if the synchro's are bad, then no, nothing will help except new synchros.

if the synchros are going out, then new synchro fluid will slow the deterioration of the them, but ultimately, no they will still go out.

if you are just low on fluid, or its very dirty, then yes, a flush/refill with help a lot

check out this thread from earlier today, might help you with some options:
https://www.tamparacing.com/forums/h...yncromesh.html