won't this affect pinion depth and require remeasuring it and potentially reshimming the pinion?

[Jon B]

Steve,

The bearing flange has no effect on pinion depth, though worn clamps and worn shims do. I feel the depth should always be checked and adjusted regardless, as well as backlash and diff preloads.

[sjf911]

Originally Posted by Werkstatt

Steve,

The bearing flange has no effect on pinion depth, though worn clamps and worn shims do. I feel the depth should always be checked and adjusted regardless, as well as backlash and diff preloads.

So, in effect, as long as the final drive housing, pinion, and pinion shims are all the same and in tolerance, it shouldn't affect pinion depth to change the bearings and retainer?

[Jon B]

On a 915 it shouldn't affect the pinion depth, but it's always best to check regardless.

[Trackrash]

Has anyone machined the retainer? Would this weaken it?

[Jon B]

Gordon,

I spoke to Jacques at Scotts Porsche Parts in National City (just south of Sandy Eggo) , he has a new OE early pinion bearing with 3mm flange. Call him at (619)247-7495. Bring your bearings, clamp and problem synchro parts down to him, he has a full machine shop and can get your issues resolved.