Redline Gear Oil - Help I'm Confused

["Mark Pollan" <Mark.Pollan@MCI.Com>]

Please help, I am totally confused by all the various Redline products.
All I want to do is change the oil in my differential and transmission
(5spd).  The car is an '86 5KCSTQ.

>From an unnamed vendor (don't want to give him a bum rap because of
my ignorance I first received Manual Transmission-Manual Transaxle
Lubricant of the 75W/80W GL-4 variety.  Placed a call saying it was
the wrong stuff and specified 75W90 gear oil.  Promptly received High
Performance Gear Oil of the 75W90 GL-5 variety.

Bentley says 75W90 GL-4.  How do I refer to the right stuff or am I
missing something?  The trans and diff use the same oil right?

Your help is greatly appreciated.  I don't want to make an oh so costly
mistake with the gearbox/diff.

Mark Pollan, '86 5KCSTQ 228K Miles which I want slippery but not too
slippery.