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Model 20 Strength

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scramboy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scramboy Quote  Post ReplyReply Direct Link To This Post Topic: Model 20 Strength
    Posted: Nov/27/2017 at 8:58am
Have a modified model 20 in my Scrambler, Henrys axles, Detroit Locker, welded tubes, super reinforced spring pads, Richmond 4.56 gears, etc. I have a 550+ hp motor going in this winter potentially shooting for 10 sec times. Will the mentioned model 20 live? I dumed a bundle of $ into it and it fits great I hope I won't have to go to a 9in. Any opinions will ease my mind. Thanx Scramboy.
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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/27/2017 at 9:15am
550+ hp should do fine. It's when you get passed 700+ it starts to have issues. I think the caps will give up before anything else.
71 Javelin SST body
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NASCAR SB2 rods & pistons
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tufcj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2017 at 9:53am
The biggest weaknesses in the Model 20 are the tube welds, spring pads and 2 piece axle shafts. I think you've addressed about all of the weaknesses. The only thing you didn't mention was replacing the crush sleeve with a solid spacer and shims. That stabilizes the pinion bearing preload. The ring gear is 8 7/8" diameter, only 1/8" smaller than a 9", bigger than a Dana 44 or Ford 8.8. It should hold 550 HP without a problem with the mods you've made.

Bob
tufcj
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cricket Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2017 at 8:19pm
Naah, way to weak, sell me yours for 50 bucks, and just go full tilt bogey with a 9 inch Fraud rear!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2017 at 8:53pm

If the crush spacer is gone,
I'd just keep an eye on it as the power and traction ramp up.

 With enough of traction,
 the thin axle tubes and 8 lonely ring gear bolts would probably be the first to complain



71 P-code 4spd Javelin/AMX
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ttrrogg Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2017 at 4:56am
A dana 20 is an 8 7/8 inch rear about the same as a 9 inch ford. If you change the the axles you should have no problems. Been there done that for 500hp.
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SC397 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2017 at 10:54am
The Dana 20 is a Transfer Case.
The AMC Model 20 Axle has been around since the '50's. A very strong unit with the modifications that you have made. I say drive it like you stole it!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2017 at 4:40pm
In the case of wheeling, would it make more sense to rely on a deep geared Model 20 or Dana 44? Would the axle still be the mechanical fuse in that setup @2.72 or 3.08 gearing? I've always had questions about the Model 20 axle and can never find it. I think it's my actual go to preference because it would be a drop-in swap but I'm also curious about the 44. Ermm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2017 at 5:47pm
I run a 9" in mine but I am also well up there in power these days. I wouldn't bat an eye to put 700 hp through a model 20 with a few options to beef it up. Weld the tubes, change to solid axles and maybe even add a truss if you are worried that much but that is not as vital or as beneficial in a drag application. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2017 at 6:28pm
Originally posted by DaemonForce DaemonForce wrote:

In the case of wheeling, would it make more sense to rely on a deep geared Model 20 or Dana 44? Would the axle still be the mechanical fuse in that setup @2.72 or 3.08 gearing? I've always had questions about the Model 20 axle and can never find it. I think it's my actual go to preference because it would be a drop-in swap but I'm also curious about the 44.


What size tires are you running? 2.72 or 3.08 on the trail would be terrible with anything but 26" street tires. I spun a couple of 2 piece AMC 20 axles with 35" tires on my CJ. I went to a Dana 44 rear before 1 piece axles were available for the 20. The 44 held up fine, the axle shafts in the Dana 30 front became the weak link. When I went to 37" tires, I upgraded to Dana 60 rear and 44 front, never broke another axle. The U-joints in the driveshafts became the weak link. I ran 3.73s in the AMC20, ran 4.27s in the 44. I went to 4.88s with the 37s.

Bob
tufcj
69 AMX
74 Javelin AMX
67 Rogue

If you need a tool and don't buy it...
you'll eventually pay for it...
and not have it.
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