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July 2006 4x4 Tech Questions - Nuts & Bolts

Posted in How To on July 1, 2006
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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:

Upside-down Diesel
I read the article on vehicle preparation after a trail rollover ("Hang On" Apr. '06). You mention that before starting the engine the spark plugs need to be removed and the engine turned over a few times to relieve the cylinders of oil that might have bled past the rings. How would I handle that concern with a diesel?
Milwaukee, WI

A diesel engine has just as much chance for oil to leak by the rings and into the combustion chamber as in a gas engine during a rollover situation. In fact, most diesel engines need that oil to help lubricate the skirts of the pistons so they might even have a larger gap in their ring than a gas engine. In the case of a rollover with your diesel 4x4, the easiest step would be to remove the glow plugs, as long as they are inserted directly into the combustion chamber, and crank it over to make sure no oil is in the cylinder. If your diesel doesn't have glow plugs threaded directly into the combustion chamber, you can either remove the injectors if they are threaded into the combustion chamber or pull the valve cover and put a small shim or screwdriver between your exhaust valve and rocker arm. Then turn the engine over by hand with a large wrench or socket on the crank. I don't see many diesels on the trail, but with the torque and run-at-steep-angle attributes these engines offer, they make great backwoods vehicles.

Since this question had the whole staff scratching our skulls, I decided to award it our Tech Letter of the Month. Elsewhere in this issue you can read about our recent trip to Florida, and I'm sending you a copy of the Trucks Gone Wild videos showing big trucks (some diesels) sled pulling, mud bogging, having tug-o-wars, and even floating a monster truck across a lake! For anyone else interested in these videos check out on the Web.

Hunting Diesel in the Yukon
I have a '96 Yukon and have had numerous problems with the 350 engine and transmission, plus it has more than a few miles on it. It is used primarily as a daily driver to mild hauler and occasionally sees some dirt. I would like to swap in a diesel in favor of the current 350. I am not, however, looking for a torque monster as much as a reliable means of upgrading the drivetrain. I am leaning towards the Cummins for its reliability and reputed gas mileage, but know little about the requirements for this kind of swap. I suspect that the suspension, frame, and drivetrain will need to be upgraded, but other than that I have no direction. Is it even physically possible?
Nathanial Backes

You have hit on a popular swap idea. Diesel power is hot these days, but swapping from a gas engine to a diesel engine, especially in a 1/2-ton truck or a Yukon, requires lots of work. With the current price of diesel fuel surpassing that of premium gasoline, we are not really convinced of the financial argument for the swap. And remember that in the state of California any engine swap must be done with a same year or later engine as the vehicle being swapped into, so check your local laws. I discussed this job with Bryan McCully of Fabworx Off Road (707.566.7045) in Santa Rosa, California. He just finished a similar swap into his own '96 GMC truck, but he didn't make any claims that it's not a lot of work.

My first piece of advice is to go with an Optimizer 6500 from General Engine Products ( It has a Chevy bolt pattern and would be an easier swap, plus some versions push around 300 hp. If you are set on the Cummins route, I'd recommend looking for a '94 to '97 Dodge Cummins 4x4, as these 12-valve engines come with the later-version fuel pump that has more aftermarket upgrades available and have endless possibilities for power, while not being computer controlled like the current 24-valve. You would be better off getting the entire truck including the transmission, transfer case, and heavy-duty axles since your stock parts will not stand up to the torque output of the Cummins. In the end only the body and frame of your Yukon would be reused. That frame is not even stout enough to deal with the engine's robust power, though plating and stiffening with some properly attached tubework is another option. So plan on a body lift, a solid-axle swap, a full drivetrain swap, a fuel system upgrade, and a monetary outlay that will take years to justify based on fuel economy. Plus electrical components like your speedometer and gauges may need a complete rework if you want the stock style dash. Is this swap possible? Yes, and it has been done before, but you have to be really married to the Yukon body style to justify it. Nonetheless, I want to see it first when you're all done. For more information, check out these Web sites,,, and

Wanted: Cheap Truck
My uncle gave me his '87 Sami a few years ago. I had it for six months and had to sell it. I've missed it ever since. Now that I'm a little older (24) and have a decent job, I can afford to get another and trick it out. I have the Sami bug real bad. I'm not looking to spend a lot. It has to be a budget wheeler, and I also want to use it as a second commuter car. I'm having a hard time finding one that is in decent condition for a good price. I don't really want to spend $1,500-$2,000 for a beater. How did you find one for $450? And a '91 with EFI at that? I don't mind if it has miles or whatever. I plan to motor swap down the road to give me a better chance to pass smog, plus a little more kick to wheel better. Any help you can give would be great. It's going to eat at me every day until I get one. I can't wait to take it to the desert.
Matthew Kaluzne

I've been experiencing the exact same problem. I went to check out an old flatfender Jeep that wasn't exactly pristine, but the owner had seen some other old Jeep go for $10,000 on eBay and was sure that his was worth the same. I know that there are some good deals on the Internet, but some folks are out to make a quick buck on others' ignorance.

The trick to finding a good deal is looking for trucks that previous owners no longer want to deal with. Start driving up and down back alleys, around gas stations, and even past parking garages. What you are looking for is a four-by that looks a bit derelict, dusty, and sitting low on a flat tire or two. Then it is time to do some acting. Even if the vehicle is not showing a "For Sale" sign doesn't mean you shouldn't knock on the front door. My favorite pickup line goes like this, "Hello. A friend told me there was an old Samurai [or Jeep, Toyota, and so on] for sale around here. Is the one in your driveway perhaps for sale?" Oftentimes the owner either says yes it is, or is willing to give you his phone number in case he might want to think about it. However, if he says no, ask him if he knows of a similar rig for sale, as owners of certain models often know where to find more.

