Hi guys,

Going to change my transmission fluid today but can't find a definitive answer on what spec GL-4 fluid to use (75w-90 for example).

Does anyone have a definitive answer?

 

-chase

A bunch of us run this 75/90...

https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil

ok, I'll grab that.  2 quarts should fill a '78, right?

5 hours ago, chaseincats said:

ok, I'll grab that.  2 quarts should fill a '78, right?

Yes,  if it is a 4 speed.   A 5 speed takes slightly more.

The Redline gear oil is very good,  I have used it,  however many of us have switched to AC Delco Friction Modified with great success.  Something to consider ...

15 minutes ago, S30Driver said:

Yes,  if it is a 4 speed.   A 5 speed takes slightly more.

Funny, I never really realized this.  The 1978 FSM has both, for reference.  I wonder where the extra capacity is.  Bigger rear case?  Or did they just move the fill hole up to keep the new gears covered.

Edited July 7, 20206 yr by Zed Head

59 minutes ago, Zed Head said:

Funny, I never really realized this.  The 1978 FSM has both, for reference.  I wonder where the extra capacity is.  Bigger rear case?  Or did they just move the fill hole up to keep the new gears covered.

wow ya that is interesting

weird