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Discussion Starter #1
I confess to being a jeep newbi but have been drag racing 20 years and am changing hobbies. Would appericiate any and all opinions.
I already have an all aluminum 400 sbc going together for low speed torque and front and rear 60s that I am going to incorporate into "project jeep". I want to run tires in the 37-40 range and will be mostly running creeks trails and some hills, not to interested in rock climbing for now. I am ready to order a trans. and an atlas case and will be shortening the rears while waiting on them to arrive. I will be building a tube chassis under a "j" cut tub. I have 3 or 4 questions but realize the answers will be best provided in suggested combonations. I hope I have included enough info on where I am wanting to go with this, without being too long. Here are the questions.

Which Automatic Trans ??

Which ratio in the atlas ??

Which diff gears.??

Best width for the axles.??

Thanks in advance to anyone kind enough to share thier experience in the jeep game.

TonYJ
 

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Open for honest advice?

If so, skip the atlas, 60's, 37-40" tires, your not ready.

If your completely new to the hobby, wheel a stocker and learn to drive first, or continue building, but wheel a stocker while your building so you have the skills to use what your talking about. There's already too many out there with vehicles more capable than the drivers are.



And this should probably be in the newbie section. Ya caught me in a good mood.
 

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If you sit here and read on this board you'll come up with the answers you seek. I could give you my opinion, but it will be just that.
Transmission? Run a TH-350, or TH-400 for a trailer queen, and go with a Vette servo'ed 700-R4 if your driving it to the trail and if you got the wheelbase (Over 94"). Hell, if it's strickly a trailer rig. Go with the lowest gears you can, and read the latest on the Powerglide. You already know how strong they are!
Oh yeah, Some like manual boxes like the SM-465? Go figure...
 

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Discussion Starter #4
I spent some time off road in 2003 doing the hummer challange at and had a blast but decided the H1's were too rich for me to be offroading with so I decided to build a Jeep. For what it is worth we did win the sportsman Div. and third all around. So I've been off road a good bit. I am running a near stock YJ now " tires only" while building next springs new ride. My main thing is that I have built tons of cars and trucks in the past and want to try and do a better job of trying to choose the right combination of parts. It costs a lot less that way. A good plan up front is just less expensive in the long run.

I am going to be ordering parts this week so I can start fabing the frame and would appericiate feedback.

I do not want a pure trailer queen but am just not concerned about mileage for the short road trips I will make. I will want to be able to run down the road 65 when desired so max low gears are not part of the plan.
 

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OK, now I see that your running a YJ chassis. For a street driven rig I'd go with the 700-R4, but the atlas case? Can't you run a GM case that will put the driveshaft on the correct side you choose without the added cost of such an expensive box. I run 3:73 gears with 33" tires and a TH-350. I run about 2200 RPM at 55 MPH.
If you choose a manual trans go with the atlas box for gear reduction and twin stick shifter. With an Auto you've got many more options with the torque multiplication created. Use your tire size to figure your diff gears that I know your used too. One thing, don't run a locker for a street driven rig in the rear. I run one in the front with a twin stick transfercase to shift in and out as needed. The locker in the rear and short wheelbase equals Danger!
 

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Discussion Starter #6
We got rid of our hummer and recently sold the race car so I have some $ to put back into toys. Spent a good bit on shop equipment I always wanted but now on to the jeep parts. I just like the attributes of the atlas, short, strong, light, versatile. Gotta have it. Want to run big tires and build to sit as low as possible. Atlas is easy to clock flat. Hell I just want it I guess. Most of my questions come down to crawl ratio with an automatic transmission. I've done the searches but still don't have the answers.
 

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My crawl ratio is 64:1 with auto atlas 4,3 5,38s and 39,5". If I were you I would go for the atlas 5,0 and run 4,88 in the diffs so it would keep the crawl ratio and be more hwy friendly.
 

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If you run the 700R4 you will have the overdrive for the road but it will suffer under the power of a built 400sb if it's not built up. You will also need an adapter at the end of the 700 to mate with the atlas (go figure :rolleyes: ). The other thing that $ucks is the cost of the computer for the 700.

Whatr side are you running your diff on?

If money is no object then I say do for the 480LE
 

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trans

It takes no computer to run the 700r4! it takes a computer to run the 4l60e or the 4l80e.
 

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If I had it to do over, I'd run a TH400 and a shallower gear set. You'd get the power from the auto and have a lot more durability. I went with the 700r4 and a D300 for reference.
 

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cincinnatijeeper said:
It takes no computer to run the 700r4! it takes a computer to run the 4l60e or the 4l80e.
you do however need a B&M lockup controller which runs 150 bucks.
 

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Discussion Starter #17 (Edited)
Thanks guys, I made a decision to go with the 700R and 3.8 atlas with 5.13 gears. My local tranny guy done me up a 700R a couple of years ago for a big block car application and it has done well so I think the durability is covered. The lock up is handled by a simple switch on the dash. My tranny is ready to pick up tomorrow but I have not ordered the atlas yet. I am still a little unsure of the 3.8// 4.3 thing yet. I guess I am thinking the wheel speed of the 3.8 could occationally be a good thing "mud", but still be adequetly low for rockin. The $200 bucks cheaper for the 3.8 is also good.

Also someone asked about wheelbase and I am building a new rig from the ground up with a JP cj8 bobtail tub.

Doug...
 

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mud runners don't have anything to do with a 4:1 case. You want a d300. at 2.6:1. 3.8:1 is already overkill.
 
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