I got curious about GL-4 and GL-5 since O'Reilly didn't carry GL-4 except for 140 weight, and I ran across this paper. It tells exactly why we don't want GL-5 in our xfer boxes. We might want this on the FAQ page.

The difference between gl4 and gl5 gear oils

1995 SR, dark blue, cloth seats, flare and cladding delete, upcoming sunroof delete,10 Guage custom skid plates, ham radio