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Discussion Starter #1
I have frequently observed the "creeping" input pinion needle bearing race when inspecting final drives.

This problem, in its end stages, is known to destroy a FD by wearing through the housing and interferring with the speedometer sending ring in pre-2002 final drives, or the tapered roller bearing in post-2002 final drives.

I have speculated that the creeping of the bearing race might be due to lack of a proper interference fit between the race and its seat on the pinion shaft.

This is the first time I have seen a complete lack of interference fit allowing removal of the race from the pinion shaft with finger pressure.

This suggests to me lack of an interference fit is the cause of this problem.

Anytime a FD is rebuilt, this problem should be looked for. The creeping input pinion needle bearing race can be identified without disassembly of the input pinion assembly, however, to correct the problem requires that the pinion shaft be removed from the housing.

This is from a pre-2002 final drive. I'll clean the surfaces and seat the race with Loctite 660.
BTW this was an incidental finding during rebuild following a classic crownwheel bearing failure due to over-shimming by approximately 0.15mm





 

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Thanx for a great update Curtis........and timely too.........High temp today expected to reach 30 F........with just the slightest hint of the appearance of snow fairies.........just about time for ol' Dollar to head to the barn for some maint.......... :D
 

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Just trying to make certain that I'm clear on the creep. Is photo #3 showing the gear creeping toward the left, pushing the bushing/race away from the shaft? If so, is the overhang of the race the distance that the gear creeped?
Thanks Curtis, for all your work.
 

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Discussion Starter #4 (Edited)
fpmlt said:
Just trying to make certain that I'm clear on the creep. Is photo #3 showing the gear creeping toward the left, pushing the bushing/race away from the shaft? If so, is the overhang of the race the distance that the gear creeped?
Thanks Curtis, for all your work.
Sorry for the confusion. Lacking a video of showing the race sliding on and off the shaft with finger pressure, I chose to post three pics showing the race on the shaft, half way off the shaft, and completely off.

When I opened the drive I could see that the race was about 2mm from being fully seated. So I knew it was "creeping". I didn't know how loose on the shaft it was until I disassembled the pinion shaft.

I have previously posted pics of what a displaced race looks like from inside the the FD with the pinion shaft still assembled. I have also posted pics of what happens when the creeping race destroys the tapered roller bearing. I'll have to dig around for those old pics.

Addendum: Okay, here's a pic of what happens when the creeping race eventually wears through the aluminum housing:
http://www.bmwlt.com/forums/showpost.php?p=488737&postcount=9

Here's a post about another FD with a creeping input pinion needle bearing race. In the past I have found that the races were pretty tight on the pinion shaft, just displaced. The interesting thing about the FD that caused me to start this thread is that the race was finger loose.
http://www.bmwlt.com/forums/showthread.php?t=61159&highlight=input+pinion
 

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Wrencher Extraordinaire
2005 K1200LT
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My 05 also had the creeping race but I had to remove it with a puller so I could clean it up and I used Loctite Sleeve Retainer as I did not have a gap to fill and this requires about 400 degrees to release. I think it is on there. By the way thanks for the 2.7mm shim, it put the backlash right at 0.006.
 

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No and it would be difficult to preload a taper bearing here as the position of the pinion is established by a shim and the ball/roller bearing combination on the other side of the gear. That shim sets the contact pattern on the pinion/ring gear. This roller bearing just takes up the load from the ring gear on the pinion.
 

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Thanks John, I was just thinking in terms of preventing the creeping. I can certainly see where it would be a pain to get it set right if it were built that way.
 

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I still don't think we fully understand why the creep occurs. Finger tight I can see it but I needed a puller to get mine off.
 

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Charlie, maybe I've missed an earlier conversation but I've been thinking (I know, that's a dangerous proposition). Is it possible that over shimming the crown wheel could put undue pressure on the pinion nose bearing and thereby cause a slight forging effect that would loosen the fit of the bearing in the case or on the inner race shown in the pictures? Or am I missing the mark here?

Robert
 

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Discussion Starter #11
jzeiler said:
I still don't think we fully understand why the creep occurs. Finger tight I can see it but I needed a puller to get mine off.
Agreed. This is the first I've seen that was finger loose; that's why I decided to post about it. Wanted your input and thoughts from other professionals as to causes.

All of the other cases of the creeping pinion bearing race that I have seen also required a press to remove/replace.

