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August 2006 4x4 Tech Questions - Techline

Posted August 1, 2006

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Question: I have an '80 CJ-7. A friend gave me a GM 14-bolt rear and a Dana 44 front axle out of a late-model Chevy. Plans for an AMC 360 and a TH350 are also in the works. I would like to use my springs, but I'm worried about axlewrap. Should I use springs out of a junkyard? If so, what kind? Would there be some kind of traction bar out there? The Jeep most likely won't see hard-core rockcrawling. I just want to hit the trails with other four-wheel enthusiasts.
Charlie Janek
via fourwheeler.com

Answer: That fella must be a great friend to just give you the axles. Yes, it is very doable and yes, you could just use your present springs. Poison Spyder Customs (www.spydercustoms.com) has a kit to do just this type of conversion. You would be money and time ahead to buy this kit, as all the engineering has been done for you already and I have always been impressed with the quality of the work. The kit includes, as stated on the company Web site, the front spring mount/reverse shackle bracket, rear shackle outboard brackets, winch-plate spacers, steering-box spacers, shackle mounting plates, as well as all the nuts and bolts needed. These plates bolt between the outboard brackets and the spring hanger to allow full shackle movement. The front spring bracket has a 1/4-inch gap between the frame to allow for winch-plate brackets. If you don't have a winch, then these brackets fill the gap. A CJ's steering-box support bolts to the original front spring hanger.

Question: I have an '87 Bronco II and I just got a Dana 44 and a Ford 9-inch from a '79 F-150 to put under it. Now that the U.S. government has blessed us with tax returns, I can finally rebuild them. I want to run 5.38:1 gears, which are actually 5.38:1s for the 44 and 5.42:1s for the 9-inch. I've been told that seeing as how it is pushing the border of .05, I should go with a different ratio.

Though the truck will never see the pavement, I do have the stock drivetrain (weak!). Second, I want to install a locker with a new stronger carrier in the Dana 44. The guy I am trying to order them from is telling me that the axle is too weak for a locker and I need to go with a Detroit Truetrac.

I really don't want to be doing any fancy brake work to get the front end to lock up. I would love to run 37-inch tires and I've been told that the axle can hold them, even with a locker, but I think that would be pushing it. But I have come to realize that I might have to run 35s which is OK too. Oh, please don't suggest an ARB-they're too pricey for me.
Clint Coombs
via fourwheeler.com

Answer: Don't worry about that slight of a difference in gear ratio. I have seen enough variation in tire height within the same brand of tires to amount to that much axle ratio variation. If your truck was a full-time four-wheel drive, that would be a worry, but not in this case. If you're really worried about the difference, you can lower the air pressure in the rear tires a bit more than the front to lower their overall height.

Your front axle should be strong enough for the 37s if you're easy on the gas, especially since the Bronco II is fairly light. In time, you could always go to some aftermarket axles. The weak links will be the axle U-joints. The real secret of keeping the U-joints alive is not to have the tire turned at a strong angle when you romp on the gas pedal.

By all means, go with the Detroit Locker up front if you want it. It's a bit harder on axles, and has some traits that make it not easily driveable on a snow-covered highway at speed in 4x4 mode. The Truetrac is an excellent unit and works great up front under all conditions. Sure, it's not as positive as a Detroit Locker, and it may take a bit of brake modulation to get it to totally lock up in some situations. In the rear, be sure you're using the larger 31-spline axle.

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