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amc 20 hubs

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jeanbonjeanbon1 View Drop Down
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    Posted: Nov/13/2018 at 7:25am
I noticed that the hub was the weak point on an amc 20 rear end.
I'll put the hubs back on,later this week, and was wondering if anybody ever tried to put some green locktite on the splines to seized the hubs on the shafts after a rebuilt. I think it would give more strenght to the assembly and could still be removed with heat .
anybody ever tried this out ????????Geek

Regards,Jean
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2018 at 7:34am
Originally posted by jeanbonjeanbon1 jeanbonjeanbon1 wrote:

I noticed that the hub was the weak point on an amc 20 rear end.
I'll put the hubs back on,later <span style="font-size: 0.75em;">this week, and was wondering if anybody ever tried to put some green locktite on the splines to seized the hubs on the shafts after a rebuilt. I think it would give more strenght to the assembly and could still be removed with heat .</span>
anybody ever tried this out ????????Geek



Simple maintenance will do, since you cannot ignore doing so, loctite won't make a difference when retightening, since it will change the bond, and may break away leaving you with no added protection after maintenance.

If concerned, adding a keyway to help, like shown in performance American style, will help, but again maintenance routine is critical.

One thing to note, with twin grip, one side will always lock down the nut, and the other will loosen. It Is a tough mug to break loose the tight one, but always good to check it anyway.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2018 at 2:23pm
The hubs are keyed, splined, and tapered to the shafts and held by a nut tightened to more than 250 foot pounds that is cotter pinned into place. I think you've be hard-pressed to break them.

I drove my Marlin around for a couple years not knowing that the nut was barely snug and cotter pinned in place that way. I did several 1st gear dump clutch operations with a V8 making 365 foot-pounds of torque through a 2.43 first gear ratio and a 3.54 ring and pinion ratio. It and never sheared a shaft or damaged anything. Pissed off the tires but didn't hurt the axle. And that's in a 3500 pound family car, not a little Javelin or AMX. Yes, they are properly tightened now. 

You should see the way the Jeep guys beat their AMC 20's off road and don't break them. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2018 at 4:56pm
Unless you plan on putting some crazy power to it the axle will be fine. I broke one at the dragstrip back in 2004. It didn't turn the splines in the hub, the axle actually snapped just behind the taper. The splined section of the axle was still in the hub after it broke.

-Steve-

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeanbonjeanbon1 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2018 at 6:06pm
As always, expert answers from the forum members. I won't put any locktite on the splines as i don't intend to drag the car in any ways and you comforted in the strenght of the assmbly. 
thank you all for your time 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/16/2018 at 5:40am
250 ft/lbs is the factory spec. Don't go over 300. Tighter isn't necessarily better, as it can induce added strain on the part, but 300 isn't too much. The axle end stretches every so slightly over the years. My speculation is that AMC never recommended re-torquing the axles because they were easily good for 10 year/100K+ miles. That was basically the designed life of the car. Keep it much longer and you have to change the rear axle bearings or seals anyway, they will get re-torqued when reassembled.

Flash forward 50 or so years. A couple years ago at least three people posted about spun hubs -- all 58-63 Classics with 196 sixes! So no big power, but bearings or seals had never been changed in any. One had under 100K miles on it, around 75=80K IIRC, the others had a bit over 100K. TIME was the main issue. They were driven normally for an old car, not horsed around with. There's only so much you can do in a big car with a small low power six!

The moral to this is if you re-torque the axle nuts every 15 years or so you shouldn't have a problem UNLESS you have over 400 hp and drag racing a lot. An occasional fun trip down the strip on street tires won't hurt a thing. Hard launches on slicks with a good hook-up and high power can be an issue, especially in the bigger, heavier cars. A know a couple people with AMX drag cars that use 7" or 8" slicks and have always run the stock axles with around 400-450 hp. No problems, but one did admit to re-torquing the axles nuts at the beginning of every season.

The nuts need to be loosened then torqued back down. They can be stuck and require 500 ft/lbs or more to get moving again, but stuck isn't the same as torqued!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/17/2018 at 11:35pm
i'm with frank on this. i spun a hub (passenger side) on my 63 classic wagon pulling gently out of a metered parking spot. long story short, i bought a used axle and hub and proceeded to do exactly what you're not supposed to do -- but have no choice today -- and put a used hub on the old axle (which was OK). i LOCTITE'd it and torqued it and drove it another few years til i sold it.

there's no way to know if re-torquing would have fixed it for sure, but it seems very likely. i dont recall if the old hub was noticably loose. i agree with frank also, 30, 40, 50 years is waaaay past expected design life, no blame on AMC for not forseeing this.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeanbonjeanbon1 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2018 at 6:14am
The nuts need to be loosened then torqued back down. They can be stuck and require 500 ft/lbs or more
 to get moving again, but stuck isn't the same as torqued!

I agree with you as stuck ain't torque as evtg on the car is now beeing retorqued as per tsm and might
check the torque on this particular nut every now and then LOL


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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2018 at 7:59am
Some of the CJ guys have had spun hubs and not even known it at first,

if you have a locker, the other axle will drive you around fine....  for a short while LOL

I seem to recall a buddy with 2 piece axles, a Lock-Right (drop in "lunchbox locker") and 32" tires saying his Jeep was pulling to one side,
then the next day or so the brake on that side locked up.

The story that scared me away from the 2-piece shafts was a magazine article testing a 71, or 72 Javelin,
wheel fell off right at a traffic light.

The whole article read like a hit piece anyway,
but having a wheel fall off could have tainted the writers perspective ConfusedLOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2018 at 9:05am
I did lose a hub on my Jeep CJ.  Like jpnjim said, lockers, 4.27 gears, and 36" tires all contributed.  I was probably way beyond what AMC ever designed the axle to support.  Spun the right side, and the pressure against the nut sheared the cotter key and spun the nut right off the axle.  Lost a rear tire/hub/drum right on the trail.  The nut was still in the cap, so we threaded it back on and limped home (only about 10 miles).  Went to one piece axles an never looked back. 

I still have the 2 piece axles in my AMX.  I did loosen and re-torque during the rebuild.  Running the factory twin grip and 26" Michelin Pilot tires.  Runs 13.5s at the drag strip, never any problems.

Bob
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