I am going to change all the fluids in my truck this weekend, been sitting for 4 years+.

After a few hours of searching forums I am no further ahead, maybe a little confused.

Truck is 1985 F350 4X4 4SPD 460.

I am assuming I should use 75W140 synthetic in front rear diff? The Royal Purple I was looking at already had the additive in it.

What should I use in the tranny/transfer case?

 

Axles front and rear 80w90 with an additive if limited slip diff. However I would think the Royal Purple would be good.
Transmission 75w90 gear oil.
Transfer case automatic trans fluid.
That`s what my book says.

 

I was going to do a fresh post until I came across this thread, so I will post it here. I am replacing the rear access cover due to it having rusted through. The axle is an 18 [3.05] and the oil I have 80w-90 GL-5 rated. Will this work or do I need a different lubricant?

 

Oil & Lubrication - Ford Truck Enthusiasts Forums Might be better posting on this page.
As I understand it GL5 spec. lube is for specific transmissions and transaxles. I don`t know if it would suit your application or not.

 

Thanks for the quick reply, am off to search it.