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68 AMX differential service requirements

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John1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John1 Quote  Post ReplyReply Direct Link To This Post Topic: 68 AMX differential service requirements
    Posted: Apr/05/2021 at 11:16pm
So doing a restoration on my 1968 AMX 290 4sp with 53,000 miles on it and I will shortly be coming to the differential. Likely 3:54 gears, I'm guessing that's what AMC would have put on a base AMX - non TG. I'll be putting in a parts order shortly and wanted to know what to include.

I'm wondering what is in store, has been sitting for decades, haven't popped the cover to have a look yet.
I'm assuming the seals are dry and grease is toast.
I'm hoping all I'm looking at is new inner and outer axle seals, repack the wheel bearings, new pinion seal and hopefully that's it.
Should I be replacing the wheel bearings as well? I notice the TSM specifies a new pinion nut so I guess I'll replace this as well.
I also see the TSM also specifies some tools for the pinion. (I have a hub puller)
Can I get away with finding a way to bind the axles while I turn the yoke and pinion nut or do I stand a chance of damage?
I'm hoping that I don't have to deal with end play etc. or would I have to deal with this if I require new bearings?
Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1948kaiser Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 2:03pm
on the outer seals behind the hub after pulling out the axes. DO NOT use a claw seal puller it will tear up the inside of the housing. instead after ever thing is out of the housing axels pinion etc use a round wooden dowel put into the housing and push out the seals from the inside. very quick and not scoring the housing inside.
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John1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 8:55pm
I was hoping I wouldn't have to pull the whole works apart to do the seals and pack the axle bearings. The TSM doesn't specify a puller and neither does it indicate that you must remove the carrier to do the seals. This sounds like a lot more work than I was expecting. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 10:24pm
You can change axle bearings and seals without touching the ring and pinion. No need to touch the cover or drain oil even.

I disagree on pulling that inner seal, it's easy to do without harm. I don't have a tool, I cut a rectangle of scrap metal with a hole in the center, small enough to pass through the hole and large enough to toggle inside. With a few inches of threaded rod and a nut, and similar on the outside end, it makes a decent puller. Just lever off the open housing end.

I've not used a claw-type puller before, can't they be set to just fit inside the seal hole? Why do they necessarily gouge the housing? Which would be bad I agree.

I cannot recall how I've inserted the seals. It's not a big deal. Sealer and I probably use a short length of something like tailpipe (thin wall tube). Doesn't require a lot of force, tap and go slow.

Rear axles seem so grossly overbuilt -- for the sixes anyway -- that I have not once had tro service ring and pinion or internal bearings on multiple axles well over 200K on them. Hubs, SET6, inner and outer seals last about 20 years.

1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
1968 American, 199ci, T14
AMC pages: http://www.sr-ix.com/AMC/

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tomj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 10:27pm
I woudl assume old bearings and seals are bad.  It's so invasive to take the axles out, hubs off, etc there's no savings in not buying new parts. Don't use NOS seals, they're all junk too old. Even "new" ones at this point are old enough.


1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
1968 American, 199ci, T14
AMC pages: http://www.sr-ix.com/AMC/

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John1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 11:18pm
Sounds like good advise. Probably not great for the bearings to have the weight of a car sitting in one spot for decades. Guess I'll have to trundle off to a machine shop to get the bearings pressed off and on. I'm hoping the bearings in the carrier should be fine even though they sat for decades. I'll know more when I pull the diff from out under the car. I'll watch my method of seal pulling to avoid damage. Was thinking I'd use a piece of PVC pipe to seat the seals. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Apr/07/2021 at 1:50am
I have many AMC's that sat for decades with axles that function perfectly after a fluid change and new wheel bearings. 

With only 54,000 miles, I doubt anything needs replaced, even the wheel bearings. I'd still pull the axle shafts out to clean and repack the wheel bearings since the original grease has likely turned into peanut butter by now. Cleaning that stuff out and repacking with new grease will let those old bearings run for a very long time. Of course I'd change the gear case oil too. 

AMC axles typically do not require an overhaul until at least 150,000 miles in my experience. They were very high quality units dating back to the days before Pearl Harbor. 
'66 Marlin: 327/T10/3.54
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador Brougham: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'82 Concord D/L: 258/TF998/2.35
'84 Eagle Limited: 258/TF998/2.35
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John1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/07/2021 at 10:46am
Overall that had been my experience back when I was playing with them. The AMX that I had rescued had a noisy rear end, which I swapped out for a 3.31 TG that I had with well over 100K mi on it, that I put behind a 390. No Issues. I think I'll keep all of the advise here in mind and do a very careful inspection of the components. if in doubt, chuck it out :)  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Apr/07/2021 at 1:55pm
I would personally change gear oil and give it a try.  If you are going to do a full restoration, remove all the parts, sandblast...  they yeah, go the full route.    If you are going to take it on a thousand mile trip, then it's probably also worth tear down right away.  But otherwise, I'd start simple.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/07/2021 at 3:06pm
Tempting. I'm not going concours as it's only a 290 4sp with absolutely no options on it. These cars love to drive so no trailer queen for this one. Ordered heavy springs and have urethane bushings for it, planning on radials KYB shocks etc. so putting it together to handle. Hopefully the ride won't be too harsh, had everything but the urethane bushings last time and it was alright.  But only 53,000 miles and I'm the second owner (on paper anyway) Interior complete and undamaged, no alterations, original air guard etc. I'm trying to keep it original. Salt from running on the highway through the Canadian Prairies have done a number on the diff, drive shaft, front end components etc, so I don't think they'll ever look smooth, but overall the body is pretty good considering. 
I'm going to start pulling the front end apart in the next week or so and looking at the front bearings should give me some insight on what the rear is like. Tempted to just pop the cover take a peak, new gasket, refill with some At 209 put in to soften gaskets and give it a try ;) But might be wishful thinking that the grease hasn't turned to peanut butter as mentioned on this thread or the seals won't leak like a sieve. 
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