I have a TRD 4 X 4 Off Road. I don't know if I should be putting the additive in the rear diff. Do all TRD Off Roads have a limited slip? Do bottles of gear oil have the additive? The stuff I just put in my diff was from Car Quest, Full Synthetic, 75W-90. The bottle says, "Full Limited Slip Performance". Does this mean no additive is necessary? Thanks. BTW, it's a very good gear lube. I've been using it for many years without any problems. Will save you 4 or 5 bucks over a bottle of Valvoline. Use this stuff, and it's like putting an extra 10 bucks in your wallet.