Howdy First post. Been reading any thread I can find of intermittent drive on one side, one direction only. Reverse on left side is quirky. Sometimes it will not start driving until the stick is pulled back much farther than it should have to be, for initial drive, and then it jerks in hard (both wheels move in unison, don't think it is chain problem). Sometimes it stops working at all, again only left side reverse (usually under lower throttle settings). When it does stop working if I push left stick full forward quickly, then back to reverse quickly, reverse starts working again. Sometimes it seems to work normal. Have full power and normal drive in fwd left, fwd and rev on right. Checked linkages and centering plate mechanisms, all seem OK. No leaks that I can see, hydraulic resrv. is full, not overheating. Many threads talk of checking/swapping around replenishing valves. I found a thread with a serial number (mine is 511351589) that was higher than mine and the poster was instructed the replenishing valves were on the front and back (not top and bottom). Just curious if this applies to me also? If they are top/bottom, assume you have to pull the whole assembly to get to bottom one's?? Found another thread that claims there are shuttle valves inside the hydrostatic pumps. Is this yet another control valve, or is it just another name/description for the replenishing valve? Also, is there any chance the charge relief valve (valves??) could cause a problem like this? I assume there is only one and that it would affect all drive (or none) if it was hanging up? Thanks in advance