mjtjnj Posted October 15, 2008 Share Posted October 15, 2008 I found "the last" AMC 20 from an MJ with 4.10 gears on car-parts.com. They made me a good deal, with shipping from WI, but told me it was missing the drums and "rusty." I told them as long as it turned, and wasn't rusted THROUGH, that was fine. It's not rusted through, looks straight, but there's a good amount of slop when I spin the yoke by hand. OK, so it's well-worn. My real concern was that the left axle doesn't spin. I didn't really try HARD, but it's frozen. When I spin the yoke, only the right axle spins. I'm going to try to use a breaker bar or something to free up the left one. I was hoping to buy this, sandblast, paint, new brakes/drums and go. I'm hoping I don't have to rebuild the whole thing on top of it. Is the frozen left side something to be concerned about? Thanks Tom Link to comment Share on other sites More sharing options...
BLHTAZ Posted October 15, 2008 Share Posted October 15, 2008 If you can turn the right side via the pinion, it's likely that the wheel bearing is siezed up. I would try to pull the shaft out and see what's up. Hopefully it's not frozen to the shaft. Link to comment Share on other sites More sharing options...
pingpong Posted October 15, 2008 Share Posted October 15, 2008 I would definately look at rebuilding the whole axle, especially given your current symptom. Keep in mind some new axle kits include bearings and all the associated stuff. I know it was cheaper for me to swap Chromo's in then it would have been to buy everything piece meal Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted October 15, 2008 Share Posted October 15, 2008 I agree, just re-build it now before the install. Good find too!! CW Link to comment Share on other sites More sharing options...
mjtjnj Posted October 16, 2008 Author Share Posted October 16, 2008 I would definately look at rebuilding the whole axle, especially given your current symptom. Keep in mind some new axle kits include bearings and all the associated stuff. I know it was cheaper for me to swap Chromo's in then it would have been to buy everything piece meal Yeah, that makes sense. What axle kit/supplier do you recommend? Maybe I'll make it posi while I'm at it Link to comment Share on other sites More sharing options...
pingpong Posted October 16, 2008 Share Posted October 16, 2008 I prefer Alloy USA. I don't know if they make a kit for the MJ amc 20. When you order make sure you get the right kit. The amc 20 came under a few different rigs, and they were different widths. My kit for my XJ d44 was 260. That including bearings retainer rings, retainer plates, oil seal, lug nuts and wheel studs. You will need acces to a press to install the bearings and retaining ring. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 16, 2008 Author Share Posted October 16, 2008 I prefer Alloy USA. I don't know if they make a kit for the MJ amc 20. When you order make sure you get the right kit. The amc 20 came under a few different rigs, and they were different widths. My kit for my XJ d44 was 260. That including bearings retainer rings, retainer plates, oil seal, lug nuts and wheel studs. You will need acces to a press to install the bearings and retaining ring. http://cgi.ebay.com/ebaymotors/JEEP-AMC-DANA-20-AXLE-MASTER-REBUILD-BEARING-KIT_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el1116QQitemZ110251426205 Would something like this be what I need? This guy says his kit fits all amc20's from 1976 on, is he wrong? If the gears look ok, I should just leave them alone? I don't know the first thing about the guts of differentials, aside from popping off the cover and draining fluid, and changing shafts on my D35. Thanks Tom :popcorn: Link to comment Share on other sites More sharing options...
FxRacing282 Posted October 16, 2008 Share Posted October 16, 2008 I found "the last" AMC 20 from an MJ with 4.10 gears on car-parts.com. They made me a good deal, with shipping from WI, but told me it was missing the drums and "rusty." I told them as long as it turned, and wasn't rusted THROUGH, that was fine. It's not rusted through, looks straight, but there's a good amount of slop when I spin the yoke by hand. OK, so it's well-worn. My real concern was that the left axle doesn't spin. I didn't really try HARD, but it's frozen. When I spin the yoke, only the right axle spins. I'm going to try to use a breaker bar or something to free up the left one. I was hoping to buy this, sandblast, paint, new brakes/drums and go. I'm hoping I don't have to rebuild the whole thing on top of it. Is the frozen left side something to be concerned about? Thanks Tom last year i found an MJ diesel with a AMC20. i never seen that rear end before. so I'm gonna agree with just baout everbody on here. when you rebuilt the rear end. the truck feels better when you drive it. it dosent jerk when you go from coasting to acceleration, its just better. plus there is a fairly good chance its not going to fail for a while. Link to comment Share on other sites More sharing options...
pingpong Posted October 17, 2008 Share Posted October 17, 2008 NO thats not what you need. Thats is for the differential (ring and pinion) what you need are axle bearings, bearing retaining ring, oil seal. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 18, 2008 Share Posted October 18, 2008 last year i found an MJ diesel with a AMC20. i never seen that rear end before. so I'm gonna agree with just baout everbody on here. when you rebuilt the rear end. the truck feels better when you drive it. it dosent jerk when you go from coasting to acceleration, its just better. plus there is a fairly good chance its not going to fail for a while. the MJ diesels had 4.10 or 4.56 gears, and from what I can tell, most or all of the ones in the states (I can only find 15 so far) have AMC20's and the M/T rear springs. testament is my dad's 86 turbo diesel M/T 5 speed 4.10's amc20 rear but base model other than that Link to comment Share on other sites More sharing options...
