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AMC 20 advise repair? replace?

bobbysjeep

bobbysjeep

Legacy Registered User
City
Charlotte
State
NC
^advice^

Well feeling pretty bummed. I have been suspecting that I had a busted 2pc axle. It started chattering and slipping under heavy takeoff acceleration. I pulled the driver side axle and sure enough it was sheared from the hub. So I bought a driver side axle, gear oil, and diff gasket. Pulled the cover to clean and inspect. Found that one of my TracLoc spider gears is damaged. A new unit is way too expensive, I have no experience rebuilding, repairing diffs. I do not off-road or do any aggressive driving, so I'm not interested in upgrading to a locker, one pc axles or even changing from 3.31 gears. If I find a used tracLoc unit does everything have to be re-shimmed/backlash setup again? Expensive? Should I just try to find another rear-end with 3.31 gears? Thoughts?

BTW.... Best that I can tell the ring and pinion gears are okay.

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Bobby I'm having the exact same issue. I'm already $1100 lighter from a butcher shop so I'm all ears here fellas on a good fix.
 
I do the same type of driving as Bobby and the same type of experience. My axle looked that same way at the shop. We tried the two piece axle fix but the tech couldn't make it work. I still have the new hub. We used the new axle and my old hub. Two months later and $1100 lighter here I sit.
 
If you put a whole nother carrier in there the gears will have to be set up again, but can't you simply get new spider gears and install in that carrier? I know when replacing spider gears with a lunchbox locker you don't have to reset up the ring and pinion, so don't know why the same wouldn't hold true with just putting new spider gears in your existing carrier.

I bet someone here has spider gears they took out to add a locker. Are trac lock and open diff spider gears the same?
 
Thanks for the replys so far! So I have been researching just removing the tracloc carrier unit and replacing spider gears and clutch packs. From what I understand, if I mark everything and reinstall exactly, in theory I should be ok. Does anyone have experince just replacing spider gears and reinstalling gears, bearings, etc? Still weighing cost of repair vs used axle, but leaning toward repair if I don't have to set gears.
 
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The tracloc carrier and the open differential carrier are different
Look in the quadratec magazine, I believe you can buy all the parts
 
bobbysjeep said:
Thanks for the replys so far! So I have been researching just removing the tracloc carrier unit and replacing spider gears and clutch packs. From what I understand, if I mark everything and reinstall exactly, in theory I should be ok. Does anyone have experince just replacing spider gears and reinstalling gears, bearings, etc? Still weighing cost of repair vs used axle, but leaning toward repair if I don't have to set gears.
Click to expand...

I "accidentally" did this awhile back when installing 1 piece axles in my Green Scrambler, that has a Trac Loc:thumbsup:

YES, you can pull it apart and back together, no problem.

1) Pull both axles
2) Remove the carrier bearing caps, mark them, so they go on exactly as they came off (side to side, top and bottom)
3) Remove ring gear from carrier (again, mark the ring gear/carrier so you put it back together the same way
4) You can then pull apart the clutches/spider gears. Go slow, it will fall apart in a big pile

Pretty easy, follow the FSM, especially when reassembling the clutch packs.
Make sure to add the additive to the new gear oil, or it will chatter/stick:twocents:

On a AMC20, the shims are inboard of the carrier bearings, no need to pull carrier bearings, so no need to worry about R&P settings.
If installing one piece axles with a TracLok, you "might" have to remove the thrust block, I did.
 
IMHO wouldn't run that axle again without a complete rebuild. How long was that gear in there broken? How many metal pieces from it have circulated through your bearings/seals in the gear oil (could be too small for you to see and still do damage)? Seems like a lot of work to go through without replacing bearings that may have eaten a fair bit of metal, you could be back into the rear axle before long.

I'm reading your post as you were running with the broken gear for some time before you addressed the axle when the two-piece axle let loose, right? So that's possibly to likely unrelated to when the gear broke.

One other thing to keep in mind: traction is NOT a friend of 2-piece axles. One of the worst situations for those is when you're ON road, with full traction, and you have to goose the gas for some reason.

Sure they let loose when people beat on them on the trail, but there's been a LOT of stories of them going pulling out of a parking lot or some such thing. From what you've said here, yours apparently let go on the road, right?

Do not assume one-piece axles are for folks who offroad only. Once one went, I would have stepped up to one-pieces or looked for a good used axle with them already, just to avoid having to get back into this.

