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August 2005 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on August 1, 2005 Comment (0)
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Question: Could you please tell me what the most durable and best performing aftermarket limited-slip differential for a Jeep TJ with a Dana 35 is?
Sgt. Cortland D. Marix
U.S. Army Transportation Corps

Answer: I wouldn't really recommend spending the money on putting a limited-slip in your Dana 35. It is not a very strong axle to begin with, and the limited-slips don't really offer that much of a traction gain. Superior Axle & Gear makes a special set of axles for the 35 that can be combined with the Ox Locker, Detroit, or an ARB Air Locker. The price is kind of high for the total package, but a lot less expensive than going to a Dana 44 rear axle and then adding a locker-which in my opinion is really the way to go.

Question: I have an '88 Jeep Grand Wagoneer with an AMC 360/727 combo that I would like to replace with an overdrive automatic transmission. The motor needs to be rebuilt, and I would like to do this at the same time. I was wondering if you could lead me in the right direction on what options are available to me. Is there a conversion kit available, or would a Ford small-block/AOD trans swap be better? What would be a good transfer case to use with one of these two options? Is it possible to use the factory case if it's adequate for this vehicle's purpose? I really like this vehicle but would like a little more mileage out of my daily driver.
Randy Jones
via e-mail

Answer: I believe that Advance Adapters and Novak Conversions have an adapter plate that will allow you to hook the AMC engine to a GM-pattern transmission. The easiest conversion would be the 700R4. You're also going to need an adapter to the transfer case, which either company will also have.

It wouldn't take much work to use a steering column out of a GM pickup, Blazer, or Suburban, so you would have the right shift linkage, or you could go with an aftermarket floor shifter. You will need a special plate between the carburetor and manifold that holds the throttle cable as well as the TV cable that controls the transmission's shift points. TCI has these available through Summit Racing. My guess is that you will have to move the transmission-mount crossmember rearward somewhat, as the 700R4 is a bit longer than the Chrysler-built 727, which also means some driveshaft modifications. Overall, it's a pretty easy swap.

Question: I am 19, and my dad and I have always enjoyed going out on four-wheelin' trips. Since I can remember, there has always been a Jeep in the family. We had an M38A1, two CJ-5s, and now a decked-out Wrangler TJ.

I decided to get into the frenzy and was able to get my hands on an '85 Jeep Cherokee. I was planning on putting in a still-good 4.2L from a friend's CJ-7. What I didn't know was that the 4.2L wouldn't fit in the engine compartment of my Jeep without a lot of fabricating. I was told it had a 2.8L V-6 in it at one time and was wondering if you guys had any ideas as to where I could get one of these engines so that I can get it out on the trails. For what I got this Jeep for, I can spend some money on a "replacement" engine.
Andrew Headley
Chandler, AZ

Answer: Cherokees can make super trail vehicles. As you have found, they are also reasonable in price. Swapping in either the 4.2 or the later 4.0 isn't impossible, but it's not the most practical swap for your early Cherokee. When Jeep went to the 4.0 inline-six, they made quite a few body changes, and while they are not that noticeable, they are substantial enough to make a big difference.

I would totally forget about finding a 2.8 motor. Even though they were used in the early Chevy compact pickups, they never were a very good motor and developed crank-sealing problems, as well as not really making a lot of power. Chevy made some 3.4L versions of this engine that solved these problems, and they can be bought as a "crate engine" through any GM dealer-they actually are a good replacement.

However, the transmission in your Jeep really isn't the strongest, and I would not recommend using it. What makes a great engine swap is one of the 4.3 Chevy V-6s. I would really suggest that you buy the complete package. That would include the engine, computer, wiring harness, transmission, and transfer case. While you're at it, get the driveshafts too. I have seen this done on several Cherokees, and the best word to describe it is "sweet." Yes, it is going to cost you a lot more money than I'm sure you expected to pay, but the results will be well worth it.

The later-model vehicles use a pulse generator to establish a signal to the electric speedometer. I believe someone makes a special adapter to change it over to a cable-driven speedo like your Cherokee has; however, the name of the company eludes me at this time. According to Robert Schleppy of 4x4 Used Parts (970/224-1133, www.4x4usedparts.com), you can just as easily swap the output shaft and rear housing from your present NP231 transfer case for the one on the Chevy-version 231 case. In fact, he made a Chevy-to-Cherokee swap like this several years ago.

Question: I am currently rebuilding a '59 Chevrolet Apache that is equipped with a 327 V-8 and a four-speed manual tranny. I am wondering what would be a good axle and transfer case for this engine and tranny.
Andrew Koecher
via e-mail

Answer: I am assuming that this is a two-wheel-drive truck to start with? I would suggest that you buy a complete pre-IFS truck. Park it next to your present Apache and start doing some comparisons, such as to where the new springs will have to mount, transfer-case crossmember and such. It will be so much easier to have a complete vehicle to work from, and it will keep you from making countless trips to the salvage yard for all the little things that you will need to make the conversion.

