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Mike Anhalt

Gear box problem LI150

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I've always been aware that this could happen but had never actually seen it until recently.

 

Early Spanish LI150 gear box with matching drive axle. When the 4 loose gears are installed there is less than .001" height difference between the gears and the axle. According to Stickys there should be about .003" (.02mm) difference between the two, with the gears being on the taller side. If the 2 parts are in line or the axle is taller it is impossible to shim the gears correctly.

 

I took the axle and gears to a local machine shop and they suggested the axle be ground down a couple .001" to drop below the gears.

 

 

Does this sound like a plausible/correct fix? The problem is with the gears them selves. I suspect they are machined wrong from the factory.

 

I can't change the gear stack because that's what the customer wants.

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It's early, like Italian but I have a second one in a busted up motor that I need to extract first. If neither work I might be hitting you up. I'd really like to figure out a correct fix if possible.

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Can you try other gear stacks and axles, just to compare? If the gear stack is shorter than it needs to be, the axle will have to be ground to make it work correctly. If the axle was made too long, the axle will still need to be ground down, or replaced. Personally though, I would want to know which part is the incorrect part before I go doing that. I suppose even a rear hub bearing could cause that couldn't it? Since the axle sit against it.

 

I would just very carefully measure everything against some other known good parts before making an irreversible machining operation. It should work though. Especially if you only need a few thou.

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Can you try other gear stacks and axles, just to compare? If the gear stack is shorter than it needs to be, the axle will have to be ground to make it work correctly. If the axle was made too long, the axle will still need to be ground down, or replaced. Personally though, I would want to know which part is the incorrect part before I go doing that. I suppose even a rear hub bearing could cause that couldn't it? Since the axle sit against it.

 

I would just very carefully measure everything against some other known good parts before making an irreversible machining operation. It should work though. Especially if you only need a few thou.

I'm in the process of measuring everything out and have a couple of other gear boxes to compare with. No spare drive axles though :(

The rear main bearing has no bearing (pun intended) on the gear height relative to the axle its self, only in relation to the endplate and over all gear stack height (if that makes sense). Right now I have the loose axle and loose gears on the bench for the measuring and hope to have a simple solution. The gear stack is really only .003" too short compared to the axle, so that's got to be less than .0005" under on each side of each gear.

I agree with you, I don't want to make a one way change that can cause problems down the road if the gear box gets changed. On the plus side there is a shop here that sharpens and makes machine tools. I'm checking with them this week to see if they can grind the axle end down a couple thou.

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The rear main bearing has no bearing (pun intended) on the gear height relative to the axle its self, only in relation to the endplate and over all gear stack height (if that makes sense). Right now I have the loose axle and loose gears on the bench for the measuring and hope to have a simple solution. The gear stack is really only .003" too short compared to the axle, so that's got to be less than .0005" under on each side of each gear.

 

 

Yup, that is correct. I thought about that wrong. But the stop on the axle that 4th gear sits against could be machined too deep, allowing the whole stack to sit low I suppose. I have a few axles here, but several are suspect. There's a genuine TV200 one here though :D . I'm sure we can get some measurements for you if needed. 

 

As you said with only being a half thou each side of the gears, you suppose maybe the gears are just a bit worn? Maybe it was run with old/low oil at some point? 

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Yup, that is correct. I thought about that wrong. But the stop on the axle that 4th gear sits against could be machined too deep, allowing the whole stack to sit low I suppose. I have a few axles here, but several are suspect. There's a genuine TV200 one here though :D . I'm sure we can get some measurements for you if needed. 

 

As you said with only being a half thou each side of the gears, you suppose maybe the gears are just a bit worn? Maybe it was run with old/low oil at some point? 

 

I really think it's in the gears. The shift spider lines up perfect in 4th relative to the lip on the axle.

 

This motor had a hard life, I wouldn't be surprised at all if it was subject to the no oil treatment for a few thousand miles. Plus being Serveta, they were never shimmed correctly to start with (not that that makes them bad or anything).

 

So yeah, photos, write up and all that getting put together this week.

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