Thread: Gear ratio

So I just found out that my rear end is going out in my 1984 f150 with a 300 i6 4.9L and I'm going to change out the whole rear end axle and everything and I was wondering what the highest gear ratio I could put in it. For good gas mileage purposes only, well that and I'm tired of going 5 mph in first gear.

You can go as high as you want that'll fit in the differential housing. For good mileage however, I would stay anywhere from 3.15-3.31, 3.55 at the most. What size is the rear end?

Honestly I don't know I think somewhere around 4:10

I've always thought 3:73's were a good mpg/acceleration trade off in my opinion .I don't think you have 4:10's, if its stock at least

I don't think it's stock. And it's pretty low gears

I meant size of the rear end, sorry lol. As in my '05 has 3.55's but the size of the rear end is 8.8"

Originally Posted by judaspriest75

I don't think it's stock. And it's pretty low gears

Oh, well if it is 4:10's, a swap to 3:73s might be what your looking for. Go too high and you'll hate it cuz you'll have like zero acceleration lol

Would 3:50, 3:00, or 2:75 word and if so, what would be the highest ratio?

Are you replacing the whole axle or just the gears?

I might just go ahead and replace the whole axle maybe but it's whatever I would be able to do in the next 5 months Till I enlist in the army