'Traditional' old fashioned Transfer Case Lubricant? GL4 or GL5?

[pgtr]

'Traditional' old fashioned Transfer Case Lubricant? GL4 or GL5?

This came up in my mind in another thread and it got me thinking... (always a dangerous thing!)

This is sort of an 'old school' theoretical question...

I'm not talking about modern transfer cases, AWD, anything 'automatic' but the bulky, discrete units you might find in an old Jeep CJ or Toyota or something. The kind that you'd have to bring the vehicle to a halt when entering or leaving the trail and then take the separate transfer case stick and put it in either 2H, N, 4H or 4L. (you probably have locking hubs you had to get out and switch - am I dating myself!?).

These would have typically spec'd an SAE90 or SAE80 (cold) GL-something or other back in the day. They would not share lubricant from the 4 speed. Just imagine a basic old fashioned traditional transfer case from the past.

Nor am I talking about modern synthetics or GL4/5 combos etc. Just a simple generic question about the applicability GL4 vs GL5 spec lubricants. If you like, presume an SAE90 or SAE80 or an 80W90 or 75W90 as you prefer in both cases. Not interested in weights or synthetics or anything like that - just the API spec.

Would a GL4 or a GL5 be better or does it matter?

On one hand there typically are no synchros so that should not be an issue with either oil right? (Heck the old units I'm familiar w/ back in the 60s or 70s were hard enough to shift standing still!)

On the other hand aren't we talking about straight cross cut or spur gears? - no hypoid of worm gears? If so are the increased EP additives of a GL5 unneeded? Or can you ever have too much?

So what do ya think?
A) GL4 or
B) GL5 or
C) either
...and why?

I've really got to shrug on this one and figure it doesn't make that much difference. GL5 of course wins hands down on convenience and availability.

thanks,

PS: I guess the ultimate wishy-washy answer would be a GL4/5 'combo' eh?

 

[unDummy]

I don't think that it will make a difference in the transfer case. Use whatever lube you want.

Manual hubs rule! Too bad everyone is lazy(or too incompetent) and need auto-lockers!

Noone has studied whether GL5 has more EP/AW than GL4. Also, there are different types of EP/AW that can be used. I am also guessing that different base oils can have different PPM of different types of EP/AW in order to meet the GL5 spec. From what I've read, I'm assuming that the GL5 spec is a WEAR test and not a "quantity of EP/AW" PPM analysis.
It is different than motor oil and AW which is held at ~.1%(?) to make API and treehuggers happy

 

[BOBISTHEOILGUY]

for the fun of it, I took two oils, one gl-4 and one gl-5. Both made by the same company and had Virgin Oil analysis done on them. I then posted them on here so you can see the basic difference between the gl-4 and gl-5 oils. Here's the samples outcome.

code:

---

ADDITIVES GL-4 GL-5

MO 1 0

PH 440 1103

ZINC 9 12

MAG 0 0

CAL 23 13

SUL 0 5

---

Notice that the real difference between the two is the PH. Just what you'd expect to see.

Go here to see the whole topic on these differences.

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=11;t=000022