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I have a 93 bronco xlt and I'm not sure what's wrong with and I was hoping someone could help. When I engage the 4x4 I get really bad grinding scraping noises coming from underneath the truck when I move. I'm running mismatched gears 4.56 front and 3.73 rear, this is how it was when I bought the truck. My 4wheel works but the front tires lock up time to time. I've taken apart the front axle and there doesn't appear to be anything wrong inside so my next guess was the transfer case. Can anyone help me?
 

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I'm running mismatched gears 4.56 front and 3.73 rear. When I engage the 4x4 I get really bad grinding scraping noises coming from underneath the truck when I move. My 4wheel works but the front tires lock up time to time. Can anyone help me?
Yeah, stop running the truck in 4WD with mis-matched gears.:doh0715:

Transfer case sounds like it's FUBAR. Does it make noise in 2WD?
 

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Thanks 351w500
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Whats wrong with it is you have destroyed the Tcase by trying to drive it in 4WD with those mis-matched gears. Come on what were you even thinking!! You know there mis-matched but you still put it in 4WD, Not a very smart move there.
 

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Could be wrong but I'm pretty sure rhauf was running a similar or larger difference in his bronco for a while and it was holding up even with a stroker.
 

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yo,

"...Ford built our Broncos & other 4x4 trucks & vans with a numerically lower front gear ratio in the front Dana 44 than the rear so that off-road steering is enhanced. A Bronco built with 3.55 rear ratio would have a 3.54 ration in the front Dana 44; or; 3.08 in the 8.8 & 3.07 in the Dana 44; or 4.11 in the 8.8 & 4.10 in the Dana 44, etc..."; Following was in my MS WORD Notes and the source, Randy's Ring & Pinion has removed it from their current web site; The gear ratio in the front of a four wheel drive has to be different from the front so the front wheels will pull more. There have been many different ratio combinations used in four-wheel drive vehicles, but not so that the front will pull more. Gear manufactures use different ratios for many different reasons. Some of those reasons are: strength, gear life, noise (or lack of it), geometric constraints, or simply because of the tooling they have available. I have seen Ford use a 3.50 ratio in the rear with a 3.54 in the front, or a 4.11 in the rear with a 4.09 in the front. As long as the front and rear ratios are within 1%, the vehicle works just fine on the road, and can even be as different as 2% for off-road use with no side effects. point difference in ratio is equal to 1%. To find the percentage difference in ratios it is necessary to divide, not subtract. In order to find the difference, divide one ratio by the other and look at the numbers to the right of the decimal point to see how far they vary from 1.00. For example: 3.54 ÷ 3.50 = 1.01, or 1%, not 4% different. And likewise 4.11 ÷ 4.09 = 1.005, or only a 1/2% difference. These differences are about the same as a 1/3" variation in front to rear tire height, which probably happens more often than we realize. A difference in the ratio will damage the transfer case. Any extreme difference in front and rear ratios or front and rear tire height will put undue force on the drive train. However, any difference will put strain on all parts of the drivetrain. The forces generated from the difference have to travel through the axle assemblies and the driveshafts to get to the transfer case. These excessive forces can just as easily break a front u-joint or rear spider gear as well as parts in the transfer case.
Source: by miesk5
 
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