API service Gl-4 Gl-5?
 

my 91 service manual says to us Gl-4 Gl-5 manual transmission oil. So why not Dexron-II or M-II. im going to change my trans fluid and need some info on what i should use in it. And is Castrol GTX a good motor oil for my car?

Dexron II is a auto tranny oil

are you replacing the gear oil on a manual tranny???

yeah well i took off my drive shaft and this dark black oil came out and it wasnt red like other trans oil and it smelled like a gear oil.....so is that what goes in the trans gear oil???
if so how much and what brand.....im just going to drain it from the plug and put new oil new while im down there.

Gear oil (90W or 85W90) goes into a manual tranny, GL-5 if you can find it.

I recommend Redline MT-90 in most FC's, but if you are racing heavy duty, then Redline Super Light Weight is also a good choice, as it is a 85W90 and would rate as a GL-5 if Redline rated it.

If you can't find Redline, then Castrol is a good choice. Avoid GL-4 oils however if you drive hard as they tend to break down at higher temps (anything above 220-240F) and then can damage the syncros.

GL-5 is just the specification for purity and load characteristics. Gear Lube-5

I personally use Castrol GTX without trouble, to answer the motor oil question.

cool....thanks guys