FxRacing282 Posted October 19, 2008 Share Posted October 19, 2008 last year i found an MJ diesel with a AMC20. i never seen that rear end before. so I'm gonna agree with just baout everbody on here. when you rebuilt the rear end. the truck feels better when you drive it. it dosent jerk when you go from coasting to acceleration, its just better. plus there is a fairly good chance its not going to fail for a while. the MJ diesels had 4.10 or 4.56 gears, and from what I can tell, most or all of the ones in the states (I can only find 15 so far) have AMC20's and the M/T rear springs. testament is my dad's 86 turbo diesel M/T 5 speed 4.10's amc20 rear but base model other than that yes i have only seen one it person. it would be sweeat to own it. it was all black and cad hurricane wheels. but it was also a bit rusty and the bed was rough. havent seen it in 6 months. leaked like a waterfall from every seal Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 19, 2008 Share Posted October 19, 2008 Are you sure the one side was seized? If you spin an open diff axle from the pinion, it will only spin one shaft... If you put a bar on that shaft, it should spin easy enough. Link to comment Share on other sites More sharing options...
FxRacing282 Posted October 19, 2008 Share Posted October 19, 2008 80% or better of axles ive spun always spun both sides. one going one way and the other going another. but i do agree that a bar to free it up is a good idea. if its stuck its time for a fluid swap and maybe some chemicals to clean out some rust or sludge thats making it stick. Link to comment Share on other sites More sharing options...
mjtjnj Posted December 9, 2009 Author Share Posted December 9, 2009 Wow, I've let this axle sit for a year. With the engine problems resolved, I'm going to finally get to this. FYI the MJ AMC20's are the "wide-track" version, same as used in the CJ's. I just got all new brake hardware, wheel cylinders, shoes, drums. Gonna pull the shafts out and replace the wheels bearings. Going to look into that rebuild kit. I bought a rebuilt Trac-Loc for this rear, anyone have a link to installing one? Link to comment Share on other sites More sharing options...
88mjmanche Posted December 9, 2009 Share Posted December 9, 2009 ive got a locker for one of those will sell cheap brand new in box with papers and stuff Link to comment Share on other sites More sharing options...
mjtjnj Posted December 9, 2009 Author Share Posted December 9, 2009 I bought a rebuilt Trac-Loc for this rear... Link to comment Share on other sites More sharing options...
88mjmanche Posted December 9, 2009 Share Posted December 9, 2009 this is a rachet type locker lock right Link to comment Share on other sites More sharing options...
Eagle Posted December 9, 2009 Share Posted December 9, 2009 this is a rachet type locker lock right The stock unit? It's a clutch-type limited slip, not a locker. FYI the MJ AMC20's are the "wide-track" version, same as used in the CJ's. No, the CJ had a 2-piece hub. The hub part is separate, and attatched to the axle shaft with a nut to hold it and a tapered spline to keep it from spinning (in theory). The MJ is a 1-piece axle shaft & hub assembly. Link to comment Share on other sites More sharing options...
mjtjnj Posted December 9, 2009 Author Share Posted December 9, 2009 this is a rachet type locker lock right The stock unit? It's a clutch-type limited slip, not a locker. FYI the MJ AMC20's are the "wide-track" version, same as used in the CJ's. No, the CJ had a 2-piece hub. The hub part is separate, and attatched to the axle shaft with a nut to hold it and a tapered spline to keep it from spinning (in theory). The MJ is a 1-piece axle shaft & hub assembly. You are correct. I had thought the later CJ AMC20 had a one-piece shaft. Same width, still. I may have to get some help installing this LSD; never set up gears before... Tom Link to comment Share on other sites More sharing options...
Pete M Posted December 9, 2009 Share Posted December 9, 2009 I thought widetrack CJs were narrower? :hmm: Link to comment Share on other sites More sharing options...
wallisek Posted December 9, 2009 Share Posted December 9, 2009 That is what I thought but I just took a look at my Yukon gears catalog. The AMC20 for the widetrack CJ7 and the Wagoneer have the same part numbers for the axle shafts. If those two are the same, the MJ has gotta be the same right? :D Link to comment Share on other sites More sharing options...
jpnjim Posted December 9, 2009 Share Posted December 9, 2009 MJ M20's are ~60" wide, with a 5 on 4.5" wheel pattern. FSJ Waggy/NT Cherokee M20 rear's (narrow track) are ~58" & 6 on 5.5" Wide Wheel Cherokee/J10 (wide track) M20's are ~62" & 6 lug. WT CJ's are 54.5" & 5 on 5.5" NT CJ's are 50.5" & 5 on 5.5" I don't know why the Yukon catalog would list the same PN for WT CJ & NT FSJ, but there's atleast a 3" difference in overall axle width, and the wheel bolt patturns are different. Link to comment Share on other sites More sharing options...
wallisek Posted December 9, 2009 Share Posted December 9, 2009 The picture in the catalog shows multiple patterns so my guess is both 5x 5.5 5x ?.? Maybe it isn't an actual picture of said axle shaft. Is it possible it has the same shaft lengths as described in the catalog? Maybe just a wider pumpkin and different length tubes? :hmm: Link to comment Share on other sites More sharing options...
Pete M Posted December 10, 2009 Share Posted December 10, 2009 CJ is 5 on 5.5" SJ is 6 on 5.5" MJ is 5 on 4.5" They share differential guts, but not really anything else. Sorta like what Ford does with the 8.8. Link to comment Share on other sites More sharing options...
akamcbird Posted December 10, 2009 Share Posted December 10, 2009 mjtjnj could you take some measurements from both the amc20 and d35 for the drive shaft thread? center of ujoint to center of axle tube, or just the difference between. thnx http://www.comancheclub.com/forums/viewtopic.php?f=2&t=20131 Link to comment Share on other sites More sharing options...
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