I have alot of old trannys. i dont want to keep buying trannys cause it seem that all the used ones grind gears. I was wanting take the trannys i have and make a good one. how do you know if the part the syncro slides down on is good. Most of the ones i have are warn but not chipped of broken. some of them have burs on them.

 

You'll have to look at the engagement teeth on the gears, if they're worn badly they'll grind or you'll have have engagement issues. Check the clearance on syncros between the syncro and the gear, check the sleeves and hubs for wear, if the sleeve is chewed up it will grind.

 

Whats considered "chewed up" or worn badly, on the gears & sleeves?

 

Sleeves themselves where the meet the engagement teeth on the gear, engagement teeth that are rounded or severly worn one way. Syncro rings you have to check as well, sometimes the teeth look pretty good but they have no clearance between the gear (pads on the inside of the syncro ring are worn) Also if its a situation like the OP is in the gears and sliders get hot and turn soft. Normally you can't touch a gear with a file, they're hardened, if you can mark them with a file they've gotten too hot.