I have a Gravely PRO-200, model #988063, 50" fabricated deck WB mower It has a Peerless/Tecumseh transmission, model #700-052. Problem is it's hard to get it into 2nd, 3rd & 4th gear. You have to play with the shift lever until it will catch the gear and sometimes it will pop out of gear once you get moving. The entire shifter linkage is tight and solid. I have tried to adjust the linkage going to the transmission shift arm, but it doesn't help. I am fairly mechanical, but haven't split the transmission case open yet and would like helpful advice before I do. Could the rod and fork assembly be worn, or maybe the shift keys are shot? What should I look for? Better to just buy an entire new one? Thanks.