Up until now, I have had the dealership change the fluid in the differentials - no good place to do it except the driveway and we have a lot of wind blowing dirt and grit around.

Going w/ aftermarket fluids now and waiting for a "calm" day.

I know a lot of folks use amsoil, but that is just not the direction I will go w/ this job.

Rear differential - Mobil 1 synthetic 75W-140 for limited slip differentials. Read a lot of recommendations for it. Visteon 10.5 rear axle. Probably a good time for the 08 differential cover:
8C3Z-4033-A (apprx $50)
Twelve Bolts: stainless hex head 5/16 18, 1 1/4 inch long

Not 100% sure yet on the front differential. Probably will go with Valvoline Durablend semi-synthetic 80W-90 gear oil. Dana 60 Front Axle

I was wondering if anyone would have some reason not to also consider Mobil 1's 75W-90 synthetic gear oil for the front? Anyone used it?

Front Differential:
http://www.guzzle7pt3.com/fdiff.php

Rear Differential:
http://www.guzzle7pt3.com/rdiff.php

Transfer Case:
http://www.guzzle7pt3.com/transfer.php

 

I did mine last Friday, i forgot to order the bolts from ford though just used some bolts from hardware store. I used the valvaline full synthetic in rear have not decided what to put in the front yet though.

 

Hi Mark,

I have Mobil 75W-140 in my rear and 75W-90 in my front. Two changes and 110,000 miles with out any issues. I've never added any LS additive to the rear. Never felt like it needed it.

I didn't have any science behind my decision. It was based on the availability of the product and the seemingly overwhelming number of times it was mentioned in threads on the 6.0, Excursion and SuperDuty forums.

 

Bismic,
Why not build a small tent with some clear plastic
around the truck? That way you only need a calm day.
I was going to do mine here soon and go with Mobil 1 synthetic
on both ends and just get the right weights for each.

Sean