I dunno about your truck, but the owners manual for the Range Rover has all the specs for lube and fluids.
I shop for goo at the Tractor Supply, Atlantic Tractor, Wal mart and sometimes Costco.
I generally use Rotella in the engine and el cheapo for 90 wt and dexron 3. I do have a 5 gallon bucket of John Deere gear oil that was a good deal. Coolant is Dex cool. Brake fluid always Girling.
Get a bottle pump for your gear oil and change the diffs at least once a year.
1966 109 5 door wagon 300Tdi "spermaceti fueled"
1994 RRC LeWiB "ruining the air behind me"
All my troubles are Rover