erikthegoalie

iTrader: (29)

I have to fill my spear 10 bolt with some fluid...75/90 I guess is the right weight, but does it REALLY need that gm additive...car sees like 50 miles a week..

Erik

95zpro

Yeah the additive keeps it from chattering especially when you corner.

speed_demon24

iTrader: (6)

I don't think you need it for the torsens.

erikthegoalie

iTrader: (29)

i dunno man when I had 4.10s installed my mech didnt add any additive...just some Mobile 1 Gear oil 75/90

alamantia

iTrader: (10)

Auburns and Eatons have clutches so you cant use synthetic oil, they get mineral oil with the additive to make the clutches happy.

Torsens have no clutches, so they get mineral oil or synthetic oil, no additive is needed. You can ad the additive to the torsens if they are noisy, its supposed to help take some noise out. GM actualy issues a bulliten on it for a torsen with a "rusty screw noise" same information is on torsens website

erikthegoalie

iTrader: (29)

alamantia, you Sir are the man
E

Crash00527

iTrader: (6)

for torsen : if installing new gears. put regular non-synthetic fluid in. than do full complete fluid change (meaning the rear diff. cover off, not just through the drain plug if you have one) at about 500-1000 miles. than put synthetic in. no need for additive if using sythetic.

if just changing fluid. take rear diff coer off. do a nice comlete clean change and use synthetic. no additve needed. especially whe using Royal Purple

cals400ex

iTrader: (27)

how can you tell which one you have from the factory? is there a code in the glovebox or something like that?

Crash00527

iTrader: (6)

the rpo codes on driver side door. should GU3,4,5,6,etc

cals400ex

iTrader: (27)

do you know what the 3,4,5, etc stand for. like which gears are which or which differentials are which? thanks

gollum

iTrader: (1)

1998 GM Service manual recommends synthetic 70/90 oil with posi additive.

koolaid_kid

iTrader: (21)

Most synthetics already have the additive in them. It will say on the bottle.

MannyZ28

iTrader: (1)

The GU codes only refer to what gear ratio the car has.

As stated in the FAQ:
GU6 = Manual transmission cars only... 3.42 gears
GU5 = Automatic transmission with performance ratio... 3.23 gears
GU2 = Automatic transmission with 2.73 gears

Most cars of 98 vintage came with the Auburn differential. Most cars 99 and younger got the Torsen.

LSGunZ28

iTrader: (8)

Yeah thats what I was thinking. I dont think the torsens need it and the trutrac is just like the torsens. But will it hurt it, if you run the additive? before I knew I added it , on 2 services and it wa sjust fine.

erikthegoalie

iTrader: (29)

i actually installed my back up 10 bolt today (8 hour job BTW)...added 2.5 quarts of Mobil 1 75/90...no additive..it said good for all diffs....itll do jus fine
erik