Looking for feedback for build plan

I'm thinking of getting out of the big rock monster and back into something a little smaller and better suited to trail riding. My reading on this site provided a lot of inspiration to go this direction, so I'd like to get you guys' opinions. I've got a 1975 CJ5 and figured I'd go with this setup:

1975 CJ5
Stock D30 and D44 axles
Big joint kit for front axles (equiv to D44)
2 1/2 inch lift and extended shackles
Ford 302 and T-18 out of my rock rig
Keep the Dana 20 and throw in a 3:1 kit
33" tires
4.11 gears which would give good cruise at 55mph.
ARB's front and rear
8k winch

From what I've experienced on the trails, this setup should handle 99% of the trails in Colorado and Utah, although it is a little short on wheelbase. It should also still be docile enough that my wife could drive it to work if she wanted.

What do y'all think?

 

Sounds good to me

Should make you a nice trail rig.

 

Stay away from the extended shackles. They could cause handling problems. If you still need the extra lift either do a 1" body lift or go with a larger lift spring.

Other then that is does sound good.

 

I should probaby clarify extended shackles. I'm only thinking one inch over stock (1/2 inch lift), more to improve suspension travel than gain lift.

 

I think your decision is a smart one and is close to the options I’m using on my CJ3B. I do like the article on this cite about using some 3-inch lift wrangler springs and going SUA for a smooth street/off-road ride and some articulation. But, your decision for a good street/trail rig sounds good.

 

That's real close to what I run. You'll be happy with that. If you are going down from a big purpose-built rig, you'll find that once again, trails are challenging and fun. I don't understand all these overbuilt rigs, especially in more moderate areas -- I don't want technology to remove all the challenge.

I have a '73, pretty much what you described, but with 258, and no lockers yet. Big things I want to do is lock it, go with heavier front shafts, and a full cage. I am 3.73 now, probably going to 4.56's when I lock it. I don't highway much, it's usually in-town or on dirt.

I agree with tumbleweed, not sure you'll want the 3:1. You'd be a little too low for trail riding. That'd be more better for rock "crawling", but worse overall for general trail usage.

 

I've been mulling that decision over pretty heavily for exactly the reason's you bring up. My Bronco had the NP208 with 2.7 gearing and low was always too low for the trail between obstacles. I could use a higher gear in the tranny, but that setup was noisy. The 2:1 is a great trail range and may win out over rock capability in the end. Another factor I don't understand yet is weight. With my 5500 pound rock machine, 120:1 gearing is required, a little deeper wouldn't hurt. With a 3000 pound Jeep, I'm sure all the rules change a little.

Thanks for all the good feedback. It's very encouraging

 

Sounds like a good, plan, but with my quirky preferences I would do a few things differently.

I think the swap from a 258 to the 302 is pointless, considering the small number of CI that you will gain. The 258 has a favorable torque curve and smoothness, and is already in the engine bay. Sell the 302 to someone building a street rod.

In my experience, a 4.27 ratio is fine, though the 4.10 ratio is more popular now for some reason. 4.27s with 33" tires is 2300 RPM - low for modern engines. Personally I would try to cruise between 2500 and 3000 RPM.

What kind of crawl ratio do you want? 6.32*3.0*4.10 = 78:1 With 33" tires, that's 8.63 ft/revolution, and at 1500 RPM you will be travelling at 2.45 mph or 3.6 ft/sec. You can improve that by turning the engine slower (more low RPM grunt = longer stroke -> 258), increasing the axle ratio to 4.27, and/or using shorter tires. If you have enough power at 1000 RPM, and have 4.27 axles and 31" tires, you'll be going 1.5 mph or 2.2 ft/sec with that same crawl ratio. The granny gear makes a big difference, but the smaller factors add up.

 

You mean, upshifting to 2nd? The T-18 gears are noisy, but they can't be noisier than the granny gear (!?)

The transfer case upgrade can be done later - I'd say build it without and see if you like it.

 

The 302 I have was built specifically for rock crawling in the 5500 pound rig. It has great torque in a small package, already has custom fuel injection and converted air (OBA), and only has about 5000 miles on it versus who knows how many on the 258. It also doesn't need an adapter to fit the T-18. I've finally gotten the CJ on the road a bit with the 258 and must admit it's an impressive little motor. The decision between swapping and keeping may boil down to how much it costs to swap in the tranny and installing fuel injection (my system supports TBI), versus swapping in the whole engine and tranny as a unit. Fab isn't an issue, and my work is rock solid, so the work involved in the engine swap doesn't figure into the swap/keep decision very heavily.

Crawl ratio versus highway gearing is always a problem. I like 100:1 plus (150:1 would be a dream) for technical rock work. But, the Jeep won't be built to handle that type of abuse. My Bronco did well at 77:1, I think the Jeep will do even better since it's about half to 2/3 the weight. It is easy to do the tcase conversion later, so the suggestion of holding off on it is good.

Changing from 4.11 to 4.27 has minimal effect on cruise and crawl ratio, so the small increase in torque would be worthwhile. I'll keep that in mind. 4.56's may even work as I don't really see being comfortable pushing this thing over 55mph (I like highway cruise between 2300 and 2500 for a V8 for mileage reasons), and the crawl would go to 82:1 with the TeraLow kit.

The way I design a vehicle is to use desired tire size as the driver for everything else except the engine, which I leave up to personal preference. That's why an auto or the stock three speed are not strong contenders (ignoring the converter multiplication), they just don't have the gear multiplication I'm after. I'd like to run 35" tires, but that requires more lift, driveshaft mods, dropping the tcase, etc. 33's provide the best compromise between ground clearance and an a large jump in build cost.

Thanks for your opinions timgr!

 

Sounds like you have it figured out pretty well! I'd definately go with a fuel injected engine and if possible an OD setup. The only flaw I see in your plan is using the short cj5 body. It will be a little lighter and more manueverable, but it will cost you in comfort. Sounds like it will have less space than your current rock rig. 100miles to and from trails plus time on the trail and you will be wishing you had a tow rig! Perhaps thats not a big issue for you though.

Otherwise, rest of the plan sounds good!

Kevo

 

for TBI FI on the 258, go with the 4.3 TBI

here is a good writeup on it: http://www.bustedjeep.com/projects/junkyardtbi.asp

 

I'm hoping the Notch will help with leg room, but the ride is a little rough

 

I just checked the compression on my 258. 120 lbs per hole +/- 1 lb. It doesn't smoke and runs great, guess I have to rethink that part...