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September 2007 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on September 1, 2007
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Four Wheeler
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Los Angeles, CA 90048-5515.

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Question: I'm thinking of swapping the NP203 transfer case in my '75 K-10 Chevy for an NP205.

My truck has a 6-inch suspension lift, 35x14-15 Gumbo Mudders, a 350ci engine, and a TH350 transmission.

I know I need an adapter plate, but will my driveshafts have to be modified? What kind of shift linkage do I need? Where would you find an adapter plate?
Josh Henning

Answer: Yes, you will need a new adapter, and you're in luck in that the 350 transmission and 203 transfer case share the same coupler sleeve spline as the 350/205 combination. You will also need some new shift linkage. Off Road Design ( has new aluminum adapters, or they may be able to hook you up with a used factory cast-iron adapter. They also have some pretty trick shift linkage.

As to the question of needing new driveshafts, Steven Watson of ORD tells me that the front shaft will have to be 3 inches shorter and the rear 6 inches longer.

You might also want to consider keeping your 203 and combining it with a 205. This "doubler" will give you both a 2:1 and a 4:1 low range. With this combination of two transfer cases, the rear driveshaft will be the correct length and the front shaft will need to be 3 inches longer.

Question:I just opened up my own 4x4 shop, mainly dealing with the sales, and some installations. However, I've never set up a rear end and would like to learn the proper method and a source for the necessary tools. Yes, I have some service manuals but some leave a lot to be desired, such as saying to use factory tool numbers such-and-such.

I know that there have been lots of magazine articles about how to set up rear ends, but is there a book available that takes one through it step-by-step, and could you direct me to a source for the proper tools?
Name And Address With Held By Request

Answer: Up until a month or so ago, I would have told you to stick with service manuals, but Jim Allen has just come out with a 378-page book on how to rebuild, identify, and modify differentials and axles: Differentials: Identifications, Restoration and Repair. Jim wrote this book in conjunction with Randy Lyman, owner of Randy's Ring & Pinion. Jim is a well known and respected book author and the book is full of great information. I just checked, and one source of availability is Or they are available from Randy's (800/292-1031,

Question: I have an '05 GMC 1500 Sierra 4x4 Z-71, which came stock with 265/70R17 tires and 3.42:1 gears. I recently changed the tire size to 285/70R17 and also changed gears to 4:10:1. The shop that changed the gears recommended a Hypertech programmer to fix the odometer and the ABS light. I purchased a Hypertech and it did fix my speedometer, but it didn't fix the ABS light-the "Service Brake System" error code is still coming on. I called Hypertech, and the tech guy said that the programmer wasn't going to fix my problem.

After the programmer didn't work, I called GM. The guy told me I needed to change my cluster. This seemed a little strange to me, so I am seeking advice for a better solution.

Answer: Greg Hooker, parts manager for a Colorado Chevy dealership, offers the following:

"I would take the truck to the dealer and have them scan it and find out what is setting off the code. If the code was set off by false information from the tires and gears, and the Hypertech corrected that info, the computer should reset itself after so many key cycles.

"You may have another problem or possibly haven't completed enough key cycles to clearthe code. I'm not sure about the cluster exchange, as these vehicles are getting more and more complicated."

Question:I have asked several service departments at various dealerships and have gotten contradictory answers. My '02 GMC Sierra 2500 HD 4x4 has the 6.0L Vortec with about 180,000 miles. I am curious if it is possible to drop in an 8.1L with the Allison five-speed tranny when the time comes. Your thoughts?
Shawn Newton
Birmingham, AL

Answer: I don't see any reason why you couldn't make the swap. However, you'd better have a bucketful of gold coins. Not only will the engine and transmission be costly, but the transmission uses its own computer to "talk" back and forth with the engine's computer. This means lots and lots of wiring changes. It's not something that I would want to undertake, but sure, it could be done.

I think that you would be money ahead to just sell the truck and buy one with the larger engine and transmission. My second choice would be to rebuild the motor you have when the time comes, and perhaps add a few performance-enhancing aftermarket items such as headers and an exhaust system.

