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AMC20 Axel Reassembly

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Bruce Clarkson View Drop Down
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    Posted: Jan/02/2018 at 11:25am
I've successfully pulled the axles out of my 67 Ambassador. The hubs are off and the splines look fine. I'm about ready to put them back in along with new seals and bearings. And I've read the TSM but have never done this before.

Inside of the outer seal there is the brake support plate (that all the other break stuff gets attached to), and several shims (left side) and then finally the axle tube itself. I see no mention in the TSM about any sealant in these surfaces. What advice to you more experienced folks have about this? What sealant goes where?

And, since this is the first time for this, any other sage wisdom unique to reassembling these axles is appreciated

Bruce Clarkson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/02/2018 at 12:00pm
No sealant required. Won't hurt to use a very light coat of RTV on the outer diameter when you put the seal in, but make sure surfaces are CLEAN (wipe with paint thinner or alcohol, or spray brake cleaner) first.

The hub nut should be torqued to 250 ft/lbs. There is also a stick-out measurement for the hub. Might take more than 250 ft/lbs to get the measurement right. I never worried about the measurement, and the TSM says to check the measurement only when putting a new hub on. When reusing your old hubs (make sure you have the hub on the SAME axle it came from!) you should just tighten the nut to 250 ft/lbs.

A new hub is a different story (not that you can get a new one any more!). New hubs are smooth inside, no splines. The splines are created when the hub is installed on the axle, as the hub material is slightly softer than the hardened axle. If you don't get it down to that measurement (which should take more than 250 ft/lbs) you may not form the splines deep enough. Most miss that the measurement is for NEW hubs, not old! Old ones should have the correct spline depth, just tighten the nut to 250 ft/lbs. After the measurement is reached with new hubs the nut should be loosened then torqued to 250 ft/lbs as well.

One more note -- NEVER swap hubs from side to side or from a used axle. If you spin a hub (which you won't do if axle nut it torqued right unless you're drag racing with sticky tires and good traction control)you must either use a new hub or change the entire axle/hub form another rear end. Hubs and axles mate for life.... Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vinny Quote  Post ReplyReply Direct Link To This Post Posted: Jan/02/2018 at 1:32pm
I think the shims are for axle free end play which IIRC should be from .004" to .008" as you probably found out from the TSM. I would think that with the old bearings the free play might be more than what is recommended but with the new bearings probably within spec.

What's your axle diameter, 1 3/8"?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce Clarkson Quote  Post ReplyReply Direct Link To This Post Posted: Jan/02/2018 at 5:56pm
Thanks!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/02/2018 at 6:15pm
Shims for axle end play - LEFT side only - meaning don't use any shims on the other side
I use a thin (meaning thin) layer of RTV on the parts because they are not longer clean, perfect and flat like they were from the factory. (unless you found clean NOS shims, and file the ends of the axle tubes (the flanges) flat, etc.)
Be sure that drain hole is CLEAR and the shield is put on properly. That's made so that if the seal leaks the lube will drain out the back side and not get to the brakes.
Be really sure to pay attention to the TSM axle to hub depth setting - It explains how to pull the hub onto the axle and measure the end of the axle sticking out from the hub.
Follow it to the letter and you will not have issues.
I've been doing AMC axles since the 1970s and have never had one fail on my own or any customer car (and the boss had me doing a lot of that sort of thing because it was heavy and dirty LOL)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce Clarkson Quote  Post ReplyReply Direct Link To This Post Posted: Jan/02/2018 at 8:33pm
Thanks. And yes, it was dirty.

I did not know about a drain. I'll look first thing in the morning. Thanks.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/02/2018 at 8:53pm
The shield that is the last thing on in these photos - held on with the four nuts, has sort of a funnel shape at the bottom. In the backing plate there is a hole. Lube that leaks out to this point should gather in or be stopped by this shield and be guided out the back of the backing plate through the hole just below the axle.
In the bottom picture (this is a model 20) you can see the hole I refer to just to the right of the dial indicator clamp.
If you use sealer, make sure this hole stays open. The bottom of the shield is sort of funnel shaped.

(In the bottom picture I'm checking axle end-play) 




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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce Clarkson Quote  Post ReplyReply Direct Link To This Post Posted: Jan/03/2018 at 11:04pm
Thanks for the info and great pix.

I just put mine back together today and with the help of your explanation I see what you mean. Mine had worked some but was a bit clogged up with grime from the combination of lube and brake dust that had gathered over quite a few miles. It's all cleaned up now (everything except the residual in places on my hands :) ) and hopefully neither side will leak.

For anyone else doing this, I was surprised by the end play. I had slightly excessive end play with my very old bearings. I put the shims back just like I found them with only the thinnest of coatings of Permatex 3 at the end of the axle tube and the end play has worked out great. I'm no bearing expert but perhaps my slight excess of end play was from worn bearings? Or maybe just variations in parts? Dunno. Anyhow, if I would have tried to fix the end play based on measurements from the old bearings I probably would have made a mistake.

Thanks again for the info,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/04/2018 at 7:18am
More than likely from worn bearings. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jan/04/2018 at 5:15pm
I'd concur - there are other possibilities, but remote, and without knowing details, I'll stick with "what he said".
think about it - if you have only .003" wear on each surface times the number of surfaces (inner bearing surface, cup/race surface, roller surfaces) times the number of bearings (one per side) that's a fair stack-up.
These things are decades old, after-all........

As long as you have the right parts in the right order and the end-play is in specs........ you should be good to go. 
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