moonlightgambler

Hello, i am a young ford enthusiast who is currently rebuilding a 1990 ford f150 with 35 inch tires, that i recently purchased. my latest problem is i found my truck has 3.08 gears in the front and rear. Since my tires are so big and i plan on going bigger i need to know what i have to do/buy to put in 4.88 gears in the front and rear. i am currently getting 5mpg with a streight 6, so hopefully bigger gears will help my engine run better.

construction ford

The gears will most likely help but if you do a lot of highway driving the 4.88 might be a little bit low maybe go with 4.56. The reason I say that is because the 300 straight 6 has all of its power down low and you dont want to have to run it at high rpm anymore than necessary.

Manuellabour247

Look in the gear thread for the calculator. Can't remember off of the top of my head who posted it though. 4.56 might be just about right for slightly better than stock with 35's. But like said above, the 300 is a lugger motor. What were your stock tires for that truck? 235/75R15's?

superduty

Iirc your 8.8 won't support a 4.88 ring gear. The teeth would be too thin. Someone chime in it that's false. 4.56 is about it. Gears would definitely help a lot tho.

Chris_1

iTrader: (1)

I think you also have to get a new carrier. From what I've been led to understand .... the 3;08 carrier will take 3;56 and 3;73. To go 4;56 or 4;88 I think you have to go to a different carrier.

superduty

Yeah. Idk about the carrier. Now that I think about it. 4.88 might be the limit but was not advised because of reliability issues for the teeth being so thin. If you go big enough to need more than a 4.56 you should prolly upgrade to bigger axles. (1 ton) IMO.

Brandon587

If you plan on going much biggethan 35s I would advise going with at least 3/4 running gear. Especially if you are going to go off roading in it. Not that the 8.8 and Dana 44 wouldn't handle it, but you are stressing it too much and if you aren't easy off road something will eventually go, like say, an axle.

Manuellabour247

Something I didn't see asked. Do you have an automatic or standard? It will make a difference in the feel when driving it around. Especially if you have a 5-spd.

sdmartin65

I'd go 4.10, they can be had from Ford Racing and can be installed cost effectively. The front requires some more work and parts above 4.10. FR gears are the quietest on the market not sure if that will matter with 35's. Some gear brands can be very noisy even when properly installed.

Brandon587

the front requires a carrier swap even with 4.10s, if that's what your referring to as more parts.