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September 2006 4x4 Tech Questions - Nuts & Bolts

Posted in How To on September 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.

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

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I have an '84 CJ-7 and am putting 1-ton running gear under it. Should I use a GM Corporate 14-bolt full-floater axle assembly or a '99 Sterling 1-ton axle from a Ford? Which axle assembly would you recommend? I am running a Chevy 350 and 36- to 38-inch tires.

Answer: Go with the 14-bolt over the Sterling even though they are very similar. Both the 14-bolt and the Sterling use a 10 1/2-inch ring gear. However, the 14-bolt uses three pinion bearings where the Sterling uses only two, and the 14-bolt has a 1.575-inch-diameter pinion shaft versus the Sterling's 1.343-inch. The low gear ratios available for both are 4.10, 4.56, 4.88, and 5.13, but the cost of parts and installation should be less with the 14-bolt. Though the '99 Sterling comes with disc brakes it also uses a Ford-only 8-on-175mm bolt pattern and odd 14mm/1.5 coarse thread pitch on the studs, where the 14-bolt uses a more common 8-on-6.5-inch and either a 9/16-inch or 14mm/2.0 thread pitch (if you are using a front Dana 60 from other than a '99-and-newer Ford, it probably has the 8-on-6.5 bolt pattern). Both use 1 1/2-inch axleshafts but the Sterling is 35-spline where the 14-bolt is 30. The 14-bolt has been around longer and came in many different variants than the Sterling, though I would recommend a narrow version from under a flatbed truck for your Jeep project. When measured from the centerline of the axletubes to the bottom-most point on the differential housing, the Sterling does offer a full inch more ground clearance than the 14-bolt. But the 14-bolt has the tubes welded into the housing where the Sterling tubes are held in place with giant spot-welded pins. These won't be a problem with your 36- to 38-inch tires, but we have seen them break under massive diesel trucks. All in all they are very similar, but for value and commonality go with the 14-bolt. However, if you are planning on using a front axle from a Super Duty, then go with the Sterling.

I have an '03 Dana 60 front axle from a Ford Super Duty with 4.30 gears. I want to know how to make this axle compatible with an earlier Dana 60 or 14-bolt with 8-on-6.5 lug pattern. I have been unable to locate a Sterling rear-end that is compatible. Does someone make axles to swap out on the older units or can I change the rotors on the metric Super Duty 60 to match?
Loretta Schwarz

Answer: Nothing makes us more irate than when automakers screw with lug-nut patterns! It's simple: Give us 5-on-5 1/2 on 1/4-tons and all Jeeps, 6-on-5 1/2 on 1/2-tons, SUVs, and all Toyotas, or 8-on-6 1/2 on all 3/4- and 1-tons. Quit making things harder just for the sake of being different!

You have two options. You could find a matching Sterling rear axle with the bolt pattern you want and keep the 8-on-175mm unit bearing assemblies on your Super Duty front 60, but the unit bearings are known for not lasting under high-mileage vehicles and are costly to replace. However, some wheelers we know like the unit bearing for ease of removal and service.

Or you can talk to the folks at Dynatrac (714.596.4461). They offer a unit bearing to rebuildable hub and spindle-bearing conversion for both Fords and Dodges. Since the Dodge kit is 8-on-6.5-inch and the Ford is 8-on-175mm, they should be able to come up with a kit that converts the Ford Super Duty to 8-on-6.5.

I own an '03 Chevy four-door ZR2 Tracker and I can't find any information on modifying this 4x4. Where can I find a lift kit and winch bumper for my mini 4x4 SUV?
David Brooks

Answer: The Tracker and Sidekick market is growing rapidly with suspensions available through Old Man Emu (425.264.1391) and Calmini (800.345.3305) as well as solid-axle conversions coming from Trail Tough (877.789.8547) that use a Toyota front axle to replace the independent front suspension. Trail Tough also offers a front locking differential as well as 4.2:1 low-range gears for your transfer case if you have a manual transmission. If you want to change differential carriers, you can get low gears in the 5.12:1 range, as well as Detroit, Lock-Right, and ARB lockers. As for bumpers, Trail Tough, Calmini, and Shockworks 281.440.0063) all offer, or are developing, a Tracker/Sidekick bumper.

I have an '81 GMC 1500 4x4 with a 350 V-8, five-speed manual, 6 inches of lift, and 37-inch tires. This truck is driven on and off road as well as used to tow a boat. With the price of fuel rising I am considering putting a Chevy Duramax Diesel under the hood. Can I do this with minimal effort? And who can I call to find the pieces to complete this conversion?
Kelly Osborn

Answer: Unless you consider cutting up your frame, fabricating motor mounts, figuring out exhaust and cooling issues, and then wrestling with the headaches of the Duramax computer system, we would say no, this is not an easy swap. Some of the problems are that these engines have not been out long enough and they are only just now becoming available in wrecking yards for people to even consider this swap, much less offering kits to the public. However, on the plus side, folks are looking for diesel swap options every month, and with the great performances coming from modified Duramax diesels in their original vehicles, it is only a matter of time before someone starts doing these swaps commercially for older trucks. If you think the price of gasoline saved is going to pay for this swap, you are dreaming, but if you want to build a cool truck and are willing to innovate and break new ground, then let us know how you did it and we'll pass it on to others looking for that info.

I have an '88 Toyota 4x4 pickup and the bed is rusted. I want to replace it but it's hard to find one here in Michigan. I was wondering if I can use a newer model and what kind of modification I need to do. I need help before somebody reports me to the homeowner's association. I also need to replace the gas tank. It's all rusted inside and is clogging my fuel pump.

