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April 2008 4x4 Tech Questions - Techline

Posted April 1, 2008

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Four Wheeler
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Question: I need some help with a discbrake conversion. I purchased a '71 Bronco, and I'm trying to turn it into a functional trail vehicle. One of the things I want to do is convert the brakes from drums to discs. It has a Ford 9-inch in the rear and a Dana 44 in the front.

Everyone and their mother wants to sell me a kit to do this for several hundred dollars, which is more than I want to spend. Do you know how I can do this on the cheap? Which over-the-counter rotors and parts could I get and make work with the appropriate brackets or with a little fab work? I know I can not be alone in this, as the Dana 44 and Ford 9-inch are way popular.
Brian Wensel
Fort Mohave, AZ

Answer: I will have to agree that those early Bronco brakes leave a lot to be desired. A disc-brake conversion is not cheap, no matter how good of a scrounger you are. Brakes are a pretty important item, especially when your life depends on them. However, with a bit of forethought and maybe some luck in finding the parts, you can do the conversion without too big of a dent in your wallet.

The easiest way would be to obtain the complete front end and/or brake system from a '76-'77 Bronco. The chances of finding such are slim to none, and if you do get lucky, it's going to be pricey. So let's settle for second best.

There are several ways you can do the front conversion, but this seems to be one of the better ways. Starting out, you can't use the original master cylinder, so you will have to obtain one from a '76-'77 Bronco that was originally equipped with disc brakes, along with hubs and rotors. Then you're going to need a bunch of parts from a '74-'75 1/2-ton Chevy pickup or Blazer. Yes,said Chevy-sorry about that, Ford purists. This will include the spindles, calipers, backing plates, and a bunch of small parts. Take a look at node/73 and it will outline just what is necessary to make this all come together.

For the rear, things are also pretty easy. Rock Equipment (916/434-7887, sells some brackets you can use, and then you come up with your own parts, or you can buy the parts and pieces directly from them. Having an emergency brake is not only a necessity but the law, so keep this in mind when doing the rear conversion.

Keep in mind before you start on this kind of a project it is going to set you back a considerable amount of money to do it right, but there is only one way to do brakes, and that is the right way.

Question: I just recently bought a '99 Jeep Wrangler Sport with the threespeed auto tranny. It has 31x10.50 BFGoodrich A/T tires on it. It's not a daily driver, but when I do drive it to and from work, it chugs the gas. The last time I filled it up, I got 12 mpg. I looked at the original window sticker and it said it should get 15-19 mpg.

I plan to put the K&N filter on it, but I really want to get the revs down at highway speeds to help reduce the wear and tear on the motor. It only has 48,000 miles on it. The traf-fic flows between 75 and 80 mph to and from work. Is there a bolt-on overdrive that I could put on it? If so, about how much do they cost, and what are the pros and cons?
Brandon Spell
Silsbee, TX

Answer: Yep, your Jeep probably should be getting a lot better fuel mileage than 12, but not at 80 mph. To start off with, just because others are driving at 80 mph doesn't mean you have to. Have you ever thought about leaving for work, say, 10 to 20 minutes earlier and driving at a steady 60 to 65 mph? My guess is that your fuel mileage would then be about 18 mpg.

Oh, and something to keep in mind is that you can't figure fuel mileage off of just one tank fill-up and be accurate. Different nozzles shut off at different percentages of tank fullness. Even the air temperature can affect when the nozzle shuts off. Just a gallon more, or less, than the last fill-up can make a big difference when figuring fuel mileage.

An overdrive would be a great improvement, but unfortunately there is not a bolt-on unit for your Jeep's three-speed automatic or behind the transfer case. Gear Vendors (, 800/999-9555) lists one for the Dodge 203 transfer case (similar if not the same as the one in your Jeep), so you might want to contact them to see if your application would fit, which I am sure it would. The problem is that the overdrive unit is quite long, which would make for a very, very short and impractical-length driveshaft. Even so, you would have to drive a heck of a lot of miles to get any payback, as the price installed would most likely be in the $3,000 to $4,000 range.

I think that the best thing to do would be to swap in an AW-4 four-speed overdrive automatic from a Jeep Cherokee. This is a very doable swap, but how much it would cost depends on just how good of a deal you get on the AW-4 and how much of the work you plan to do yourself. My guess is when it's all said and done, if you do the work it would be under $1,000. Under Google, I typed in "TJ transmission swap" and found several Web sites that could lead you through the process.

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