I went with what the book said (still have the pics on my phone)
Then bought like fluids from Advanced Auto parts (used to be Carquest) online to take advantage of the 20% off coupon that pops up when reviewing their items. I picked them up on the way home from work and they had it all ready for me when I got there.
The rear end fluid I chose stated it was for limited slip differentials, no need for additive.
I used the Carquest branded fluid in the front end and Either Valvoline or Mobil one in Rear end. (Don't remember)
Don't forget the transfer case, it's the easiest of the three to do.
I used the Lucas oil full synthetic $7 a quart at rural king, maybe $50 a gallon at O'Riellys iirc. Mobil 1 and valvoline make good stuff too.
75w 140 for single axel and 450/550, 350 dually is supposed to be 75w 90. 80W90 for the front, the front open. Honestly I used the Lucas 75w 140 for both front and rear.
The biggest thing is to use a full synthetic, technically the LSD friction modifier reduces the effectiveness of the limited slip. Essentially making the clutches slip so they don't bind up in a corner. Best to refill with full synthetic fluid without adding the additive, and test drive. If you get chatter then pull some fluid out and put the additive in.
A lot of the conventional rear end fluids, like the carquest, will say "for limited slip" on the bottle. Read the fine print and it's for top off only. If you do run conventional it needs changed every 3k, the only reason I can see to do this is if your running through high water frequently, impending rebuild, or topping off because of a leak. Change it out at the time of repair.
LSD is not necessarily standard, could be open. You would know if you had the e locker. Check the axel code on the door sticker and cross reference on the Google or call Ford to see your gear ratio and type.
I looked up a vin decoder and i could only find my gear ratio, nothing about LS or not. Since diff fluid services are rare I was going to go with Royal Purple. Theres already has a premix for LS. Would that be bad if it's not an LS diff? I had already planned on synthetic for both so the service manual wasnt any help
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