dream69

I've got a 1996 Z28. Is there a spacifice fluid to the fluid in the stock rear. I was told that there was a synthetic additive that must be replaced or with normal gear oil the rear will begin to howl soon after. Is this true and is it the posi trac system that it damages?

jsteele90

iTrader: (13)

gm posi additive and valvoline synthetic 75w90 gear oil is what i use

dream69

where do you get the gm posi additive?

Wesmanw02

iTrader: (4)

GM Dealership.

koolaid_kid

iTrader: (21)

If you use dyno fluid (non-synthetic) you need to put in the additive. Almost all auto stores carry it. If you use synthetic, check the bottle. Most have the additive already.

FLSSLS1

Torsen does not need an additive. GM had sent a bulletin out some time and that was done to quite a "rusty screw" noise. Also it is at the owners discretion. and it does not affect the durabilty of the differential. I run Mobil One synthetic in mine and it is as quite as can be. It is just a noise thing! I have noticed that synthetic seems to hold up better. IMO

dream69

So I sould be fine if I use Lucas synthetic?

FLSSLS1

that will work fine!

dream69

Ok well what if the rear is howling because the fluid was just changed and no additive was added and it just started. Could I add the limited slip additive and I stop or is the rear trash now?

EPP

iTrader: (22)

The howling would not be from the lack of additive. The additive is for the clutch packs. I'd try a heavier weight gear oil in your case. Bob

jsteele90

iTrader: (13)

werd if you use synthetic 90 percent of them have the additive already.

koolaid_kid

iTrader: (21)

They also make a 75w (or 85w) 140, which is also O.K. to run. It would be heavier and may quiet the howling.