Just my :twocents:
 
Thanks for the info spankrjs. Also, I noticed that you said easy... Easy for you is not easy for all! But I have the FSM and found some good how-to stuff online.


BW, Thanks for sharing your thoughts and experience.

So, hindsight/history... My nephew asked to drive my Jeep some time back, unbeknownst to me he had never driven a stick! What does he do? Rev the engine and dump the clutch (on dry pavement) we hear a load pop.

When I have sheared 2pc axles in the past while wheeling, the Jeep was disabled instantly. This time possibly due to the trak-lok and the axle taper press fit, and my driving style no issues surfaced initially. Even towed my light aluminum boat on several occasions with no issues.

Then one day while in 4H i heard a loud pop pop. My theory is that the spider broke then, and was related to the broke axle play. Also, been reading that broken spider gears is a common issue that plagued early Traclok LS in AMC 20, so I'm not positive that they are related.

When I removed the cover there where 2 big chunks of the damaged tooth. I have not removed or rotated anything to see the extent of the damage. I'm hoping it is just the one tooth, and it fell to the bottom of the housing and no other gears were affected... The oil looked pretty good with some typical sediment in the bottom.

What I am going to do before I spent another penny is remove the other axle, pull the trac-lok carrier/ring gear, and carrier bearings. This will allow me to clean everything up and look everything over really good. Once I inspect then I can decide on repair vs replace. Hopefully no other damage was done.

Thanks again and I'll let you know what I find.
 
I don't know that I believe that it would be possible for a Traclok that old to make the Jeep work anything even close to normally at normal driving speeds with a sheared 2-piece hub on one end. Towing? :shrug: I think the gear teeth let go first.

You have a good plan, regardless.
 
If none of the ring and pinion teeth are damaged, and the carrier/pinion rotate smoothly, bearings might be fine:twocents:

But, like BigWalton said, might not be a bad idea to change the carrier and pinion bearings, especially if it rotates rough or has a bunch of miles. If you keep track of all the shims, you can just change the bearings, no need to set back up the gears:twocents:

On my mostly stock green Scrambler, the differential centering block wore, allowing the axles to plunge inward slightly, enough to leak oil at the outer seals. I originally just changed the seals and bearings on the axles, only to have the leak show back up:banghead: I went ahead and swapped in Moser axles, and then discovered I had to remove the centering block when the second axle would not slide in all the way:crazy:

As for the Trak-Locs performace, it is no Detrioit locker, but on my green Scrambler with 30" street tires, it will spin one tire on concrete while the other is spinning in gravel:smokin: Big tires and rocks, not so much:rotfl:
 
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bigwalton said:
When 30 years old or after rebuild though? The traclok in the Postal's stock axle was an open diff.
Click to expand...

On mine, 120,000+ miles, no rebuild by me, I was surprised:eek:

The clutches on mine still had the raised ridges, everything was good. I cant be sure if the previous owner messed with it, though, but the rest of the rear axle looked original, down to the Torx bolts holding the cover on, and the red dirt in the axle tubes:shrug:

When I first put it back together and drove it, after filling with 90 weight that said it had LSD additive, it jerked and banged like a Detroit. I had to buy the Jeep Trac-Lok additive from the dealer to get it back smooth. But, it is still only a LSD:thumbsup:

When Tommy first got his white Jamboree, it was in 4 Low. When we put it in 2wd, it wouldn't go anywhere, just make horrible sounds. On this CJ with a Trac-Lok, the spun axle on one side resulted in no wheel drive, so I've seen it both ways:shrug:
 
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Good information, just what I was looking for.

As far as what failed when, it's just my theory. I have driven it a few hundred mile in it's current condition (slipping only occasionally) but most the time I would just baby it. It gradually started slipping worse and worse. Last week when pulling up my short steep driveway into the garage it was bad. That's when I decided to quit putting this off.

Look at the axle where the bearing race should be pressed on. It's hard to tell but it's a good 1/16th smaller than it should be. The bearing apparently seized and spun on the axle over some time. Also, there is no sign of a keyway slot, the axle end has been chewed away. Over the summer I noticed the tire looked bad out of balance. So I think the LS has been keeping me moving until recently. Now its probably wore-out. The Jeep has 125,000 miles and I don't believe the diff cover had ever been removed. It did not have a trace of sealant, just an old cork gasket. Again just my best guess.

I measured the axle tube housing and it is still good, the bearing stayed put on the OD. The moral of the story, don't procrastinate when stuff breaks!

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