Doesn,t do it every time but when blasting across an open field WFO my transmission jumps from 4th to 5th on its own.Usually half way through 4th and especially if I hit a wet spot of mud with some resistance it will jump up into 5th and RPM obviously drop.The dogs on all the gears looked good when the engine was completely rebuilt last season.Also never noticed the problem till I went up 1 tooth on the front sprocket,I,m assuming the extra load has something to do with it?

Just curious if anyone has run into this problem or has any suggestions on what I should be looking for?Just trying to get some ideas before starting into it.