Toro Wheel Horse stops randomly in 3rd gear.

Apologies in advance if this the wrong forum. Feel free to point me in the right direction.
Toro WheelHorse 12-38XL. About 8-10 years old. Bought used last season. Mower does exactly what it's supposed to do very well in all respects EXCEPT: When cutting on level ground in 3rd it randomly just coasts to a stop and stops pulling...engine still running, blade still engaged. Other gears OK. I do find that if I move it out of 3rd and then bring the shift lever back "over" the 3rd gear notch and drop the lever in and out of 3rd you can feel it trying to catch.
Bottom line, what am I in for here? What am I looking for/to replace? Just haven't stuck my head up under it yet. And if it matters I do know my way around a garage and a vehicle or two ;-) Thanks.
Kevin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You might get some responses in another newsgroup: alt.home.repair
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.