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March 2006 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on March 1, 2006
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Four Wheeler
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Los Angeles, CA 90048-5515.

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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 ( has the motor mounts you will be needing under PN 713095. Novak Conversions (www.novak 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,, 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.

Question: I'm confused, Willie. You, and Four Wheeler in general, acclaim the value of modifications to diesel engines to make more power, but if it's so simple to do, why don't the manufacturers-Ford, General Motors, and Dodge-offer this much power to begin with? And if I do the modifications such as a "chip," exhaust and intake, how is this going to affect the life of the engine?
Jim Smith
Los Angeles, CA

Answer: That's a really great question and one a lot of people should ask. A diesel mechanic friend, who I have great respect for his knowledge, once told me that "There are only so many horsepower-hours in an engine." Generally speaking, that is true, but more so with gas engines than diesels.

Let's look at diesel truck motors. To start with, all the components are quite stout. Additional weight isn't as big a factor in a truck as it is in a passenger car, so the blocks, heads, and reciprocating parts can be built heavier. With proper care, a pickup truck diesel will go at least 250,000 miles, while some big-rig diesels go close to a million miles between overhauls.

When Dodge first offered the Cummins B-motor in its trucks, it was rated at, I believe, 160 hp. Now this same basic motor is putting out 325 hp. Each year Ford, GM, and Dodge seem to raise the horsepower and torque levels of their engines.

How did the factory double the horsepower in the case of the Dodge? Basically, more fuel and more turbo boost. OK, maybe it's not all that simple as there are other factors involved. But we are still talking about the same basic motor.

It's not uncommon for people to modify their diesels to produce well over 500 hp and 1,000 lb-ft of torque and still maintain good driveability, fuel mileage, and a long life expectancy. Jim Bigley, founder of The Diesel Page (, has a Duramax in an earlier Chevy pickup that runs 112 mph in the quarter-mile and gets 25 mpg at freeway speeds! The secret? Well, it's not really a secret. It's that maybe only 10 percent of the time, and probably a lot less than that, the motor is ever making that much power. The rest of the time, it's just happily cruising along at a low rpm. Just how often do you drive at full throttle? Not much, unless you pull really heavy loads in mountainous terrain. Then it's a simple matter of backing off the throttle a bit to keep boost pressure and exhaust gas temperature in check.

For example, my own tow rig is an '01 Duramax that through modifications makes well, a lot of horsepower and torque. Yes, there are times I back off the throttle. I don't make hard pulls in 6th gear (overdrive); the engine can handle it, but I'm not sure the transmission or clutch can. I use synthetic oil and make changes at the 5,000-mile mark, even though the manual says I can go 7,500. I expect this motor to last an honest 250,000 miles.

Then why don't the manufacturers offer these extremely high horsepower and torque levels if it's possible to keep the engine alive? Because to drive with (or should I say, make use of) this much power, you need a bit of common sense. You have to monitor boost pressure, exhaust gas temperature, and water temperature. You just can't put the transmission in gear and put the pedal to the metal, eat a burger, and talk on the cell phone. A modified engine under a heavy power load will easily exceed safe levels with disastrous results.

There is also the problem of controlling particulate discharge, or what is commonly referred to as "soot." Yep, that black stuff that comes out of the exhaust pipe and gives diesels a bad name. As power goes up, more black stuff comes out. Then there is the problem of excessive exhaust gas temperature, which can melt aluminum pretty darn quick-and being that the turbo is made of aluminum and runs off exhaust gas, it's pretty important to keep a close eye on things. The truck manufacturers don't like paying out warranty claims any more than owners like to have their engines fail, so there has to be a happy compromise. However, it seems that each year, they find better and safer ways to make more power.

Question: I recently purchased a Dodge Ram 1500. I love it! It has tons of power with a manual transmission. I want to start modifications for performance but gas is an issue. What are the best modifications to make that will give the best fuel economy while still increasing horsepower?
Kathy Bennet
via fourwheeler.comv

Answer: Actually, a couple of the things that gain performance will also enhance fuel mileage. These are such bolt-on items as headers and a good after-cat exhaust system, as well as an open-element, high-flow air filter. Payback, however, will take a long time from the minimal mileage increase that is offered.

Also consider using a synthetic lubricant in the gearboxes, as they can show an increase in fuel mileage. For all the changes you make, don't expect more than a 10 to 20 percent overall increase. That is just about the maximum you can pull out.

Driving habits can also play an important part in fuel mileage, and I am sure that I don't have to tell you that slow acceleration and keeping your speed down will improve fuel mileage. Tires play an important roll in mileage too, with radial tires having less rolling resistance than bias-ply tires. Larger-than-stock tires can hinder fuel mileage due to higher rolling resistance and weight that has to be accelerated, as well as by air turbulence. And speaking of that, lift kits are a real killer of mileage, as they expose more of the underside to airflow turbulence that resists movement, resulting in more power and fuel needed to move the truck.

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