Both are pretty beefy! If there is oil in both of em, they probally won't need a whole lot of attention as far as the internals go.
The SM465 could probally use some work on the shifter fix any slop it has though... Here is a quick rundown of things you can do cheap / for free to help stiffen it up:
1) Put the transmission into netural, pop the shifter out and check the tip of the shifter to make sure it isn't horribly worn out. There should be a sort of D shape to it, with the shaft sticking out of the curved face of the D. If its bad then replace the shifter with a new one
2) Make sure that there are no cracks in the spot welds where the pivot ball is welded to the shaft, if there are, re-weld it.
3) Pull the sleeve off the shifter and check to make sure that the o-rings are not totally gone, if they are, replace them. If your 465 is a newer model it may have injected plastic in there instead of o-rings, in that case don't worry about it.
4) Pull the top off the transmission by reinstalling the shifter and putting it half way into reverse. Undo all the bolts and lift the top straight up. The shift forks should easily slide out from their shift collars. If they don't move the shifter further into reverse until it pops out. Take a look at the shift forks and see if all of the nylon rub pad is gone where the forks slide in the shift collars. If they are, you'd be best off replacing the forks. Unfortunately, while everything else I suggest is cheap or free, shift forks can get a bit expensive but are extremely important if you want a transmission that shifts properly.
5) Take a quick look at all the gears and make sure none of them have any excessive wiggle, broken teeth or stripped out shift collar / syncro splines. Also check the shift rails in the top to make sure they aren't worn out. They side back and forth with at least a bit of effort and shouldn't move side to side a bunch. If they do your shifter can sometimes slip between the crack that is made and get your tranny stuck in a gear.
6) Pop the top back on making sure the shift forks, esspecially the reverse fork, all slip into their proper shift collars. Pop the two roll pins where the shifter drops into out and buy new ones. Drive the new ones half way in, install the shifter, then put them in as tight as they will go with a punch.
Voila, you will have an SM465 that will never fall out of gear, and shift nice and easy with crisp, clean gates.
This work only took me an afternoon to do once I got my new shift forks in. I paid 250 bucks for all new forks, less the reverse fork.
