Outer Limits 4x4 Board

I recently changed the transmission and transfer case oils in my 90 model swb maverick. Now i used castrol multitrax as the oil stated by the manual was not available but they also stated that multitrax is suitable. Multitrax is a GL5 oil. Now I have found out that i should not use GL5 oils in gearboxes as it will stuff up the synchros, and other soft metals in the box. Rather i need a GL4 oil which has half the additives of GL5 oils. Is this true?? If it is what have u guys used and found suitable in these vehicles.

Thanx

why not check out a oil company web site for more imfo you could try www.penrite.com.au i have found them very helpfull or email them at penrite@pentite.com.au i did and got a reply the next day with all the imfo i needed worth a try