40s on AMC20 and D30??? - Page 2 - JeepForum.com

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post #16 of 27 Old 11-15-2011, 09:06 PM
ytowntj
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Wheel that same setup right now on my 85, never had any trouble and go places that locked TJs with 35s go
Its certainly not a bad setup, it is definitely possible to break either one with enough stupid pedal though.

Heck I broke a TJ 30 shaft open on 32s and it has bigger ears and joints.

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post #17 of 27 Old 11-15-2011, 09:13 PM Thread Starter
broach70
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Originally Posted by ytowntj View Post
Its certainly not a bad setup, it is definitely possible to break either one with enough stupid pedal though.

Heck I broke a TJ 30 shaft open on 32s and it has bigger ears and joints.
My thing was moser shafts, weld the tubes, and truss it with 30 splines, that was my plan, probably running a vortec motor and same setup for the D30, its more of a cj thing to show up on the trail and wheel hard with those axles because everyone hates on them so much was why I really wanted to do it
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post #18 of 27 Old 11-15-2011, 10:40 PM
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Originally Posted by broach70 View Post
A guy had 360 punched out to 434ci launching it at 4500rpm and running nitrous to a AMC 20 rear for mud and sand drags (my guess was paddle tires) so no im not kidding that was my reason for asking.
There's no way to just "punch out" a 360 to 434ci. You'd have to have at least a 4" or larger stroke crank, with a healthy overbore. With a .060 overbore and a 4" crank, you're still at 430ci.
Stock bore/stroke for a 360 crank looks to be 4.08/3.44
I'm not up on my AMC stuff, but I don't see that being possible.

'76 CJ5
434 pump gas SBC with an NX/HVH plate system
th350/Coan 5,000 converter/Dana 300 tcase
Dana 30 front with 4.56's/Dana 44 rear with 4.88's
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post #19 of 27 Old 11-16-2011, 12:46 AM
80cj
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Originally Posted by mopar346 View Post
I think Jeephammer lauches and totes on a 20 so I would like to here his thoughts, I believe the ring gear is like 9.75. The axles, case and tubes I hear are the weak links in a 20. The 30 however is like a GM 10 bolt used in the S-10s.
AMC 20 ring gear is 8.875. The 30 ring gear is 7.2" whereas the S-10 rearend is either 7.5 or 7.625 depending on the year.
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post #20 of 27 Old 11-16-2011, 04:49 AM
Foundrydude
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The 40s are the killer variable in this question

You can only stress an axle as hard as the tires will hook. Increase the traction and you're increasing axle stress.

Can you run them? Absolutely. Are you willing to live with the consequence of being deep into places that require 40 inch tires to get to then having one break? That's a question for you, not for us.

Sand and mud drags are a lot different stress wise than something that drives to the trailhead. Some of your greatest stress with 40s and welded spider gears is gonna happen in a convenience store parking lot when turning tightly and forcing those big 40s to slip on concrete cause the differential can't differentiate.

IMO there's a lot of places it's fun to dare to be different but axles aren't really one of those places.

good luck with the truck!
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post #21 of 27 Old 11-16-2011, 06:23 AM Thread Starter
broach70
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Ok so if I went to a 37" tire, I know its still up there but is it still as crazy as 40"s with those axles tubes welded and trussed?? More than likely it will be spring over to start off with anyway until I can get the money to link it up.

And very good points foundry dude, never thought about it that way. It will be strictly a wheeler though
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post #22 of 27 Old 11-16-2011, 08:13 AM
ytowntj
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Your still not getting it. Low hp, You could run 35s pretty reliably with the setup you mentioned and some better front shafts. Add some horsepower in the rocks and its not going to be pretty.

People run tons for 37+s for a reason.
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post #23 of 27 Old 11-16-2011, 08:25 AM
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You can weld and truss all you want, but the bottom line is the axles, ring & pinion and u-joints just aren't strong enough to hold up to the horsepower and the size of the tires. By the time you put all the money and time into those axles you could have easliy built some D60's & 14 bolt that would truly hold up to what you want.

It's a Jeep Thing, Chrysler Doesn't Understand!
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post #24 of 27 Old 11-16-2011, 08:32 AM
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Why the HP? It's all about gearing and your torque in the rocks..... I run a '94 4.0L engine and am completely satisfied with it. Also, for rocks I'd say 33's would be my limit on that Dana 30....... Maybe I'd try 35's on the AMC 20 if it was trussed up and a good set of one piece axle shafts.

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post #25 of 27 Old 11-16-2011, 09:32 AM
CSP
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If you're going to go big, do it right and don't be a cheapskate. It will cost more in the end.
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post #26 of 27 Old 11-16-2011, 10:51 AM
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Good luck trying to stop them with stock Jeep brakes.
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post #27 of 27 Old 11-16-2011, 04:05 PM
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Originally Posted by CSP View Post
If you're going to go big, do it right and don't be a cheapskate. It will cost more in the end.
This.
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