Fluid Selection Recommendation/Clarification

[jssgbsn]

I recently picked up an 85 4Runner. I have the FSM.

I have used Royal Purple products in other vehicles for quite awhile with great satisfaction.

I am going to be replacing all fluids and have some questions on some of the oils.  Below are the FSM specs and then what the Royal Purple product 'should/could' be. 

Transmission Fluid      ~~ SAE 75W-90, API GL-4 or GL-5     ~~ Royal Purple Max Gear or SynchroMax (SAE 75w-90)
                     
Transfer Oil                 ~~ SAE 75W-90, API GL-4 or GL-5     ~~ Royal Purple Max Gear or SynchroMax (SAE 75w-90)
                     
Differential Oil              ~~ SAE 90 API GL-5 Hypoid Gear Oil  ~~ Royal Purple Max Gear SAE 90
                     
Steering Gear Box Oil ~~    SAE 90, API GL-4                          ~~ Unknown Equivalent ()


Their Synerlac Additive, like other brands, says their GL-5 is 'backward compatible' to GL-4 to protect yellow metals)      

Here are my questions.

1.) Max Gear or SynchroMax for the Trannmission? (W56 Manual 5Speed)
2.) Max Gear or SynchroMax for the Transfer Cases? (Dual Marlin)
3a.) Max Gear or SunchroMax for the Differentials?  (Rear Differential is a Detroit Locker)
3b.) Are their any other friction additives that should be used in a Detroit Locker?
3c.) Should I be using a seperate oil for the Front and Rear Differentials or use the same?
4a.) Max Gear or SynchroMax for the Steering Gear Box?
4b.) Since Royal Purple does not a GL-4 specific application, any recommendations?


I tried finding these answers on 'bob_is_the_oil_guy' and other reputable sites/forums but i get conflicting info. 

I typically have always used OE, OEM, OES parts but aftermarket fluids (except certain coolants).

Since this is the ultimate stop for Toyota guys I figured somebody here would know.

Thanks in advance for any insight. 

[emsvitil]

Not really an overall answer........

If you have power steering, you'll be using ATF for it.

Otherwise for the steering gear, I'd use whatever I had left over from the tranny/transfer first, differentials second.


A locker doesn't need any additives.   Friction type limited slips need the additives  (trutrac limited slip types don't need additives)

Some gear oils already have the additive in them.

[Rocksurfer]

I understand the desire to have a "designer label" for the talking points in the garage but a few things to consider here for you, if you are doing a rebuild then breaking in the engine with a type of oil is best and staying with that type (synthetic/standard) your seals have been conditioned for that type and changing could lead to leakage. Also even though you show the proper GL numbers a synthetic oil will will still make the gears and syncros slide easier and may cause grinding when you pass through the syncros to fast.