I have I 1995 7.3 turbo it has a 5.13 gear in the axial with a 4speed with over drive my question is will a 1999-2001 f-450 or e-450 work under it or will it be better to do a new ring and Pinyan Pinyan gear and I pull a lot with it but at55-60 its 2500-2800 rpm I don't like that

 

It is just a Dana 80 rear, so its not to hard to find a used 4.10 r&p. A r&p from a dodge should work. There should be a bunch of srw 80s around. The newer SD 450 axle should work, but it will be a big 8 lug. And still have 488s or 456s or something still low.

 

welcome to FTE.
the thing to remember with the F-SuperDuty is that you are trading speed for weight capacity.
if you tow heavy weights you need the gears and have to forfeit the speed.
if you put a 4.10 gearset in the rear, you will be able to go faster, but will no longer be able to pull the heavy loads reliably, and may see even lower fuel mileage because the engine will work harder to get the load moving than it would with the 5.13 gears.

 

5.13s do seem awfully low for a 7.3, don't they? I always thought the 460 F-SDs had the 5.13s and the 7.3 F-SDs had the 4.63s, I could be wrong. You could still tow a fair amount w 4.10s, maybe 4.30s if you can find them. I was looking to go the 4.30 route with my truck.

 

the old idi trucks had 3 gear options if i remember correctly, 5.13, 4.63, and then there was the very rare 3.73 gears.
i have only heard of 373 gears though, never see one with them in it.
aftermarket you should be able to buy 4.10 gears though.

 

You mentioned that you tow a lot. I guess it comes down to, how much weight are you towing?