View Full Version : Posi unit and which fluid to use

02-13-2002, 06:42 PM
I just had a shop by me put in a new Auburn Pro posi unit and 4.11 gears I know he told me he put synthnic (spelling) fluid in there and no addive. IS this correct ? or should I drain the oil and put the reg 80/90 with the GM additive in there??

Please let me know before I hurt this unit


02-13-2002, 10:42 PM
I have always been a firm believer in synthetics but have heard from a few sources not to use it in a hi performance 12 bolt application. <img src="images/icons/confused.gif" border="0"> More importantly I think is the GM additive, I once left it out of the rear on my '87 IROC after a fluid change and it was making some serious noises. I had to drain it and do it over again using the additive but that was just a stock rear.

Round Rock TA
02-13-2002, 11:34 PM
Use the search function. I did and guess what I found. 100 people saying 4 different things. It is amazing. Do a search and you will see. Synthetics are only the half of it. What weight? What additive? Do a search and you will see.
I went with a blend and used the GM additive. I went with the heavy weight since my pinion seal is not the best.