Red Line Synthetic rear fluid. Posi additive?

[Roc87]

I'm going to change the rear end oil tomorrow (who knows the last time it was done, if ever!) and I'm going to use Red Line, I've read somewhere that you don't need the GM additive? Is this true, and what happens if you still use the stuff? TIA

 

[mark b]

From my experience and others that I know, it doesn't hurt to add it. The synth's seem to be a little different between each other. Some people reported they still needed the additive, others didn't.

You could go without it and if you get chatter, add it in. I figured since I was under there getting dirty, I'd add it!

 

[FlightTest]

Most of the redline synthetics do not require the additive. The additive is a friction modifier that allows the posi plates to slip easier. If you really want to tighten your posi up, use the Redline NS (non slip) fluid. Of coarse using it will make the rear-end a little more noisy (clank and bang), but it locks up like crazy. I improved my 60 foot times a ton with my old posi using the NS fluid.

Adding the Friction modifier will make the posi much quieter, but not as tight.

 

[Roc87]

Thanks guys, I'm going to try running it for a while without it and see how noisy it is/gets