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Unequal Gears in Fullsize Bronco
Q. I have a 1988 fullsize Bronco. I was mudding and broke the spider gears in the rearend, so I went to the junkyard and pulled a new one. Come to find out the rearend ratios do not match. I was thinking, "Well, what's going to happen next time I lock it in? Wouldn't it either push or pull the front end because they are not the same? Could it break the transfer case because of too much stress, or maybe the universal joints?" The old rearend was a 3.54:1 and the new one is a 3.55:1. Not much difference, but the new one is way heavier, and the gears look much bigger. To make things worse, it is sitting on 39.5 Super Swampers. It has a five-speed manual transmission. I am trying to see what I am up against with possible problems and/or solutions. I need it to be cheap because I am still in school. Would it be ok if it was only locked in on dirt or sand considering that the tires are always slipping and sliding anyways?
A. First, that little difference in gear ratio, front to back, will not make a bit of difference. Most likely, differences in tire diameter will make more of a difference in overall gearing than what you have in the difference in gears. Yes, having a different gear ratio, front to rear, is pretty common, especially when the front is a different manufacturer, model, or size. It just has to do with the number of teeth on the ring and pinion gear versus the overall diameter. If the gear ratio is radically different, like 3.54:1 and 3.73:1, then you have a problem with one axle trying to turn faster than the other. Then some thing has to give, be it tire slippage or breakage in the driveline.
Now, as to the gears in the new rearend being larger: your truck came from the factory with what Ford refers to as an 8.8-inch axle. The numbers stand for the diameter of the ring gear, 8.8 inches. My guess is that you put in a rearend out of something other than an '81-97 Ford F-150 or Bronco. If the rearend came from another Ford truck of a different year, then it just might be the more desirable Ford 9-inch. The 8.8 has a removable rear cover while the 9-inch has a complete differential that comes out the front of the housing. Some of the early Ford heavy-duty 1/2-tons also used a Dana 60 rearend, which also had a rear cover plate. If so, someplace on the housing casting you should see an embossed number "60."
Dana 60 Shoppers' Tips
Q. I am looking to build a beefier axle for my 2000 Dodge Ram 1/2-ton with the 9.25-inch rearend. I am looking for a Dana 60 rear. I'm on a budget, so I'm primarily looking for the housing first, and then I can get aftermarket parts after that. What vehicles has the Dana 60 rear been in?
Oak Grove, KY
A. The Dana 60 has been in a lot of vehicles and available with several different bolt patterns, as well as different widths and spring mounting locations. The number of applications is way too large to list here.
Probably the best thing for you to do is measure from the wheel mounting surface of one side to the wheel mounting surface of the other. Then, with this information, start your search in wrecking yards, keeping in mind the difference in the wheel bolt pattern you may find. The more common bolt pattern you're going to find is a standard 8-bolt pattern on a full-floating rearend. Any of the five-bolt pattern axles (5-on-51/2) will come from the '70s Fords, IHs, and some Dodges that had the 440ci engine package. Don't forget that you will also have to match the front and rear gear ratios.