Ring and Pinion

hillbilly delux · Sep 17, 2009

If i change my 9 inch rear end gears from 350 to 388 will i need to change my stock front end gears? Bronco is 74 d 20 t case. I haven't checked to see what my front end gears are. Thanks for any suggestions or opinions!

thegreatjustino · Sep 17, 2009

Front and rear need to be the same or very close to the same (3.50 rear, 3.54 front is ok - or similar close ratio). If you have 3.50 in one and 3.88 in the other, you are going to ruin your transmission and transfer case eventually if you run it in four wheel drive.

If all you do is drive on the street in two wheel drive, your gears don't have to match.

hillbilly delux · Sep 17, 2009

Thank you sir Justin. I was thinking it would just was hoping not for money sake.

Broncobowsher · Sep 17, 2009

As mentioned, you need to change it to use 4WD.
But if you are playing around and just want to see how the Bronco will drive on the street in 2WD, you can put a different ratio in the back. It lets you try a few ratios and see what you like without changing the front again and again. But when you do get the rear where you like it, spend the money and get the front to match.

I hate even mentioning this, but you can use mixed ratios in a pinch, just extremely limited use. Sunk the rear axle in mud, front is on the street. When there is so much tire slippage that it couldn't move an inch in 2WD, 4WD for 10 feet, then right back into 2WD.

Steve83 · Sep 17, 2009

The less traction you have, the less it matters if the ratios match. So if you're stuck in snow/ice/sand/mud and you have 3.08 front & 4.10 rear, it's fine. But on pavement or rocks, it would put a BAD strain on the axles, u-joints, & t-case. And the engine/trans would behave as if the brakes were on.

Ford put mixed ratios in most '80-96 trucks, but always only 0.01 higher (numerically lower) in front. So my truck was built with 3.07F/3.08R; most fullsize Broncos have 3.54F/3.55R. The reason is that the front wheels pull the truck around turns, rather than acting like rudders.

But all of that only matters when the hubs are locked AND the t-case is in 4.

sprdv1 · Sep 18, 2009

Definitely should match them up....

hillbilly delux · Sep 19, 2009

Thanks all. Just gonna leave the stock gears in for now and beef up my engine a little and maybe a rear spool for posi trac.

Ring and Pinion

hillbilly delux

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thegreatjustino

Red Head Grease Monkey

hillbilly delux

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Broncobowsher

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Steve83

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sprdv1

REBEL

hillbilly delux

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