Im looking for the next project to do on my truck, and want to intall a posi. The problem is i dont know a lot about the rear end and my question is how do i choose which posi will fit my truck? also what are some good posi manufacuturers?

 

First things first.
Crawl under your truck and look at the axle tag. It will give you info that looks something like this 975 73 LS(this may or may not be there).
The 975 means that you have 9.75" rear end.
The 73 means that you are running with 3.73's for gears.
The LS which may or may not be there. IF it is then you have the limited slip option already.
Post that up and then we can help you out more.

 

if you have a 5.4 then you have the 9.75

if you have a 4.2 or 4.6 you have the 8.8

Theres a sticker on the door jam. read that and tell me what it says under "axle" then ill tell you what you have

 

If you don't have one, Detroit TruTrac, Eaton Posi, and Auburn HP all make excellent LS/ Positraction units. If you keep you truck on the pavement and simply want LS, but not a performance unit, you can get the Ford LS unit for about 250 from Summit. All of the other units will run $400-$600.

 

I have a 4.2L, Im at work so ill check the axel on my lunch break, but what if i decide to regear my truck later on would i have to get a new posi?

 

id do it all at once... you will save money!

you have he 8.8 axle. ill tell you the gears when you give me the code!

 

ya do them both at the same time it will save you extra labor they will already have it torn apart so may as well just do it while your there.

 

the number under axle was 19, is this the code? and what are some good web pages to get more info on regearing my truck.

 

you have the 3:55 non-limited-slip.

what are your plans with the truck?

 

My plans are to use it for offroading, because i live is So Cal. i use it now for dirt, a little mud and sand whenever i take trips. i curently have a 3.5" fabtech spindle lift with 33" tires. I plan to make it a prerunner and drop a bigger engine in it but thats far into the future, and as for regearing it i will probably hold off on that too as it is a bit expensive. For now im just looking for a posi so i can have a bit more fun and not get stuck.

 

two links that have ton of info on re-gearing are:

1: https://www.f150online.com/forums/ot...p-rev-1-a.html

2: https://www.f150online.com/forums/ot...supercrew.html

 

Ive been doing a lot of research and will probably go with the eaton posi, but which one fits my truck the 28 Spline Axle or the 31?