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July 2007 4x4 Tech Questions - Nuts & Bolts

Posted in How To on July 1, 2007
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Confused? E-mail your questions about trucks, 4x4's, and off-roading tech using "Nuts, I'm confused" as the subject and include a picture (if it's applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I'll be checking the forums on our Web site (, and if I see a question that I think more of you might want to have answered, I'll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes.

Write to:
Nuts & Bolts
4-Wheel & Off-Road
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515
fax 323.782.2704

E-mail to:

Question: In what model years did Jeep use the 4.2L engine in the Wrangler and what were the horsepower and torque ratings? Also, did they "downsize" to the 4.0 or is that an entirely different engine?
T. Steele, via

Answer: Jeep has been using a straight-six engine since the '50s with various models including the 226 L-head Super Hurricane used from 1953 and then the 230ci Tornado OHC six in 1963. In 1965 the AMC 232 High Torque I-6 took over and this slowly evolved into the 4.2L 258 found in many CJs and early YJ Wranglers starting around 1972 and running until 1990. The 258 is a great engine-torquey and tough-but it was never offered with fuel injection. It was basically a stroked version of the 232 and put out roughly 150 hp and 240 lb-ft of torque. In 1987 the 4.0L straight-six was introduced and, though it had a smaller displacement, it offered more horsepower at 190 with a slight drop to 225 lb-ft of torque. This engine is commonly thought to be better than the 4.2 since most years it came with fuel injection, and is more fuel efficient, reliable, and powerful. The 4.0 stuck around until just this year when the new JK Wrangler was introduced, and the only engine available now is the 3.8L V-6.

Question: Our '90 Toyota Extended Cab 4x4 pickup is our daily driver, so stability on the highway and low road noise are important since most of the truck's life is spent on asphalt. But the reason we have the truck is that we got tired of getting stuck in the mud on our bush lot.

The drivetrain and suspension are mostly original equipment. (We live in the Rust Belt, so it's on its second body and third paint job). The 33x12.5 off-brand tires have been good in the mud and have taken us places where the other trucks get buried, but they are getting worn out. The old tires' highway manners are OK, but they are noisy, noisier than our 31-inch snow tires. What tires would you recommend that will still get us through the mud but will have good highway manners and reasonable road noise?
Peter T., via

Answer: One of the quietest tires I have tested is the Toyo M/T Open Country. These tires have great highway and dirt characteristics and I have friends who really like their performance in the snow as well. There are a lot of great tires out there, and most mud-terrain tires get louder as they get older and the miles of use increases, but I would look into the Toyos for your situation.

Question: I have a '91 GMC Jimmy that has a 14-bolt rear that I installed 4.88 gears and a Detroit Locker in about two years ago. It is my daily driver and everything worked fine until about two weeks ago, when I noticed a loud clank (it got worse and worse) every time I would put the truck from Drive into Reverse or vice versa. I crawled under it and with the tranny in Neutral. I noticed that the driveshaft had about 180 degrees of free turning play. Except for the annoying clank it seems to drive normal.

Now, I know that is a lot of play on the driveshaft and I haven't opened up the diff yet. I would like to know what to expect when I drop the diff cover, and what caused this to happen.
Gabe, via

Answer: I ran your question by Scott Frary, the aftermarket sales manager for Eaton Detroit Locker, and got the following answer:

"180 degrees of slop is excessive. The most I ever see is less than 1/3 rotation. This excessive rotation is most likely the result of many different components. Sloppy driveshaft U-joints, ring-and-pinion wear, axle and/or driveshaft spline wear, and Detroit Locker backlash all can add up to excessive lash. Regardless of the cause, I'd recommend that the owner check all of these components, including the Detroit, for damage."

Question: I work for a fire department and have recently been given custody of an '86 Chevrolet 1 1/4-ton truck from military surplus. I have been instructed to make it a forestry unit, but I have very little information on this truck since we just received it a few days ago. My chief is dead-set on converting it to a 12-volt system (more specifically, having me convert it). As I understand, all the normally replaced parts such as light bulbs are 12-volt, and the only part that I can find that is 24-volt is the starter ( which is working fine for now). What is the advantage of converting the entire system to 12 volts? Why would it be so bad to leave it alone until the starter dies and then convert the system as opposed to throwing away a perfectly good starter just because of the voltage it requires? Thanks and keep up the good work.
Justin, via

Answer: I have the exact same truck as what you are starting with, and so far I have not changed the system to 12 volts. Like yours, my truck uses two alternators and two batteries to supply 24 volts to run the starter, and then uses resistors to get 12 volts for everything else. I see you having two options, leaving the starter 24 volts and having a very strong starter to turn over the high-compression diesel engine, or changing it to a 12-volt starting system so you can get a cheap 12-volt GM diesel starter at just about any auto parts store in America. I chose the former until my starter dies (and because I'm too busy to do the swap), but even then I'll probably either get it rebuilt or get a rebuilt version from Boyce Equipment (800.748.4269). The 24-volt starter costs more than $200 and the 12-volt version costs between $85 and $185 depending on where you get it.

Another problem you might run into is that your truck has two alternators and two batteries run in series, and this results in more possible parts needing to be repaired or replaced down the road. I'm sure your chief is considering these costs in having you do the conversion, but if the truck is running fine, I would leave it alone for now. The higher-voltage starter should produce more torque for starting the truck and that alone is important if you are out fighting fires and need to get the truck moving in a hurry. I have found that there are more problems with the glow-plugs system than with the starter on my truck and modifying the glow-plug system with a manual temporary switch will probably be the best bet for you. If you do convert it to 12 volts you may find that the 12-volt starter is lacking in torque, in which case you might want to consider upgrading to a gear-reduction starter such as those made by Powermaster (865.688.5953) for the GM 6.5L or 6.2L diesel. However, the price of these is more comparable to a 24-volt military starter. There are awesome conversion instructions on the Internet at: It shows the step-by-step instructions for converting from 24 volts to 12 volts. Another great military-vehicle Web site is

I think it's a great job you are doing there and I hope this was helpful in figuring out your next step with this truck. Since you'll be using this truck for firefighting, and hopefully protecting some off-road trails, I'd like to award you with this month's Tech Letter of the Month. I know your question is a bit more specific than what I would usually pick for this reward, but I think you'll be needing the Patriot 9500 UT winch from Ramsey Ramsey Winch (918.438.2760, that I'll be sending you. It features a semiautomatic clutch that is faster than conventional self-recovery winches, and when used in conjunction with the Ramsey Patented Wireless Remote you will have near unstoppable power. The semiautomatic clutch reduces winching steps and saves operator time, and a sealed motor, drum, and gear carrier assembly protects the winch from the elements.

Question: I have an '01 Nissan Frontier and would like to make a few exterior/body modifications to my truck (things like fender flares, bars, lights, and so on), but I have yet to find a suitable Web site to find such parts for my truck. Are there any Web sites dedicated to off-roading Nissans or any place I can find quality Frontier body parts?
Lane, via

Answer: Performance Products ( offers a lot of Nissan accessories, and Nissan 4 Wheelers ( has an online Nissan community.

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