I have always wondered if there really is an advantage to using synthetics in a auto transmission or posi rear-end. I have it in the diff now, and was going to switch the transmisson than thought. Hey, why would i want to put something that slippery in a unit that relies on friction to do its job. Am i the only one that thinks this, or am i on to something here. Thanks Prorac1

 

You got it right. You do not want to use synthetic oil in your transmission. Transmissions need a lil friction to work properly. Synthetics are was too slippery for them. As for the diff. synthetics will work but regular oil for it is just fine.

 

If you have an aburn posi unit, which I think is factory for our years, they recommend regular gear oil.