Transmission problems

[jcook!]

I have a T7074 with just over 1000 hours. The transmission seems to want to jump into 4 wheel drive when going forward. It grinds and the 4wd lever jumps back and forth. If I pull back on the lever it will stop. I have adjust the linkage, but it doesn't help. With linkage disconnected i can turn shaft and it feels like it is engaging and disengaging. Anyone have experience or ideas with this?