gear reduction options for amc th400 or t18 d20?

[wheelinjp]

I am thinking of building the 78 cherokee into a serious wheeler that I can beat since the runner is so clean it is a shame to hammer it. I have a 6to1 t18 with a dana 20 in a j20 or the rig now has a th400 with a quadrapuke. I dont know much about this running gear. I might still run a sbc with either a sm 465 and 203 to 205 doubler or I can go auto like Ive always had. I want to run one tons and 40-42in tires so a cana 20 isnt going to cut it. Let me know some options if any. What are the amc guys running?

 

[TreeClimber]

My old jeep was a AMC360 to a T18 to a D300 (from a Scout).

My current jeep is an AMC401 to a TH400 to a Atlas.

You'll need to keep into consideration, the Dana20 has a centered output for the rear diff, yet the Quadratrac has an offset output for the rear diff. Yes, you can run a D20 with an angled driveline to the offset axle that's already in the Cherokee, but it's a lot less streatable if you do so. So that's a good time to do a rear axle swap also.

 

[wheelinjp]

My old jeep was a AMC360 to a T18 to a D300 (from a Scout).

My current jeep is an AMC401 to a TH400 to a Atlas.

You'll need to keep into consideration, the Dana20 has a centered output for the rear diff, yet the Quadratrac has an offset output for the rear diff. Yes, you can run a D20 with an angled driveline to the offset axle that's already in the Cherokee, but it's a lot less streatable if you do so. So that's a good time to do a rear axle swap also.

THanks I have a 14bolt and will be looking for a pass drop front dana 60 so axle clearance is covered. I wont run a dana 20 since they are fairly weak and I want to do something in the realm of 4 to 1. I will likely run a 5.13 or 5.38 what ever is lowest for a 14bolt. I am mainly trying to determine if I should just plan a small block chev swap since it is so cheap and easy. I will probably go with an auto also since th400s are cheap with an np 208 on them. THen I can go 4 to1 dana 300 or atlas. Just wanted to see if there was any new idea or thing out for amc trannies.

 

[TreeClimber]

2 cents worth.

IFFF, you are really considering a Chev motor swap, then it's probably in your best interest to just drop the whole Cherokee idea completely.

AMC TH400s and Chevy TH400s don't have the same bellhousing bolt pattern, and also have slightly different outputs to the transfer case. So, if you go Chevy powered, you'll be replacing the motor, transmission, transfer case, rear axle, and both drivelines. Plus, some of the early Cherokees have a two piece front axle thingie (doubt yours does, but some did). Anyhow, you'll end up with a complete! rebuild of the entire drivetrain and you'll be installing it into an ugly, big, treebashing brute.

So, if'n I was you, I'd keep looking.

That said, you can install Bronco D20 gears (2.46) into the AMC D20 case (2.02) and that case can easily handle V8 power. There are also HD rear outputs available now, and twin sticks. Novak also makes a HD adapter to replace the cast aluminum factory one for the TH400

Or, you can install a Scout D300 (direct bolt in) behind the T18 if you want. It's a 2.62 low range.

The Novak Adapter website is a great read on the interchangability of parts, and in general a great source of info for what works, and who made what.

T

 

[TreeClimber]

Do yourself another favor, look that motor over really close. It looks like that's a Cherokee "Chief" package, and some had the AMC 401 motor in 'em. The 401 is externally ballanced and has some wierd things about 'em. Little more power, and some better internals, but harder to work with in some other areas. Anyhow, if you don't build it, I've got a buddie who's looking for a core.

 

[Corey Y]

shagg'n wagg'n

How much will your buddie pay for a 401? I have two complete motors i'd sell for the right price.

 

[TreeClimber]

How much will your buddie pay for a 401? I have two complete motors i'd sell for the right price.

He's looooww budget. Either one of yours dissassembled, in parts, or otherwise nearly worthless? Just need a few parts and pieces, but a rebuildable core would be nice for nearly nothing. Send me the info via a PM, as I'd like to keep this on topic. Thanks.

 

[wheelinjp]

2 cents worth.

you'll be installing it into an ugly, big, treebashing brute.

T

This is the idea. ANything i build is going to have to be beaten and I already started on this rig. THis isnt my first rodeo. I have always stayed with chevy drivetrain and was curious if there was anything new people figured out with the seemingly worthless amc stuff. It has a 360 2bbl in it now with a th400 and a quadratrac. I have no issues with doing a drivetrain swap to a fuel injected small block and a gm th400 with a dana 300. That was the last swap I did with my one ton YJ I built a few years ago. I am not on the fence about my choice of vehicles, just wondering if there was any new stuff out there for what it came with. Every time I build a rig it has a straight nice body and I hate the thought of denting it up so I dont wheel like I want to with it. Well now I am in the same boat again with a 4runner I am just wrapping up. It is worth much more done and dent free than to destroy it like I already started to with this cherokee. So I will likely do what I talked to leadfoot about and go 355 with flat tops, vortec heads, rv cam, and bigger fuel injection like the 4bbl projection, sm465 to a 203, to a 205 giving me 4 to 1 and run full width d60 front and 14bolt rear on cherokee chief 7s up front and stock rears with a shackle flip. That should clear 40s with alot of trimming. Thanks for the help.