Jumps out of gear

Most likely nothing would be "bent" inside transmission, I guess maybe a shift fork could be bent. Do you know what to look for on gears as far as wear in critical area's is concerned. The teeth on the gears really don't cause much jumping from what I have learned. You need to inspect the "lugs" on the gears trhat engage into sliding collars forks attach to. Also the inside of these shift collars could be worn and unless transmission is out , and fully disassembled you cannot see the wear there. I forgot to ask if transmission shaft/gears are out of housing or are yopu doing inspection from access plates? Advise more, pictures would also help.

Edited by Chris/CT - 04 Feb 2011 at 3:48pm

use some mod clay - even playdough - and put between shifter collar and 3d gear then install shift cover and shift in 3d - then remove and inspect - should squeeze clay in to less than 1/16" inch.  Shift fork and or detent on shift rail may have to be moved to shift completely in.   3d gear or any gear should not have lateral play on shaft. 

Low oil sometime in it's life and running in 4th gear will ruin a small D-series tranny. It spins the lower gears so fast with low oil that it gaulds the bushings that the gears run on. When the bushings spin on the main shaft(which they shouldn't) it grinds out the sides of the bushings and loosens the gear pack and allows the gears to float front to rear. They should have no float. This float translates into movement so when load is applied and released while using the tractor it works the gears away from the shift coller and the gear jumps into neutral. There are lots of these trannies that the shifter doesn't allow for full engagement but this just speeds up the wear problem after the bushings are damaged. The only truse fix is a complete rebuild with good gears, bushings, bearings, and properly shimming the bearings on the shaft so there is no float in the gear cluster.