What gear oil can I use in the Tranny and T-case? The owners manual says to use Manual Transmission Fluid HQ Multi 75W-85 or equivalent for the tranny and API GL-4, SAE 75W-85 or 75W-90 or ATF for the T-case.

The differentials use GL-5, SAE 80W-90 for LSD.

I'm having trouble finding GL-4 gear fluids. So far the only one is Pensoil Syncromesh Manual Transmission Fluid (at $14/quart). Can I use Castrol Syntec 75W-90 even though it's a GL-5? Will it cause any problems? Where can I find the proper fluids? I've tried Wal-Mart and Lordco Auto (like a Pepboys).

Oh, and finally, which oil companies make these certain fluids? I would like to keep the same brand for everything, ie Castrol.

Thank you in advance.