Spun Pinion Bearing Race Removal

[KFJ_SC]

In the midst of my 915/63 (Al case) rebuild and sure enough the pinion bearing race is spun. I've read the many threads on the variety of fixes and have decided to give the loctite 660 a try. The race does not (to the naked eye/finger) move side to side, in fact, it is tight enough that I can't get the race out. I've tried spinning the race and pulling and no joy. Anyone have an idea on how to get the race out? Perhaps heating the case? Anything else?

-Kirk

[HawgRyder]

Old trick is to fill the cavity in the flywheel with grease,, then hammer in a rod that fits the hole as tight as possible.
The hydraulic effect will push out the bearing, or ring, or whatever.
Bob

[Grady Clay]

Kirk,

Is it that both bearings won’t come out or just the roller bearing outer race?

There exist blind bearing pullers that work best. I’ll discourage you from attempting to tap it out. Given the marginal interference fit, you don’t want to “cock” it in the bore.


Just to repeat it here, Porsche made the input shaft roller bearing smaller in order to leave more alu between the two roller bearings. This change happened mid-year with 915/67/68/69 and 70. All 915/72/73 has this change. The earlier 62 mm bearing is 930.302.391.00 and the later, smaller 55 mm bearing is 999.110.032.00.

Best,
Grady

[ChrisBennet]

You are definately going to need to use heat to expand the aluminum case. I'm heading to bed else I'd look up the tempurature in my manuals.
-Chris

[KFJ_SC]

It is just the outer race (not the bearings) that won't come out. Shop manual says heat case to 250 and use a Porsche tool to punch it out from the diff side - which would be fine if the diff wasn't in there still . I'll try heating the case with a torch and see where I get with it.

Grady - mine's a 915/63 and the input shaft bearing is smaller.

[KFJ_SC]

Putting some flame to the case did the trick - she's out!

[Grady Clay]

Kirk,

The problem is that it is difficult to drive out from the differential side even when the differential is removed and using the P-tool. There isn’t a “straight shot” on axis with the pinion bearing bore. The input shaft is a different deal.

Pretty much the only way to remove it is with an appropriate “blind” puller from the forward end and use (judicious) heat. I would get everything equally very hot (220F) and then put dry ice on the bearing race. You can do this with the P-tool in dry ice or liquid nitrogen. It should fall out if facing down (bell housing up).

BTW, how is it you have your 915 apart and not have the differential assembly out? At LEAST you should replace the two axle flange seals and the differential side-cover O-ring.

Be careful when handling the differential assembly, the lower taper roller bearing can fall off - along with the adjusting shims. I always put my fingers around to the far (starter) side to retain the bearing. Do this both removing and installing.


Please measure the OD (outer race in the case) of the input shaft roller bearing next to the 4-point ball bearing. It should be 62 mm or 55 mm, which one?

I ask because posts and even Porsche official documents can have errors. It is up to us to correct them as we go. This is one of the finest features of Pelican; it is self correcting. Of course I’m picky and trying to get every silly little detail correct in Pelican archives.

Best,
Grady

[KFJ_SC]

Grady,

Sure enough, my input shaft bearing race is 62mm - I misread your first post as saying the input shaft race is smaller THAN the pinion shaft race (which it is). I now understand you were simply saying that they decreased the size from 62 to 55. My apologies.

thanks for the tip on axle flange seals and o-ring - these are now on order.

[gtihop]

I had the spun bearing race in mine last fall, used loctite to retain it. The problem is making sure that the pinion bearing is in exactly the same place as it was before or you run into differential set up problems.