Hey all

I'm getting ready to have some fun with the rear differential. I'm just going to change the oil. But this will be my first diff.

89 F350 7.5 460 ZF5 manual. According to the door sticker (axle code is 39) I have a Ford 10.25 3.55 rated for 6250 lbs. That said, lots of things on the truck have been replaced so I'd like to make sure what I've got first. The wheels are not Ford originals so I thought I'd check on the axle.

Here's a shot to help identify it. I can see 5T8CA and I think the rest is OSWDF


1989 Ford F350 460 5 manual

As you can see in the next photo, I have an old leak at the bottom of the cover in the rear. The front is caked with oily grit too, and the knuckle connecting to the driveshaft is covered in oil & grime, and apparently has been splattering oil on the underneath of the bed for many years. So I am definitely expecting the old seal to be shot and the oil inside to desperately need to be changed. I have no idea what else I might find, or what how much of an issue any of this might turn into. Before I change it, I wanted to be sure I had the right differential so I could get the proper oil for starters.


1989 Ford F350 Rear Axle

 

It's a sterling 10.25 full float. Exactly what should be there.

 

@bbf385
Much appreciated!

I'm very impressed with the Lucas oil in my transmission now, so I'm going to see if I can find the Lucas 85W-140. I understand that's the high (climate) temperature version of 85W-90. Since we're in Texas I thought that would be the way to go.

 

Anxious to see how it works for you.