Help: ZF6 fluid help

[chevytuf01]

Need to change the fluid in my ZF6 speed in my tow rig ... what kinda fluid should I put back in it ... I know GM part #12378515 is synthetic transmission fluid is what it calls for but what can I use in place of it

 

[clrussell]

I used dex 6 in mine.. Did some googling and it that's what everyone else was doing. So far so good after 500 miles.. No weird noises, hope jt was right

 

[chevytuf01]

Cool thanks ... that's what I was thinking I thought about throng a bottle of that thick Lucas Trans fluid in there as well