Has anyone had success with using synthetic transmission fluid in a manual transmission? I changed the gear lube in a T18 4 speed to synthetic gear lube and also changed the fluid in my 49 3600 T5 tranny to 50W synthetic gear lube. Both trannies now have shifting problems like the syncros aren't doing there job. I'll put regular gear lube back in the T18 but what Is best for a NWC T5.
