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March 2006 4x4 Tech Questions - Techline

Willie Worthy | Writer
Posted March 1, 2006

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Question: I own an '85 CJ-7 with a 258 six-cylinder and four-speed. I want to swap in a '67 318ci V-8 which came out of a Dodge Charger. I'm going to back it with a TorqueFlite 727 automatic transmission and an NP208 transfer case. Will this be a hard job to do, and what will I need to accomplish this swap?
Arnie Odom
Interlachen, FL

Answer: A I am surprised we don't see more Chrysler small-block V-8s used as engine swaps. The first V-8 engine swap I ever saw was a 318 Chrysler in a CJ-2A-in 1960.

The Chrysler small-black is about the same weight as a Chevy V-8, maybe even a bit lighter, and with stock exhaust manifolds they are 1 inch narrower. Their biggest problem is that they are about 3 inches longer from water pump to bellhousing. However, in your case, that's not a problem, as that's still 2 inches shorter than the AMC six you're replacing.

Advance Adapters (www.advanceadapters.com) has the motor mounts you will be needing under PN 713095. Novak Conversions (www.novak conversions.com) offers them under PN MM 32. You're going to also need a rear-sump oil pan as most of the pans use either a front or center sump (Chrysler PN 5249062). You will have to design your own crossmember/transfer-case mount, but that shouldn't be too hard.

You're definitely going to need a new radiator to handle the extra cooling requirements of the V-8. Advance Adapters has both copper/brass or aluminum radiators with built-in transmission coolers available. However, the radiator mounts were designed for the '87-'04 Wrangler. Whether those mounts could be adapted to your CJ-7, I'm not sure, but perhaps by parking your CJ next to a Wrangler you could do some comparison measurements. That's not to say you couldn't adapt a radiator from another vehicle with a bit of ingenuity.

One advantage of the Chrysler engine is that the starter is on the left side, so you don't have to worry about driveshaft clearance. Where you may have a problem is the overall offset of the 208 transfer case, as it's a bit wider than the Dana unit you're replacing. You may end up slightly offsetting from center the complete engine, transmission, transfer case package to gain enough clearance next to the right-side framerail. You may also have to modify the firewall and floor area to accommodate the larger Chrysler automatic transmission.

Keep in mind when mounting the engine that you want to keep it as level as possible. When you drop the back end down-say, for floor clearance or better rear driveline angle-you're also increasing front driveline angle. A lot of people don't take this into account and end up with a front shaft vibration emanating from unequal U-joint angles.

Question: I have been bitten by the drivetrain swap bug and have my parts choices: TH700R4/Klune V/NP208. The only fly in the mix is the slip yoke on the back of the GM NP208. It seems that Ford 208s have yoke rear outputs. Can a hybrid be constructed?
Ken Wetherall
Concord, CA

Answer: Sounds like a great idea to me, so I checked with Vince at 4xHeaven in Gloversville, New York (800/800-1679, www.4xheaven.com), whose specialty is rebuilding transfer cases, and he gave me the straight scoop.

Yes, some of the Ford 208s did indeed have a yoke instead of a slip yoke, but the output shaft and the rear of the case are different. OK, what about using the complete Ford 208 up to the Chevy transmission? Again, we strike out as there are just too many differences, including the clocking, as well as shaft spline count. He said that he has looked at all sorts of combinations trying to make work exactly what you're trying to do without any practical luck.

Question: I recently bought a '96 Dodge pickup extended cab that I use as a work truck and a hunting truck. I have some future plans for it, but right now I am hoping that you can help me with a problem. Whenever the truck is loaded heavy and I pull away from a stop, I get this shuddering that feels just like a clutch chatter. However, the truck runs an automatic transmission. With the bed of the truck empty, the problem goes away. Is there something wrong with the transmission? I have checked for loose motor and transmission mounts, and they all seem to be in good condition.
James Blain
Cody, WY

Answer: My guess is that it is a driveline problem, mainly because you say the problem only occurs when heavily loaded. I have heard of other Dodges in the '95-'96 range with this same problem. I think that the weight in the bed and the spring flex is causing the rearend to either turn upward or actually become lower than the carrier bearing, resulting in the differential yoke being in misalignment with the driveshaft. I am sure that you have noted that your truck uses a two-piece driveshaft with a center carrier bearing on a crossmember.

There are a couple of ways to solve this problem, and if the truck was mine, I would incorporate both of them. First, your truck is about 10 years old, and if it's been used as a work truck, then there is a good chance that the rear springs are pretty worn out. Maybe it's time to have the rear springs rebuilt and possibly add a few more leaves for good measure. Yes, the added spring leaves will affect the ride quality when unloaded, but it will also keep the rearend from sagging. Keep in mind, however, that just because the springs can handle more weight, you don't want to exceed the truck's rear axle weight rating, which should be posted on the door frame.

The second thing that I would do is eliminate the two-piece driveshaft in favor of a single-piece longer shaft. You will need to not only take out the carrier bearing but also the crossmember for proper driveshaft clearance. The longer shaft will make for much better driveline angles when either empty or with a load. Just be sure that the shop that does the work uses a large-diameter heavy-wall tube to prevent any driveshaft whip at highway speeds.

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