Why does Redline say to use GL-5 in the front diff?

Todd Hill wrote:

>  shortlid@PURDUE.EDU writes:
>
> <<  I state for the third time does anyone know of any manufacture
> of GL-4 gear lube I can't find any. >>
>
> Did you call your local VW dealer?  I'm sure they have a can or
> two of their synthetic G50 GL4 75w90 on hand.  If not, or its too
> expensive, then try Redline or an Amsoil dealer.
>
> Run GL4 synthetic in both the transaxle and also in the front diff.
>
> -Todd Hill
>  VolksWerks Transaxles
>  Olympia, WA
>  360-412-0948