Another great method to find a good deal is start telling folks what you are looking for. Both of the Samis I brought home and most of the other rigs I've owned were found by just telling lots of friends and some strangers what I wanted. It's amazing how 4x4s start coming out of the woodwork when you have more than just your two eyes looking. It doesn't hurt to ask friends that work as parts countermen, garbage men, police officers, and tow truck drivers, as they all get around a lot and might just find your next project. Finally, go check out the local junkyards and charity vehicle sales lots, as both can be hiding your next deal. In fact, the best way to find a cheap deal is to shut off your computer and get out there hunting the back roads.

I've had an '87 Samurai on 31s for just a little while and have already busted my itty-bitty front axle. I was wondering how Tim Hardy was able to keep his axles alive running 35s (someday I would like to play with 35s). If you could tell me how to do what he did or anything else that would add a little beef to my stock axles, I would appreciate it.

Tim Hardy has been along on many of our Ultimate Adventure trips and though his Suzuki Samurai looks hammered, he rarely spends time fixing the axles. The biggest factor to his axle survival is his driving style. He rarely, if ever, uses excessive throttle, and if he gets in a situation where the tires start to bind, he quickly backs out and tries another line. Plus since his Samurai is so small and light (not to mention Hardy himself) he can usually crawl obstacles that other, heavier vehicles need to throttle up.

Even with that said, Hardy did make some trick upgrades to his axles, and would be willing to do it for others if they wanted. The front axle uses a stock carrier with an EZ locker and rear-axle side gears to get 26-spline inner axleshafts. Then he sourced some 5.12 gears out of an '89-'96 Geo Tracker or Sidekick with some special mods to keep the cross shaft in place. Running from this front locker are some 4340 chromoly axleshafts from Dutchman that have a 26-spline inner end and a 27-spline outer end. That 27-spline end runs into a Subaru 87LAC Birfield from a '79-'83 turbo Subaru wagon front end. These Suby Birfields have cups that are much larger than stock Samurai units, but Hardy had to cut and weld new stub shafts onto the cups to match the stock outer Samurai hubs (this is a step where his experience as a machinist and welder pays off). Finally, in order to get these new larger Birfields into the axle, Hardy has to completely remove the knuckle and even then it's a bit of a struggle to get them in.

In the rear Hardy uses a Sidkick centersection, again with 5.12 gears, but this carrier is stuffed with 31-spline Ford truck side gears that are specially machined to fit in the carrier. Again a Detroit EZ locker is used, and it amazingly meshes with the machined Ford gears. Finally, the side-gear bore is milled out and Ford thrust washers are used.

The final step to Hardy's long-living axles is the proper break-in. After the initial setup, Hardy drives 3 to 5 miles and lets the axle cool down completely, then 5 to 15 miles and another cool down, then 15 to 30 and again let them cool. After that he changes the oil and checks the gears for any heat issues or discoloration. Then after 200 miles he checks the oil for any large chunks of metal. Then it's normal driving for up to 300 miles and then at 500 miles he changes the oil to a high-quality synthetic and he's ready to go wheeling.

If all this is up your alley, you can get a hold of Tim Hardy at 530.642.0436. Otherwise, I'd recommend Trail Tough (877.789.8547), Spidertrax (800.286.0898), or CV Unlimited (800.868.0057) for some Suzuki axle upgrades.

Don't Be Anti-AMC
I want to swap a 283 into my '75 CJ-5 Jeep and I'd like to know if this is a good swap. My Jeep has an AMC 304 in it now but parts are hard to find for it. If this is a good swap, what will I need to make it work? I have a T-15 three-speed. I only have 33x12.50 TSL Super Swampers and open diffs. Mud and clay are what I will be mostly using the Seep for, and driving to work sometimes.
James Ehlers
via e-mail

I'm sure you are considering swapping in the 283 since it is a GM engine and most GM V-8 parts are ultra common, but even so I'd keep the AMC 304. AMC parts are not all that rare, and the aftermarket has many options for upgrading this engine. Edelbrock (310.781.2222,, for example, has heads, intakes, and complete fuel-injection systems. The time and money involved in swapping in the 283 will pale in comparison to a few solid AMC upgrades. Plus, you would also be going to a smaller engine and that is not what you want for the mud.

Always Locked?
What is the safest distance you can drive on the street with your front hubs locked?
Ricardo Rodriquez
Fort Payne, Al

Locking hubs were designed to help fuel economy, reduce wear and tear, and resist front driveline vibrations, but driving on the street with your front hubs locked while in two-wheel drive is not necessarily bad. When you lock the selectable hubs it attaches your wheel, tire, and hub assembly to the axleshaft. This in turn causes everything within the axle and your front driveshaft to rotate, but it is being turned from the tires, not the transfer case or engine. If your front driveshaft has no balance or angle problems, then you shouldn't notice any vibrations, and other than a slightly increased wear on your steering and driveshaft U-joints, carrier and pinion bearings, and the seals on your axle and the front output of your transfer case, you should be fine to drive down the highway with your hubs locked. However, having to turn all those parts will also reduce the fuel economy of your 4x4. If it were up to me I would get out and unlock the hubs.

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