Speedo Gear Rubbing on Hub

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B

Bonwit

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I must have left a part out 'cause shortly after reassembling my rear wheel I noticed my speedo gear box had slung grease all over my hub and wheel. Upon removal, I noticed the hub disk was galled where it had contacted the speedo gear case. It appears the rubbing heated things up, melting the grease and thus the mess.

I'm guessing there should be some sort of spacer or washer to hold the gearbox away from the hub cap, but looking at the parts manual, I don't see anything between the gearbox and the lockring (#27). BTW, I'm missing spacer NM.13270 (#34). Is that the problem? At first, I thought it was just a washer, but looking at the diagram, it appears different, more like a bushing. What am I missing here?

Thanks!

Speedo Gear Rubbing on Hub
 
There is a spacer under the speedo drive, the id is the spindle od and there are 2 OD,s, looks like part 23 lower down on the parts sheet. Why is not listed I don;t understand as its also missing from the 74 850 one too. There are soft ones around that get squashed and give the symptoms you have. You just need a part number but I can't find one.
 
There is an extended thread on this issue, I am sure a search on gearbox and grease will find it. Some find just replacing item 34 fixes the problem, but your gearbox should not contact the cover plate.

Dave
69S
 
And it goes on before the speedo drive not after it in the parts diagram, thats what made me miss it.
 
So is part 34, the top hat spacer, supposed to fit *inside* the speedo gearbox not outside as shown on the parts list?

Mine rubs also and that might explain it. I've been looking at the parts trying to figure out what's wrong. I had everything assembled as shown in the diagram but obviously something was wrong somewhere.

Debby
 
Here is a picture of the item 34 that is in the gearbox partially pushed out of it. Apparently they get crushed after several rear wheel assemblies and they either need replacement or a shim placed under them next to the hub bearing nut so the gearbox clears the wheel cover. I think I used a 1" socket to punch it out of the gearbox, it was not apparent that it would come out, when you look at it, it looks like it is just part of the gearbox, but it does come out.

Speedo Gear Rubbing on Hub


Dave
69S
 
Yeah, that's how mine are installed but I don't see how that does anything to space the speedo gearbox away from the hub. Seems to me you need a shim on the inside of the gearbox, not the outside. I can see how this spacer will center the gearbox radially, but as far as I can tell it does nothing for the gearbox's axial position.

Am I missing something? I don't get it. :?

Debby
 
Debby, hi. I have to believe that that little high hat spacer makes contact with the next part in from the gearbox - #27 in the diagram - thus insulating the gearbox from the stress that tightening the axle imparts, which is transmitted instead through the spacer to part #27. I.e., parts 34 (the high hat spacer) and 27 are stressed by tightening the axle, but the gearbox is not.

Could be wrong, I'm no mechanical engineer (to say the least...!)
 
Deb, that is my understanding also.
I must have lost the spacer washer in mine during a rebuild years ago, ended up just taking the speedo and cable off entirely.
Always bothered me, the possibility of the gearbox snagging, needing grease, cable lube.
Life is good with just the tach!
 
#27 is the bearing lockring. I don't think the spacer should be contacting that. The only thing making contact with it should be the drive ring in the gearbox.

It looks to me like the intent is for the #34 spacer to contact the end of the bearing spacer, #29 in the diagram, to prevent the gearbox housing from being crushed. Mine does not even come close, and that includes new (Andover) ones that certainly are not crushed. I'll have to post some photos...

Debby
 
Debby, now that I look at the whole diagram (courtesy of Old Britts) I think you may be right that the high hat spacer hits part 29 instead of 27. But I do believe that the basic point that this spacer takes the stress of axle-tightening in lieu of the gearbox doing so is correct. If yours doesn't, I have to believe something's amiss?
 
Thanks for all the replies. Well I guess I do have the top hat spacer after all. Problem is, while hammering it out, the retention ring which is riveted to the case turned loose! I think my gearbox is toast. :cry: I'm still puzzled how this spacer would keep the gearbox clear of the hub. I can see no damage to it, though the hole in the case itself is a bit mushroomed on the inside. Something's not right!
 
Yes, the item 34 does contact the hub spacer, item 29, however the thickness of the tophat spacer (34) is pretty thin and can be crushed or worn down after time and either needs replacement or a shim between 29 and 34. That should take care of it. Object is to NOT have the spedobox contact the hub cover. I don't think the dogs in the spedobox should press on the hub nut to any appreciable amount, just engage, and that is another item to install carefully and correctly.

Dave
69S
 
BrianK said:
I think you may be right that the high hat spacer hits part 29 instead of 27. But I do believe that the basic point that this spacer takes the stress of axle-tightening in lieu of the gearbox doing so is correct.
Click to expand...
No, the top hat #34 slips inside #29 and offers no spacing that I can see. It looks like there should be another spacer or washer that is not shown in the parts diagram.
 
OK, yes 34 does slip inside 29, but it is still a washer between the hub and the spedobox. If you need to space the spedo box out more, it looks like the inside dia. of the washer needs to be about 0.675" and a max od. of 1". I would think space it out enough so it does not contact the hub cover, but the dogs in the spedo box make solid connections with the hub nut.

Speedo Gear Rubbing on Hub


Dave
69S
 
Man, where do you guys find all these great pics???

Thanks much! I am always willing - hell, thrilled! - to be educated.
 
Brian,

I just now made it, I happen to have everything apart.

Dave
69S
 
so now to attempt a repair. Anyone think a few #40 aircraft rivets will hold this inner ring in place?
 
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