I just purchased a 1992 F Heavy Duty. I wanna change the rear end ratio because it came with 5.13 gears. I will do a lot of highway driving and want to swap these out for something a little more highway friendly. I found a 1992 F-350 rear axle with 4.10's. I was wondering if anyone knows can I just swap out the rear axles between these models? Thanks for any help.

 

Yes and no.

Your F-superduty has a cab-n-chassis rear axle(aprox 40" center of spring pad to center of spring pad), So that means you will need to find an F350 that is a cab-n-chassis. And you will also need a dual wheel F350 cab-n-chassis. A pickup(with a bed, dually or single wheel) has a 44.5" center of spring pad to center of spring pad

The next obstacle is the brakes. The F-superduty has dis brakes while the F350 has a drum brake.

the next thing is you will be reducing the gvw of the truck by putting a F350(11k gvw)axle in place of the F-superduuty(15k gvw) axle.

then there is the whole 10 lug vs 8 lug deal. The F-superduty has 10 lug wheels and the F350 has 8 lug wheels, so you would need (4) 8 lug wheels for the rear axle

 

Thanks Brad,

So basically it sounds like it'll be a lot easier to just change out the ring and pinion. From my understanding the Super Duty has the Dana 80 rear end. Do you know if it's a 35 or 37 spline? I'm not home yet to actually take anything apart and look.

 

I do not know. I only ever had one of those trucks