I installed a 9 bolt and the guy I bought it off of said that it was still fairly tight. When I got it back I had taken the cover off to inspect it and I filled it back with castrol synthetic for posi's with no limited slip additive. The lube said for posi's and no additive necessary. Well the posi is no posi to say the least. It will lay down two marks every once in a while but not always. I have heard people using the posi additive or pennzoil GL5 lube. Would using something like this help me. I'm not real familiar with the cone type rear. Or should I pull it out and shim it up. Just wondering if lube would make it do this. Any experience or ideas would help. Thanks.

 

That there is a big debate here. Search the board and you will see some posts about it. For what it is worth I am running Redline lube which like yours has the additive mixed in for my 9 bolt and no problems. Put down two black streaks last night. But the guy you got it from might not be telling you the truth. Also there is a tech article on the site about shimming up the posi to restore its function.

HTH

 

https://www.thirdgen.org/newdesign/t...tservice.shtml

 

i run royal purple with additive, and i just reshimmed my rear because it was shot. get the shims from LarryBurd its cheap and easy.

 

I changed my fluid and put in Mobil1 80/90 and the GM LSD additive...very quiet and leaves 2 nice marks

Ed

 

So the additive can make that much difference in how the rearend preforms?

 

to be honest i don't know if it makes a difference in a cone type, maybe call auburn gear and see what they say, they make a cone type. If i were you i would use a good synthetic whick probably already has it, if not try it with out then add to see if there is a difference, its just a matter of removing a rubber plug!

 

Or a nice aluminum cap!!!


Ed

 

If you have the 89 GM service manual, it states use the GM additive part# xxxxxxxx. But that additive is discontinued and long gone. not replaced either.

So it's trial and error. I'm running the pennzoil GL5 withOUT additive. Next time maybe I'll try something else. I really don't see what the additive does in a cone type BW rear.

Laiky, you've seen the guts...... why would you want to reduce the amount of friction between the cones and the posi case?? That is all the additive could possibly do.

I really see NO purpose for the additve. The GM additive quites a clutch type rear by reducing the friction in the plates.

maybe someone else who disected a 9bolt can see a purpose for the additive??? I sure can't

 

actually the royal purple synthetic i use says that it includes the additive, that said i wasn't quite paying attention and i was a little bit short on fresh lube. I can say that it is remarkable smooth, and very progressive. It doesn't seem to snap the rear loose in a turn but if you gradually add power it will drift really nicely. In a strait line it leaves 2 absolutely even patches. I have no complaints what so ever!!

 

By the way, i'm not so sure that the additive actually reduces friction in as much as it smooths the tendency to chatter. I'm not an expert but i think it will still grab just as good with additive, it just wont tend to slip and suddenly lock up again, making it smoother. Just a guess.