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September 2008 4x4 Tech Questions - Nuts & Bolts

Axle Units
Fred Williams
| Brand Manager, Petersen’s 4Wheel & Off Road
Posted September 1, 2008

Q I have a '79 F-250 with a 400M engine and four-speed manual transmission. The truck is lifted and has 36-inch Iroks and lockers front and rear. My problem is I burned the stock clutch up, so I put in what I was told was a better clutch and wrecked that in a couple months. Am I burning up clutches because these tires are too much for it, or do I just need the best clutch I can find?


A Have you changed the axle gears to deal with the bigger tires? Or are you shifting gears a lot when the clutch is under water and mud? If it came apart that quickly I would say it was either severely abused or a bunk part to start with (or both). I would make sure you're running low gears like 4.56 to 5.13s to help the clutch. Try not to let a bunch of mud and slop get between the clutch and the flywheel by sealing up the bellhousing and only shifting when the bellhousing is above the mud line, and get yourself a good parts store replacement. I would go to the local parts store and get the stock replacement; dunking a high-dollar clutch in the mud isn't going to get a long life out of it, so you might as well run one that doesn't break the bank if you need to replace it every 12 to 24 months from severe mud use. And remember that even breaking in a new clutch with 200 to 300 miles of moderate use is difficult to do. It will still help the clutch live longer.

Q I have an '01 Dodge Dakota 4x4, and when I put on a brushguard on, it caused the front end to sag a little. I was wondering if cranking the torsion bars to bring it back up, or even going a little higher to level it out with the rear end, was a good idea?

Logan B.

A The Dakota came with a front rake from the factory, so be sure your brushguard is added to that before you adjust the torsion bars. Adjusting the torsion bars isn't a bad thing as long as you do it in moderation. You should be able to raise the front slightly to return it to the stock rake after installing the brushguard. Just make sure you don't overcrank the torsion bar until you are hitting the droop stops and topping out (overextending) your shocks. You want the suspension to ride so the A-arms are in between the bumpstops and droop stops and the shock is in the middle range of its travel at ride height.

Q You have lost me when it comes to unit bearings. I read the article comparing unit bearings and traditional hub/tapered bearings and I thought that it was great that you gave pros and cons ("Small Wonder," May '08). You never really took a side on which was better though. Then I read the article about the custom axle for the Danger Ranger, where the "last axle you will ever have to buy" included unit bearings. What I don't understand is, why are some aftermarket companies, such as Spidertrax and Currie, embracing the unit bearing while others, such as Dynatrac, are building kits to eliminate them?


A If you look at the benefits of a unit bearing, you'll see that they are fully enclosed, they bolt on easily to the knuckle, they are light weight, and they don't require any servicing. If you look at the downsides, they are expensive, they don't last forever, few allow the use of selectable front hubs, most older versions need the axle stub shaft to help hold them together, and you can't do any servicing to them to make them last longer the way you can with a rebuildable bearing style spindle and hub.

The major automakers undoubtedly went to the unit bearing for ease of assembly, ease of repair, and the fact that just about any person, robot, or monkey could install them on an axle whereas a rebuildable hub and spindle (RHS) requires an installer who can set proper bearing preloads and not damage seals. In fact the tolerances from the current factory OEM unit bearings are so high they can hardly be matched by someone servicing a spindle and hubs.

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