jmburton1993

I have a 98 f150 2wd v6 5 spd lifted on 33's with stock gears which i think are 3.10's. does anyone know how hard it would be to yank a rear end from a junkyard truck and swap it in for lower gears, preferably 3.73's, or should i just bite the bullet and pay to have the gears swapped

jferg92

Several people on here have searched for 9.75's with the 3.73's and have come up short. Can't hurt to look though. Well I'm assuming you were trying to swap your 8.8 for the 9.75?

jmburton1993

I'd like to go 9.75 but if not I'll be fine with the original just don't wanna bite off more than I can chew on the swap

akdoggie

Look at the drivers door post and see what number or letter number you have by the axle code. If it is 18 it is 308's, 19 is 355's and if you have letters H9 you have LS 355 and if you have B6, you will have 373 with LS.

jmburton1993

It's 18, I have to do something my mpg is terrible, would a swap take more than a day to complete?

jcavers

Shouldn't take more than a few hours. Just do yourself the favor and soak all your bolts with a penetrator the day before, oh and fill the diff before you put it under the truck

akdoggie

If you have a complete differential out of a similar year (97-99) you shouldn't have many problems. You have drums, so you are good thru 99 in most cases without changing probably anything. There were a few 2000's with drums also, but remember if you switch to those that you will now have 14mm studs on the rear axles and your lug nuts won't fit. We have 12mm studs until late 99 (?). If you had the lug nuts handy, you'd be able to switch your diff in one day, item to item.


If you decide on going to the disc set up, you have the different master cylinder (some will say don't change it but with brakes, you shouldn't take a chance). The parts books definitely show different m/cyls for the disc vs drums. The same goes with the proportioning valves. Changing to the later rear ends, you'll also have emergency brake cables to change because of the disc set up. There are a couple more items that might mess with you if you go with the disc set up. You might not get that done in one day, but it is the perferrable change out if you can find an appropriate match. It's one I have definitely planned for a future modification for my truck.

jmburton1993

Thanks I think I'm just going to go with the 8.8 for now found local pull a part has 3 trucks fitting the year range which I could use just have to keep my fingers crossed no one has gotten the parts I need yet and that they have the gears I want lol

Plague

Just my opinion but I'd just do a gear swap and keep the original 8.8 rear end. I wouldn't trust a junk yard rear end unless it were opened up, cleaned, the bearings replaced, and the ring and pinion inspected.

You never know what exactly your getting with parts from a junk yard. The rear you may find could have been ragged on and mistreated or you could find a diamond in the rough. Plus you'd probably have to totally redo the rear brakes and maybe the e-brake system. I think you'd be smart to just keep your 8.8.

Danruff93

If you do get a junkyard one you can keep the original for a spare if it goes