This is more a matter of curiosity than anything, as if push comes to shove I'll just get Redline MTL, but here goes:

just picked up a type-s 6mt and am looking to swap the gear oil. The part # everyone always has referenced on these forums in the past for GM syncromesh is #12377916.

I went to PacePerformance.com and when I go to view the fluid, as you can see it says that has been replaced by another GMSM fluid with part #88900399.

Does anyone know if there is any difference between these two? I'm hesitant to automatically assume the fluid with the 889 part number is the same.

 

from a search:

https://acurazine.com/forums/showthr...fluid+88900399

 

I posted in that thread that the part number did change, but that it was the same fluid. Good luck!

https://acurazine.com/forums/showpos...6&postcount=79

 

ACdelco is the new one, I tried it and it made a slight improvement.
My 6MT has only 60K.