4x4 gears
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Junior Member
Joined: Jan 2020
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From: Thorn hill, Tn
4x4 gears
I have a 1989 ford f150 4x4. I have 355 gears. I am wanting to change the gears to 410 so I called a local shop to see if they would do it for me. They told me i had to get a new front differential casing because the factory one will not hold the 410 gear. The said the 410 gear would fit in the rear casing tho. Does anyone know if this is true or are they just trying to get more money out of me.
Member
Joined: Jan 2018
Posts: 11,256
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From: Memphis, TN, Earth, Milky Way
Why do you want to change gears? Going to a lower ratio will NOT make the truck more-capable on-road or off-. A 4.10 pinion gear is physically weaker than a 3.55 - it's more likely to bend or break under heavy load.
The nature of bevel & hypoid gears means that there's a geometry that must change for different ratios. Some differentials are designed to handle a wide range of ratios on the same carrier; others have what's called a "case break", which means the carrier for some ratios is different from carriers for other ratios in that same axle. Google "case break dana 44" to find out if there is one for the '80-96 Dana 44IFS TTB. For comparison, check the '83~04 (current?) Ford 8.8" rear axle.
The gear ratios must be very similar for the axles to work well in 4WD, but Ford rarely matches them. Typically, the front ratio is 0.01 higher (lower number) than the rear ratio. That makes the front tires PULL the truck slightly, which improves steering response off-road. But you shouldn't try to drive far (and ONLY on very low-traction surfaces) with the ratios mismatched (i.e., 3.55 front & 4.10 rear).
My Bronco came with 3.08 rear & 3.07 front, and it's still that way. It's a beast on-road & off-.
The nature of bevel & hypoid gears means that there's a geometry that must change for different ratios. Some differentials are designed to handle a wide range of ratios on the same carrier; others have what's called a "case break", which means the carrier for some ratios is different from carriers for other ratios in that same axle. Google "case break dana 44" to find out if there is one for the '80-96 Dana 44IFS TTB. For comparison, check the '83~04 (current?) Ford 8.8" rear axle.
The gear ratios must be very similar for the axles to work well in 4WD, but Ford rarely matches them. Typically, the front ratio is 0.01 higher (lower number) than the rear ratio. That makes the front tires PULL the truck slightly, which improves steering response off-road. But you shouldn't try to drive far (and ONLY on very low-traction surfaces) with the ratios mismatched (i.e., 3.55 front & 4.10 rear).
My Bronco came with 3.08 rear & 3.07 front, and it's still that way. It's a beast on-road & off-.
Senior Member
Joined: Jun 2015
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From: Oregon
I have a 1989 ford f150 4x4. I have 355 gears. I am wanting to change the gears to 410 so I called a local shop to see if they would do it for me. They told me i had to get a new front differential casing because the factory one will not hold the 410 gear. The said the 410 gear would fit in the rear casing tho. Does anyone know if this is true or are they just trying to get more money out of me.
5 Year Member
Joined: Apr 2017
Posts: 124
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From: SK, Canada
The carrier break is nbd, 100 bucks on rockauto for a 3.92 up carrier. Compared to the cost of having someone rebuild/set up the axle for you, pretty negligible. If it's too much for you though, 3.73's should fit with the stock carrier. Depends on what you're building the truck for, and the parts you're using (tire size, trans, etc.).
If you're set on doing it though, I'd recommend looking into mods the bronco crowd have done; adding a magnetic drain plug, spring loading the right side slip shaft so you don't have to use the c clip, dana 50 slip shaft (if you can find one).
If you're set on doing it though, I'd recommend looking into mods the bronco crowd have done; adding a magnetic drain plug, spring loading the right side slip shaft so you don't have to use the c clip, dana 50 slip shaft (if you can find one).