Answer: First things first, go get yourself voted in as president of the homeowner's association, and then if any complaint letters come in about you they can be conveniently lost.

As for the bed, contact the Toyota crew at California Mini Truck (909.622.1381) and All Pro Off Road (951.658.7077). CalMini explained that the '89-'95 truck beds should bolt on, but the body lines will look very goofy. However, they do have clean fuel tanks in stock and can supply you with a replacement if need be. Another option is the All Pro flatbed kit which is a bit better suited for wheeling, includes a rollbar for safety, can be outfitted to run taillights, and depending on your local laws could be street-legal.

I'm confused about what oil to use in my '94 Suburban with 101,000 miles on it. It has a 454 and an auto tranny. Should I use regular oil, which is on sale at around $0.79 per quart, or a more expensive high-mileage oil which is touted for vehicles that have more than 75,000 miles on them? I have used the cheaper varieties for years on vehicles from new to well over 100,000 miles. Is the more expensive stuff worth it?
Ray Foster

Answer: This is such a good question that it deserves the Tech Question of the Month prize: a new Currie tire deflator for airing down your tires when headed off-road.

Unfortunately, we don't have access to the type of testing facility required to scientifically determine the value of high-mileage oils versus regular oil, so we can't give you an answer that you can take to court and argue. However, here is the reasoning we use when buying oil. First, do cars seem to run any longer now compared to back before these special oils were available? Not really. In fact, if you drive reasonably, don't abuse your vehicle, use the recommended weight oil, and change said oil and filter every 3,000 to 7,000 miles, you should be able to drive any vehicle well over 100,000 miles. The technology of engines have made them less dependent on maintenance and more resilient to wear, but even so the special oils are but a small part of that longevity.

On the other hand, here are just a few of the things these oils claim to do:
Restore engine performance and power
Prevent engine leaks and oil consumption
Protect worn engine parts
Reduce oil consumption through evaporation and leaking engine seals
Increase cylinder compression
Resist oil-related spark-plug fouling
Resist intake valve deposits
Protect engine parts found in high-mileage engines from wear and harmful deposits

It's seems to us that if an oil could do all these things you would want to start putting it in the vehicle from the first day you bring it home from the dealer.

Imagine how much better it would be! In fact, you would think that it would actually increase the power and performance of your ride. Does it indeed do these things? We haven't tested it, so you are going to have to decide. Do you run the oil that is working just fine for you, or do you spend the extra money for oil that is at least as good as what you run now and could be better? Do you go with the security and financial reward of running the cheap stuff that has worked for years, or do you invest a bit more to get an oil that may indeed help clean and refresh the seals in your engine, but might also be a sales pitch for rebottled regular old oil.

My project vehicle is a '78 fullsize Bronco. I plan to build it around a race/trail vehicle with the ability to still have some street use. I have a 460/C6 combo that I am going to install in it and am planning to install an NP208 transfer case. My planned tire size is 38.5-11-15 Boggers. I am looking at putting 3.73 in the front but no one makes a 3.73 for the 9-inch rear. Since I am planning to run the same tire size on the front and rear, how much of a different front/rear gear ratio is safe to run so I am not scattering drivetrain parts every time I drive?

Answer: We understand your logic of running a 3.73 gear since the 460 should have plenty of grunt for getting the truck moving. Since the C6 has no overdrive, the higher gears will keep it from revving to the redline on the highway. As a rule of thumb, don't go more than .03 points in gear ratio difference unless you always run different tires to protect against binding. We found 3.75 Ford 9-inch gears and they should be just fine for your truck.

I have an '87 GMC 1/2-ton 4x4 with a TBI 305, manual transmission, and a NP208. The transmission is not the desirable SM465 but rather another four-speed with a high First gear ratio and an Overdrive. I pride myself on knowing every engine, transmission, transfer case, and differential out there, but this particular one eludes me. I remember a tech question many years ago in some 4x4 rag about an overdrive tranny like mine that may have been put in some GM diesels. They tagged it an NP833. Could this be it? Also, the reverse in my tranny is up and to the far left. This thing must be rare so I will probably yank it for a milder project down the road that may see some road time before I break it.
Justin Baker

Answer: The crew at All-Trans transmission parts verified that you do most likely have an NP833, also known by GM as an MY6. The case is usually aluminum, but was available in cast iron. First gear is 3.09:1 followed by 1.67:1, 1:1, and .74:1 overdrive. These cases were found in light-duty GM trucks and vans between 1982 and 1987 as well as some Chrysler vans and trucks between 1976 and 1985, but never behind a big-block or a Cummins diesel. The major issues with this transmission involve failure where the counter gearshaft goes through the case, but if your case is not leaking from the front of the case it is probably fine. To make it last, do not put the truck under excessive loads while in overdrive.

My wife has a '94 Dodge Ram 3500 four-wheel-drive dualie. We would like to put larger tires on it because the stock ones are too small and look silly. Is there a safe way of doing this so the rear tires don't rub, overheat, and blow?
Matt Nagy

Answer: I'm also a fan of the big-butt look, and I'm not talking about your wife, who I'm sure is gorgeous, but rather a dualie with big ol' muddy tires. The best way to make big tires fit under a dualie is to have custom wheels made. One source to have that done is Taylor Made Wheels (323.567.3998), but if that is out of your price range, contact Off Road Unlimited (818.563.1208) about its dualie wheel spacers. ORU offers a kit made of billet steel for strength. When installed between your inner wheel and outer wheel the spacers keep the tire sidewalls from rubbing and getting hot. Even still we would recommend a set of tall skinny tires for this type of truck.

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