how do i know what my spline count is in my rearend..... i am looking to get a rear oem posi locker for my truck off ebay and idk if it will fit?

any help will be appreciated

 

some more info on your rear end and truck would help

 

you should have a 28 spline 8.8 since you have an 04 xlt

 

28 unless you have a FX4.

however if you had a FX4 then you wouldnt need a LS off ebay...

 

its an 04 xlt with an open diff

 

all axles (7.5 and 8.8) had 28 spline axles except for the 2002 FX4 Off-Road and the 2003+ FX4 Level II packages. the 02 FX4 and the 03+ Level II had 31 spline rear axles and all of them came with a torsen limited slip differential. So you've got a 28 spline.

 

What do the splines do/determine.

 

the shaft has the splines at the end that the ends slide into the carrier unit which has the gears..inside the carrier accepts the splines which makes a gear and turns the unit..

the driveshaft turns the pinion gear..turning the pinion gear..turning the shafts..turning your tires..

the more splines the stronger

 

Not really just "the more splines the stronger". Basically, since the splines are cut to a pretty standard size, more splines means that you have a bigger diameter axle.

It's the axle diameter increase that gives you the strength, but the spline count is just used to identify the difference between the two size axles.

31 spline 8.8 axle shafts are 30 percent stronger than 28 spline axle shafts.

 

Mustangs run the 28 spline axles and in the car they are good to almost 400hp before you need to upgrade. So a street ranger should be good with a 28. Now laying power down on rocks/mud etc. the larger 31 spline may last better in that arena.

 

The 28 spline 8.8 is pretty durable overall. I agree you only need the 31 spline in special circumstances. I saw someone break a 28 spline in a Ranger though just by spinning them down through the snow and hitting solid ground. Candy-caned it. it was a stock truck overall. I think it had 31's on it and that was about it for mods.

 

and a locker??

 

And 32's?.......

 

Ah, 32's, lol. My recall is faulty...(so what's new? )