F250 2wd gears
 

Hey folks, I have a 75 CC, 2wd, 390, manual 4speed w/ granny and 4.10 rear end gears. My tires are 29.5 tall so it don't take long till the RPMs are making me want to shift to fifth gear which I don't have. I found a posi with 3.5 something rear end gears. Would that be to much of a jump. It will be towing a 22ft camp trailer during the summer months.

I highly doubt that's too far of a jump with a 390 4 speed.. I'm sure there's someone here who can answer out of experience ..

Good luck

Thanks Fred, I'm hoping it will work

Let this table be your guide?

https://i200.photobucket.com/albums/...eGearsize2.jpg

Thanks Silver, I could always get shorter tires. Cheaper to get smaller tires than taller ones. If it was a 4x4 I would go bigger

I think you will be fine with the torque an FE makes, I ran 4:10 gears and 33's behind one with a 4 speed and still needed more gear. Swapped to 3:55 and loved it with a 29 inch tire.

You got that bass ackwards, A shorter tire will bring your RPM's up, a taller tire will lower RPM's

Taller tires with the 4.10 and shorter with the 3.55. The rpms are to high at 55 with the 4.10s & 29 inch tires

For towing kinda heavy, I'd personally go with a bit taller tire and keep the 4.10's. With 31" or 32" tires it should handle speeds up to 70 or so and still tow well. Yes it the engine will spin a bit but can take it fine. My 78/400/4.10 does fine at 70 with 31" tires. I'm running 245/75/16 10 PR on steel wheels. Pretty close to 9.50x16.5" which was on the truck before the switch to 16's.

2 wd makes it easy to swap rears only if desired.

looking for a little better gas mileage also. Gearing is cheaper then tires