Question:I have a '93 Jeep Wrangler YJ, and was changing the oil when I discovered water droplets on the dipstick. What are the possible causes? What solutions do you recommend?
Zach Cook

Answer: Possible causes? Could be a number of things: A cracked valve seat, a cracked cylinder head or engine block, a leaking head gasket, or just plain-old condensation from not driving the vehicle long enough to get the oil hot enough to burn off any moisture that has collected from short hot and cold cycles.

My guess is the latter because you are only seeing water drops on the dipstick and not a milky yellow color in the oil. My second guess is that you'd checked the oil after just a short trip where the engine never came up to operating temperature-or if it did reach temperature, it didn't stay there very long.

What happens is when the engine is warm and you shut it down, during the cooling process, cooler and moister air is pulled into the engine where it condenses on the sides of the hot engine, or in your case on the dipstick. There have been some cases where a very small crack develops under the valves' exhaust seats and the head castings around the valve guides.

If you're convinced that the moisture is not coming from condensation, then I would suggest you try a quality block sealer. Chances are it will solve the problem, and it's a lot easier to do than pull the head and weld up the crack. My favorite brand is K-W Block Seal. Be sure to follow the instructions.

Question: I have a '96 Bronco and I installed rear revolver shackles. Should I install a traction bar in the rear? If so, where are the best anchor points for it on the chassis and the differential? For traction bar, I mean the bar that goes along with the leaf springs.
Jose Ortiz Gonzalez
Uruapan, Michoacan

Answer: If the springs are correct in design, and you're not using an excessively large tire combined with lots of horsepower, then a traction bar most likely is not needed.

Adding revolver shackles to the rear springs may cause some unseen problems. Funny thing about revolvers is that on some vehicles, they work great, and on others they cause all sorts of handling problems. A lot has to do with the suspension geometry, including the height difference between the front and rear spring mount locations.

I run them on the rear of my own flatfender Jeep using reversed Cherokee XJ 6-inch lift springs from Rusty's Off Road. I like the heck out of them. Maybe it's the reversed spring (short half to the rear instead of forward), the mounting angle, or whatever, but they work just great.

Keep in mind, to get the full amount of suspension articulation out of them; you're also going to need longer shocks, which also means new shock mounts. Now if you really need the traction bar to control axlehop, then the revolvers may not be of any benefit. Traction bars, unless they are properly designed, somewhat limit articulation-enough so I think that the revolvers won't open up like they are designed to do.

If you plan to build the bar yourself, then I suggest you take a look at the bulletin, as I am sure there is something here that will be of help. Superlift, Fabtech, Pro Comp, and several other suspension companies offer traction bars that would simplify building your own.

Question: I have a 4x4 Dodge 3/4-ton pickup with the 360 V-8. After adding a lift and 35-inch tires, even with a 4.10:1 gearset, I feel a big loss in power. Besides that, the fuel mileage sucks. I would really like to improve the performance, especially down in the lower rpm range as well as the fuel mileage.

I remember reading in a past issue on something that you wrote about headers. You said that on small-block engines, leave the short-length, large-diameter tubes to the racers and use very long tubes with a small diameter (in the 1.5-inch range). Besides that, living in the Great Lakes region, where they put salt on the road, I want something that will last and not have to be replaced every couple of years. I've looked at all the major manufacturers and it seems that the only headers that are available are short-length, big-tube designs. Do you have any recommendations?
Jim Akers
Detroit, MI

Answer: You're right-long-tube headers for the Dodge truck just don't exist. Mainly because there just isn't enough room for them due to chassis design. I had a set of so-called "brand name" headers on our Project Rammit and I just wasn't impressed. They were short and unequal and didn't gain all that in performance or mileage, and the coating on them peeled off within the year.

I did some checking and it seems that L&L Products (972/475-5202, has a set of headers with 1.5-inch primary tubes that are about 20 inches long. OK, they're not really long enough, but about the longest I could locate. These aren't your mass-production, 18-gauge, low-buck headers, but use 14-gauge tubing, 1/2-inch-thick flanges, and are Nickelshield-plated. These are covered by a lifetime warranty for not only workmanship but rust-out. By the way, L&L are the guys who make the great 460 Ford motor swap kits, and they do have some really long primary tube headers for most of their conversions.

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