You can keep the present engine or swap it out for the one in the donor truck, as all the first-generation small-blocks have the same motor mounts as well as the same block/bellhousing patterns.

You could keep the present rear springs and axle if you like, as long as the gear ratio matches the front axle, or swap it out. If you do change the rearend, you will most likely find that you will have to relocate the axle's spring pads to match the old frame's width and perhaps make some changes in emergency-brake cable length. If at all possible, I would suggest that you try to locate a 3/4-ton truck, as the front and rear axles are of a stronger design. Look for a 1-ton truck if you can handle the additional cost. Then again, you don't say what your usage plans are, so maybe the 1/2-ton running gear will be just fine.

Question: I'm gearing up for an engine and tranny swap. I wish to put an '88 (or so) vintage 4.0L motor and accompanying AW-4 automatic into an '84 CJ-8 "Alaskan Postal." What has me concerned-yes, I'm keeping the Dana 300 transfer case-is that the motor in the donor Cherokee appears to be positioned farther forward, in relation to where the front axle goes under, than the 4.2 L/258 is in the CJ-8. I don't mind the idea of having to use something like a CJ-5 rear driveshaft, but this is beginning to sound kinda borderline as to the desirability of the swap. I want to install 35-inch tires and a spring-over with this swap. That's the picture I'm looking at, and-putting in a manual transmission to keep an overdrive doesn't really appeal to me, especially with right-hand drive.

In short, is the difference in length between the 4.0L/AW-4 motor and trans (front of motor to rear of 4x4-version trans) and that of the 4.2L/Chrysler three-speed auto going to cause problems?
David Heck
via e-mail

Answer: Lengthwise, the motors are basically the same. If anything, the 4.0 is a bit shorter overall due to water pump and pulley changes. It is closer to the front axle on the Cherokee due to body design. You should have plenty of rear driveshaft length with the longer wheelbase of the CJ-8.

Question: I have an '80 CJ-5 with a strong 258, T-176, Dana 300, 4-inch suspension lift, 1-inch shackle lift, and 36-inch Swampers. I want to install a set of Dana 44 axles from a Scout that I already have. I am not sure what year they are, but they have already been under a Jeep. They have not been cut down. I want to build the diffs with 4.88:1 gears, spool the rear, and install a locker in the front. This Jeep is for serious four-wheeling and sees little highway driving.

As I have been researching the front swap, I learned that front caster is not correct on the Scout 44. I know this can cause adverse driving conditions on road, but will it hurt my off-pavement performance or cause possible damage to the suspension components? This Jeep sees rock climbing, mud bogs, and hillclimbs (all the good stuff). I am capable of changing the knuckles to the proper caster, but don't want to put the extra time and effort into it if it is not going to hurt me on the trail.

Also, would you suggest a Detroit Locker for the front, or is there another locker that would work for me that's a little more "rear pocket" friendly? I don't want a limited-slip.
Solon Chenault
via e-mail

Answer: The Scout axle is not without its problems when making it fit under a CJ. You're right in that the caster angle is wrong-well, for some reason or another, it worked on the Scout, but your Jeep will require about 4 to 6 degrees of caster. The Scout specification is zero degrees for every year but 1980, when it changed to 1 degree.

As a bit of review, "caster" is what keeps the wheels going down the road straight and moves them back straight after a turn. Improper caster can also cause the wheels to wobble uncontrollably at certain speeds after hitting a bump. Ever pushed a shopping cart with the stem bent on the front wheel, where it wobbles like crazy?

Another problem is that with your 5 inches of lift, you have a very steep front driveline angle. To correct it and prevent U-joint/yoke bind, you most likely will try to turn the pinion upward. This will in turn cause the steering knuckles to go into a negative caster. This may cause all sorts of steering problems, such as the aforementioned wobble at low speeds, as well as the tie-rod hitting against the springs.

You could possibly solve this tie-rod clearance problem by drilling out the tapered holes in the steering knuckles and making a tapered bushing so that the tie-rod could now be installed from the top down. However, under full suspension compression, the tie-rod and the framerails may come in contact. I would suggest that you take the time to cut the knuckle's welds free and rotate them on the axletubes. No, it's not a fun job and takes a lot of time and effort to do. I believe that on the last one that I did with a Scout axle, I rotated the steering knuckles about 19 degrees to obtain the proper pinion angle and 6 degrees of caster angle.

Oh, yeah, one more thing-usually you have to build new spring mounts and move them out a bit wider than the frame in order for the right-side spring to clear the differential housing.

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