My truck is coming up on 6 years old and we're about to go on a long road trip, so I thought I'd swap out the rear diff fluid. It only has 36,000 miles on it. Maybe 3,000 of that was hauling our 6,500lb travel trailer, which we got rid of 2 years ago. I knew this was pretty early, but I figured, what the hell. I was shocked at how dirty and milky the fluid was! No metal particles or chips, so that's good. I've got 2 old Jeeps with big lifts and wheels, so I do a lot of diffs. I think my truck was the dirtiest I've seen. Glad I changed it.

 

There has been several posts about early water intrusion and such on these trucks. One of the reasons it's recommended to change it far earlier than the manual shows.

 

FordTechMakuloco says 30,000-60,000 miles, so I guess I'm in the target area according to him. By the way, I used Amsoil SEVERE GEAR 75W-90 fluid. Love those bags it comes in!

 

Agreed, 30-60k is a good range depending on usage. Absolutely those bags make the job so much easier! Thank you, I appreciate the business!

 

I'll be doing mine soon too and was also going to use the bags. I have just over 50k miles and I bet it hasn't been done.

Did you change your bolts too or reuse them?

 

I re-used the bolts. There was a gasket in mine, a metal gasket with a rubber seal. Also looked like they used some sort of gasket cement at the factory, so that had to be cleaned off. Both the cover and the pumpkin had quite a bit of rust on the sealing surfaces. I had to sand it all down to bare metal. I used Permatex "The Right Stuff" for sealant when reassembling. Good instructional video here: .

 

I bought the gasket from Mag Hitec for the Super 8.8, which I have. I know I have to scrape off the RTV sealant from both parts. There might be rust too.

 

PM me if I can help you out with the fluids.

 

Well I suppose I should do this since I'm at 90k

 

I do mine every 50k in every RWD vehicle that I've ever owned. It's cheap and easy maintenance.