I just speculate that if one is really loose, others might be lacking proper interference fit even though not finger loose. Additional reasoning in support of this theory is the lack of proper interference fit in other areas of some final drives. i.e. the spinning tapered roller bearing and the more rare spinning aluminum component in the crowngear assembly. Dare I suggest that bMw had lathes that had trouble staying in calibration, labor problems, industrial sabotage? ;)

Further investigation might involve measuring the ID of the race and OD of the shaft and calculating the interference. Mechanical engineers should be able to tell us what the minimum interference should be.

I think your procedure of completely removing the race and reseating with Loctite sleeve retainer is the right way to go.

Thanks.
 

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Discussion Starter #12 (Edited)
Scouter-50 said:
.... Is it possible that over shimming the crown wheel could put undue pressure on the pinion nose bearing and thereby cause a slight forging effect that would loosen the fit of the bearing in the case or on the inner race shown in the pictures? ....
I don't think over-shimming is directly related to the creeping pinion needle bearing race.
The crown gear is separated from the pinion gear by the backlash setting.
The back lash setting is determined by a shim under the tapered roller bearing.
I doubt that even a seriously over-shimmed crown gear assembly would eliminate the backlash.

The dynamics between the pinion gear and crown gear are complex under acceleration/deceleration. Acceleration and deceleration causes forces on the pinion shaft in both axial and radial directions. The pinion shaft resists radial movement by virtue of the the bearings around the shaft, and resists axial movement by the presence of the "locking ring" which secures the large pinion bearing in the housing. However, there will be micro-movement of the pinion shaft due to bearing tolerances and flexure of components. You can think of these micro movements of the pinion shaft as "wobbling around" in its housing. My theory is that this micro "wobbling" of the pinion shaft, coupled with a bearing race that lacks proper interference fit, causes the creeping race.
 

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From my feeble memory Paul Glaves wrote about this problem last year in the BMWON magazine. I believe he also mentioned there was a possibility that the shaft was under or oversize on the large ball bearing also. Seems like these are rare but still another thing to check.
 

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Discussion Starter #14
bigbear said:
From my feeble memory Paul Glaves wrote about this problem last year in the BMWON magazine. I believe he also mentioned there was a possibility that the shaft was under or oversize on the large ball bearing also. Seems like these are rare but still another thing to check.
I recall Paul's article about the spinning aluminum component in the crowngear assembly. I don't recall him writing about the input pinion needle bearing race.

Does anyone recall what issue Paul's article about the crowngear assembly was in?

Thanks.
 

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CharlieVT said:
I recall Paul's article about the spinning aluminum component in the crowngear assembly. I don't recall him writing about the input pinion needle bearing race.

Does anyone recall what issue Paul's article about the crowngear assembly was in?

Thanks.
Charlie, I will PM Paul's e-mail address to you. He will answer with no problem.
Robert
 

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Just finished replacing the crown ball bearing in my '05 FD and noted during final inspection before reassembly that my pinion shaft needle inner race has crep away from the gear face by approximately 1 mm. I tested the fit by giving the raceway a bump towards the gear face using a pin punch and soft faced hammer but it won't move, suspect it is still tight, similar to what John Z. has reported. This is assuming that the needle roller inner race was originally butted up to the gear face. Does anyone have a drawing of the pin wrench required for dismantling the pinion assembly ?
 

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K100Dennis said:
Does anyone have a drawing of the pin wrench required for dismantling the pinion assembly ?
Dennis,

This is what I use. The pins are not full width on the slots but I have done several pinions with it and no issues. W1271 Spindle tool and I picked it up at a local autoparts house.

I believe Curtis used the same one but welded additional material on the pins. Your choice.
 

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Discussion Starter #18
jzeiler said:
Dennis,

This is what I use. The pins are not full width on the slots but I have done several pinions with it and no issues. W1271 Spindle tool and I picked it up at a local autoparts house.

I believe Curtis used the same one but welded additional material on the pins. Your choice.
Yes, that's the exact tool I found at a local autoparts store. I found that by building up the outer surface of the pins and the body of the tool adjacent to the pins by welding, and then trimming on the bench grinder. I found this made the pins engage more securely, fits snugly in the final drive housing and will stay engaged without having to hold it in place. However, as John notes, the tool will work as is.
 
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