89 f250hd with limited slip differential
it needs special differential fluid

How does it get changed?

 

Before you start you need to get a new differential cover gasket, blue RTV if you fancy (i like to add a thin beed to both mating surfaces), LS additve from ford and a couple quarts of the treccomended gear oil for your truck (should be listen in the manual).

To Drain:
Remove the front cover bolts and cover, allow the gear oil to drain into a pan, when it stops wipe off any excess oil in the housing and on the gasket surface, clean the gasket surface of gasket material and any RTV from both the axle and the differential cover.

Assembly:
Apply a thin bead of RTV to the differential, make sure the bead goes around both sides of the bolt holes in the carrier and cover, allow to sit for a minute and then apply the gasket to eaither the axle or the cover and bolt the cover back to the axle allow RTV to dry for the reccomended time.

Fill:
Find the fill plug, should look allmost like a really big setscrew only that you don't use an allen key to remove it but the part of a socket wrench that holds the socket. Remove the plug, and pour in the LS fluid. After that start filling it up slowly with gear oil allowing the oil to flow into the axle tubes. Kepp adding oill untill it starts to pour out of the fill hole and quickly put the plug in and tighten it up and your all set to go.

 

I would add, that it may be easier to add the oil if you have one of those hand pump thingies that attach to the bottle of lube. Mix in the diff additive with the lube.

Jim Henderson