I have a Kubota B2320 with about 110 hours on it. yesterday i went to use it and it only moved a few feet before it would not go. the only way i could get it to move was in 4wd. It's a hydrostatic trans. it would move down hill, but the slightest incline or even flat and it won't move. i'm in louisa va and it's been down to 3 and 4 degrees at night. yesterday when i went to use it, it was in the 20's. i ran it for about 20 minutes and still it would go in 2wd. any thoughts.