Left wheel won't pull?

[Jeffjohnson11]

I bought a HD 870 series tractor late 80's I m guessing. Clean tractor. Problem is the only way it will move is if I press the differential lock and only the rt wheel pulls. Shouldn't both wheels lick. And pull. Why won't the left wheel pull. Any suggestions. Thank you

 

[beenthere]

Welcome to TBN

Meaning John Deere 870.
Sounds like an internal gear problem.

Been this way since purchase? Or know of an event that may have caused the issue?

 

[Roadworthy]

I agree. It sounds like a problem within the differential. The tractors I've seen normally pull on the right wheel. The differential lock adds the left wheel.