transmission oil
are their any issues with synthetic oil in the 4 spd.
I use the Royal Purple synthetic trans fluid.There was a thread on this a while back saying the synthetic gear lube didnt work as well with the syncros so you may want to stick to an actual synthetic trans fluid.As far as other issues go you may want to reseal the trans before using it,i put it in a fresh trans with minor seapage,old seals it may run right past.
As far as the fluid your going to put back in i have seen all of the following:
80w90 std gear lube
80w90 synthetic gear lube
75w140 syntheic gear lube
ATF trans fluid
Syncro-Mesh (Amsoil)? synthetic
Royal Purple synthetic
BG Syncroshift
I noticed no difference switching from std 80w90 gear oil to synthetic other then lighter in the wallet.Would have more effect if in a colder climate im sure.I"ll leave it at personal preference.