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August 2012 Techline Tech Questions Answered

Differential Internals
John Cappa | Writer
Posted August 1, 2012

Axles, Wheels, Springs, and More!

Differential Dilemma
How do I tell what differentials and gears I have in my ’89 Jimmy fullsize? Is it alright to put lockers in the stock axles?

To figure out what gears and differentials you have in your truck you have a couple options. If you think the axles are stock you can take your VIN number to the dealership parts counter and they should be able to tell you what is in the axles. If you think they have been modified you’ll generally have to pull the diff covers to find out what differentials and gears are in the axles.

In most cases you can put lockers in the stock axles as long as you don’t drive too aggressively and you stick to moderation when selecting tire size.

Favorite Fords
Do you know of any website that specializes in older trucks? I have a standard cab, longbed ’78 Ford 4x4. I have been looking for custom bumpers and things you can get for the newer trucks today but I want to know if they make any for older trucks like mine.
Tyler Barnes
Cottonwood, AS

Jeff’s Bronco Graveyard ( is a great place to start.

Wagon Wheels
Will the wheels from a ’05-up Ram Power Wagon fit on an ’84 Dodge ¾-ton?

Yes. All of the older eight-lug ¾- and 1-ton trucks use an 8-on-6.5 lug pattern, same as the ’05-up Ram power Wagon.

However, be sure to check for clearance on steering arms, brakes and so on. The Power Wagon wheels have 6 inches of backspacing so they will tuck in pretty far. Since they are 17s, they may be big enough to supply the clearance you need.

10-Bolt Blunder
How large of tire can a stock 28-spline GM 10-bolt front axle live with? What are the best options for an upgrade and what is most likely to break? I would like to run a locker and 38-inch tires. Do I need to swap in a Dana 60 or can I build up the 10-bolt?

Is it possible to successfully run a 38-inch tire on a 10-bolt front axle with a locker? Yes. Would I recommend it? No.

The biggest factors to consider are your driving style and the kind of terrain you plan to attack. If heavy rocks or lots of wheelspin (mud and steep slick climbs) are planned then don’t waste your time with the 10-bolt. You will be throwing your money away. Your best bet is to upgrade to a GM 1-ton Dana 60 front axle. Good news is that it’s pretty much a direct bolt-in swap.

Now if you only plan on mild trails you can give the 10-bolt a shot, but if that’s the case do you really need a front locker?

Max Gas SUV
I need to be able to tow a 4-ton armored vehicle with the appropriate trailer using a 4x4 SUV. I’m looking for a used vehicle, between the years 2000 and 2005 with a gasoline engine. Do you have any brand/model suggestions? Towing capacity suggestions? Engine size suggestions? MPG is not a concern.

If it has to be a gas SUV you have two options: The Ford Excursion with the V-10 and the ’05 GM Suburban 2500 with the 8.1L and 4.10:1 gears.

The Excursion maxes out at 11,000 pounds tow capacity when optioned properly. Look for the 6.8L V-10 gas engine.

The Suburban 2500 should have a tow capacity in the neighborhood of 12,000 pounds when optioned properly.

With an 8,000-pound towed vehicle you’ll want to find a 14,000-pound trailer. One of these will weigh about 3,500 pounds. So you need a rig that can haul 11,500 minimum. With that kind of capacity requirement you are reaching into the 3/4- to 1-ton vehicle segment. You might want to consider a crew cab ¾- or 1-ton pickup.

Loose Hose
Where does the hose go that’s on top of the output housing on an NP208 transfer case? When I bought my ’86 Dodge W150 this hose was tied off in the engine compartment.

It’s just a breather hose. Keep it above the depth of any planned water crossings.

Wheel Wonderings
I have a stock ’06 4x4 Toyota Tundra four-door with a V-8. It has factory rims and tires on it now. I added a leveling kit to the front and new shocks all around. I would like to install bigger wheels and tires but do not want to add a lift kit at this time. Any ideas on what size wheel and tire I can go up to and still be able to turn the wheels without the tires rubbing on something? Also, steel vs. alloy? Why one over the other, if both are available in the same color and style.

With a leveling kit you can typically upsize your tires one to two sizes.

Stick with aluminum wheels. They are lighter. Less rotating weight means better fuel economy, acceleration, and braking.

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