Do I need to use the lsd additive if I'm using synthetic gear oil?

 

yes

 

Yes unless it states on the label that it is included. I know some of the synthetics already has the additive in it.

 

I had my GSL rearend rebuilt this sept. I sheared an axle drag racing. Anyways new bearing, clutch discs, and a used 4.444. The mechanic said I didnt need it. All it does is quiet down the chatter. I does nothing for wear and tear. This mechanic has been working on rotarys for about 20 years, has his own shop, and races SCCA and rents race cars and teaches drivers. So I have been using Amsoil. I don't believe that has any additives in it. He also said fill up the diff to the fill plug. Put the plug back in and then put one more quart in through the vent hole on top. I did that also, easier when the rear end is out on saw horses.

 

what about that royal purple stuff? anyone tried that?

 

royal purple and redline are good.

 

i like amsoil! i'm about to switch to their motor oil too! WOOO!

 

I couldn't get rid of the chatter in mine and I finally put valveolein and a bottle of Ford Friction Modifier in it and that fixed it right up.

 

If you get Red Line it is included.
75W90 GEAR OIL - recommended for most street driven and racing differentials. Excellent performance in conventional and limited-slip units. Also for limited-slip manual transaxles which require a 90 WT oil. Contains limited-slip friction modifiers.

Just don't add this to your manual transmission.

John