What is the difference between a Tuff Torq K51A and a K51B Transmission

[Mslisaj]

What is the difference betweeen a Tuff Torq K51A and a K51B Transmission? The part numbers are even one number apart too:
880202 and 880203.
I have the A transmission in my mower and can get a K51B for a spare if it would fit. What do you think?

 

[bertsmobile1]

Not familiar with the exact tranny but the letters A ->Z reffer to external differences line the position of the various control levers, the diameter of the input pulley posission of the bypass valve et etc etc.
Any K51 will bolt into the place that any other K1 has been but you might need to be creative with the controls.

 

[tom3]

Might be a splined axle vs a keyed axle.

 

[Mslisaj]

Thank you gentlemen for your response to my question. While I am no expert by any degree I thought along the same lines as both of your responses. I got the rear tires and wheels too so I have that difference covered. But I have the trans axle now and will service it with fresh synthetic oil and have it on a shelf ready to go IF I ever need it. I certainly can build and adapt linkage if that is what I need to do but at the very least I have a working spare. I certainly appreciate your time to respond to my question and if anyone else has a more specific response I will appreciate it too but I have a spare now and that is a big deal.

Thank you again.
Lisa