SC3005SP

Hello,
I have a 1992 5Speed SC300. I have some questions about the transmission which has roughly 140,000 miles on it. Whenever I shift 1st to 2nd and so on it grinds. Depending on how fast or slow I shift it grinds either slightly or a lot. It just recently started maybe a month ago. Is there anything I can do to fix this? Is this a sign that I need a new transmission? Also if I do need a new transmission should I get a regular 5 Speed or just spend the extra money and get the 6 Speed? Oh and if I got the 6 speed what else would I need to source to put it in my car. (ex: Driveshafts, Clutch, etc...)? I suppose I cans earch for the answers for that final question but since were on the topic I just thought I'd ask.
Thank you for info,
-Brian

SC300T

I'm not a transmission expert by any means, but I imagine its just the synchro that is perhaps going bad. I'd try Redline MT90, see if that changes anything. MT90 has been great for my shift feel.

Other than that, I think people have some success rebuilding the 5spd pretty cheaply. The W58 is pretty popular.