Hi Pete

Lubrication specifications from the Tremec TKX 5-Speed service manual (from tremec.com) lists a number of products. Our equivalent is ATF FS (Full Syn.). You can also consider PRO GEAR 70W-75 (Full Syn.) that has been formulated as a gear oil with an auto trans fluid viscosity profile. Experience has shown that the appropriate gear oil can work very well to replace ATF's in gear box applications. However, do not mix these products.

If you are topping up stick to the type of fluid already in the box.

https://penriteoil.com.au/products/atf-fs-full-syn

https://penriteoil.com.au/products/pro-gear-70w-75-full-syn

Regards

Penrite Tech Support