69 Grand Prix Safe-t-trac

[greyno3]

I've got a 1969 Pontaic Grand Prix with a factory 3.23 Safe-T-Trac rear end.
I 'm going to change over to Castrol Syntech synthetic gear oil and was wondering if I still need to add limited slip additive?

Thanks for any and all input, Greg

1969 Grand Prix J Model [3rd owner]
4-bolt 428/370hp [XF]
THM400
3.23 limeted slip

[KA9MOT]

Hmmmmm... That is a good question. I think I would contact the manufacturer of you synthetic lube and ask them. They should know.

[greyno3]

I have contacted Castrol and haven't heard anything yet. It's an F5 code/3.23 10 bolt rearend. I've been told that with synthetic rear gear oil,it meets the specs for the additive. I just want to make sure.

Thanks for the help
Greg

[KA9MOT]

Yeah, and it is really difficult to tell. What is really difficult is that you could play it safe and use the additive but what if the additive is not compatible with the lube. I think I would bug the hell out of Castrol until they came up with a definitive answer.

[xxgarxx]

JUST TO BE ON THE SAFE SIDE BEST BET WOULD BE TO PUT IN THE ADITIVE ANLONG WITH THE SYNTHETIC GEAR LUBE I AM SURE CASTROL HAS WORKED OUT ALL OF THE COMPATIBILITY ISUES BECAUSE AFTER ALL WHEN YOU CANGE THE FLUID YOU NEVER GET IT ALL OUT OF THERE

[xxgarxx]

ooops sorry about all the caps just got done filling out a form at work that requires all caps so I had caps lock on

[justen]

synthetic or not, you will still need to add limited slip additive.