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Quick Facts

  • 2WD Trucks have 1 differential - rear only
  • 4WD Trucks have 2 differentials - front and rear
  • Differentials on F150s come in 2 sizes: 8.8" and 9.75"
  • 8.8" Differentials have 10 bolts on the cover
  • 9.75" Differentials have 12 bolts on the cover
  • On a 4WD truck, you can have different size front and rear differentials
  • You cannot mix and match front and rear differential gears
  • On a 4WD truck, your front and rear differential gears must match

Driveline Basics

When it comes to changing your truck's gears, you should understand a few basics about its driveline before choosing your gears.

  • If you have a 2WD truck, you have only one rear differential, or just "rear" for short.
  • If you have a 4WD truck, you have two differentials - a front and a rear.

The second step, and possibly the most important, step in changing the gears in your differential(s) is identifying what size rear (and if applicable, front) you have in your truck. Ford used two different axles in their F150s from 1997 on, and they are vastly different in size.

Thankfully, this difference makes identifying which one(s) you have as simple as looking at them. The two possible differentials your truck could have are the 8.8" or the 9.75" differential.

Please note: you should always inspect your truck to determine which differential/rear you have before buying gears. Any fitment specifications are general rules only, and can vary.

We strongly suggest you inspect your truck before choosing your new gears.

Also, just because you have a 9.75" rear doesn't mean you have a 9.75" front - in other words, you should inspect both differentials to determine which size you have in each location since they can differ.

Identifying Ford 8.8" Differentials

The first, and most common axle on most Ford vehicles, is the Ford 8.8. This differential has been around since the early 80s in the F series trucks, and is most commonly found on the 97-06 4.2l and 4.6l model F150s. This axle can be identified by the 10 bolts on the differential cover.

Important Note: all front differentials from 97+ in F150s are IFS (independent front suspension) versions of the 8.8 rear. The front differential parts can NOT be swapped with rear 8.8 differential parts due to the differences between the IFS front axle and the solid rear axle.

For example, if you have a 4WD truck that has an 8.8" front and rear, you can't buy a rear 8.8" gear and put it in the front - they're not compatible. You have to buy front gears for the front, and rear gears for the rear. (Same applies for a 2WD truck, you can't buy front gears and try to put them in the rear).

Once again, make sure to inspect the other differential - they do not have to match in size.

Identifying Ford 9.75" Differentials

The axle that is most commonly found on 97+ F150s with the 5.4l engine is the Ford 9.75 rear. This axle became the only rear found in the F150s in 2007. The 9.75 rear axle can also be identified by counting the bolts on the differential cover - in this case, 12 bolts.

And if you have a 4WD truck don't forget to make sure to check your other differential to see what size it is too, since it is not necessarily a 9.75".

So I've Identified My Differential, Now What?

You know which front and rear differential(s) you have, and you've chosen a gear ratio that's right for your needs.

So, now what?

If you have a 2WD truck, you need to purchase the rear gears you want in the ratio you've chosen and any other important items for your installation. For example, a bearing kit is good insurance on the life of your new gears and differential, and a 8.8" rebuild kit is a great upgrade to your existing differential and a great compliment to that new ratio for low-end bite.

If your truck has 4WD, however, you'll need to change both the front and rear gear ratios to match - in other words, if you want to go to 4.30 gears in the rear, you'll need 4.30 gears for the front as well. Make sure when purchasing your gears for your 4WD truck that you purchase front gears for the front differential, and rears for the rear in the correct size and matching ratios. Also, just like with the 2WD trucks, it's cheap insurance if you buy a bearing kit at the same time for both differentials.

Now that you know what you need, start browsing our gear selection for great parts from names like Motive and Ford Racing and you're on your way to more torque and the stump pulling, tire smoking power you want!