which power train to choose from for 68 CJ 5

i currently have two possible power train choices for my 68. now the reason i am deciding between the two, is because a frame swap is mandatory. i'll be using .120 2x4 boxed tubing. i'll be somewhere between 86-90" wheelbase. my old frame had too many bad plating jobs, and too many different welders/processes over its life. not to mention the massive crack i just put in it on a "shakedown" wheeling run.

the first; stock 225v6 rochester 2 barrel/hei, sm 420, d18, warn overdrive. motor is only 3yrs old from full rebuild.

the second; 1988 TBI 350, th350, d18, warn overdrive.

i have d44's front/rear truetrac in rear, track-lok in front 5:38's, and hydroboost.

i have the chevy truck already. everything is falling apart, except for the motor. it's strong i drive truck everyday and, it is a 4x4 5spd. i also have another d18 t-case with the th350 novak adapter. (i picked it up with adapter for 200.00) all i need is to get a th350 transmission.

just wanted to get some opinions on what others may have used, and how it worked out for wheeling/driving.

whichever combo i use in the cj5, the spare setup will go in a willys or another cj5 platform. too many spare parts, and i'm a jeep addict.

 

225v6 rochester 2 barrel/hei, sm 420, d18, warn overdrive. great combo

 

With 5.38s you never have a need for the horsepower of the 350. Don't really need to go zero to 30 in 2 seconds.

 

I think the main choice is whether you want the automatic or the truck 4-speed. It's a different driving style for each, and you will have to decide. Having super low gears does not help as much with an automatic - indeed, it may be a disadvantage. The TH350 can be adapted to the 225 pretty easily, and then you'd have the advantage of the short/front distro V6 which fits the CJ-5 engine compartment better than the 350. But it's not a big issue - plenty of Chevy V8s have been put into CJs. I would want front or front/rear disks with the automatic too.

You'll need to remove the tail shaft of the TH350 to fit the Dana 18 to it, so you're going to have it completely apart. I would take the opportunity to rebuild the transmission at this point, and include my choice of performance features.

 

All about how your going to use that vehicle.........off or on road? The 225 is not the best choice to run on the freeway even with the OD...........the 5.7 as you already know is no issue.
Off Road the 225 is well suited with the right gears as is the 5.7 with the auto and the right gears.......with the longer chassis the auto will be fine with no short rear drive line......................either one will fit in the space up front. The 5.7 is fuel injected which might be a deciding factor for many. A good Brake package as Tim mentioned should be had on either choice.
Nothing but Choices.

 

thanks for the replies. the 5.7 is very low on hp. so I'm not going to do anything to it beyond rings, main bearings, and some valve seals. (poor man's rebuild).

my main concern is that the wheeling (rubicon/fordyce) is up from me in elevation. the drive up with the v6 is less than favorable. i prefer to drive in; drive out. i enjoy the total jeep experience on and off road. i have front disk brakes from the wagoneer.

what about the 700 r4? how much more length than th350?

 

700R4 / 4L60 vs the th350?..........the 700R4 is about 1.5" longer overall to use the 4-speed w/OD.......check w/ Novak Adapters for exact measurements. I would also guess the adapter for the Transfer Case is the same thickness for either.
The 700R4 is a great option with the lowest low gear of all the GM Auto Trannys at 3.06:1 and with the 30% Overdrive in 4th opens up some interesting options whereby you can have some great low gears in the axle's but once in 4th gear it all now becomes Freeway gears.

I liked it so much I'm using one in my current build!

 

This is interesting to me. Is it because the auto needs more "whoa" when holding back in Drive (to overcome the torque converter) than a manual requires? No question disks are better, just curious about the relationship to an automatic transmission (and because I'm debating a disk/disk or disk/drum setup on my '75 CJ5 w/ T-18 which currently has drum/drum).

 

Well, yeah. The disks don't fade as much as drums do. And you don't have compression braking helping you with an automatic. Typically you drive an automatic over broken ground with a two footed style - one foot on the brake and one on the throttle. Your progress forward is mostly controlled by how much you release the brake. You just need to give it more than enough throttle. This both requires that the brakes be up to the task, and makes a lot of heat in the transmission. So you also need extra good cooling with an automatic, both to dissipate the heat the automatic makes, and to handle the extra heat that the transmission will be putting into the engine cooling system.

 

i've never actually wheeled an auto trans in a jeep before. it's something i've been curious to do. now that i've amassed enough parts to basically do the conversion, it seems the right way to go. from the novak site it looks as if i would need a different adapter for the 700r4 trans. it's easier with the th350 given what i've got already.

i've converted the front grill to a later cj style, with a larger v8 radiator. i plan to use a later hood as well. i'm running aftermarket/homegrown flat fenders, so they'll be extend to fit.

 

i'd like to put that combo i have in a hi-hood willys like yours.