Karb

1996 C4 6 speed. what fluid should i use?

JimLentz

Here is one of many discussions on what to use in a ZF6. I currently use the Amsoil product shown here.

Purple92

I use the Redline Oil MTL in the ZF6 Gearbox.

Many others recommend Castrol 10W-60, Amsoil Synchromax or even Royal Purple.

Cjunkie

Motul 10w60

mtwoolford

I use the stuff they sell over the counter at my local Chevy dealer

dizwiz24

Definitely not bmw motor oil castrol 10w-60

DGXR

Agreed, do not put motor oil in your transmission. Even the original fluid (factory fill) was not simply motor oil -- yes it started with the same base stocks used in Havoline motor oil, but got special treatments for this specific application.

Highly recommend you use a manual transmission fluid (MTF) or "synchromesh" product, there are many available. I run Amsoil MTF, it's great stuff. The GM product would be my 2nd choice, and my 3rd choice would be Pennzoil synchromesh (neither of these are synthetic and I would change them out every 12,000 miles). Have heard good things about the Redline shockproof and Royal Purple products, but haven't used them.

mickey5

I believe the GM synchromesh manual trans fluid is synthetic.

QZRBLU

Here is another vote for the Amsoil Manual Synchromesh Transmission Fluid 5W-30, It replaced my factory fill and it shifts great.

Mick