i have a eaton fuller 10 speed in my Columbia. when I'm heavy and only in 1st and reverse when I go to take off if I take off too had I get a clunk in the stick and the stick goes over.. now, all motor mounts and tranny mounts are fine. it is "sweating" pretty good but I don't want to pull it until I need to.

Clunking in the transmission is never good. Have you checked your transmission fluid? I had a problem with my transmission not long ago. Turns out there was no fluid in it. Where I have had it serviced they apparently never checked the fluid. In your situation, it could be several things. If the fluid is ok, my guess is that you will need to get into the transmission. BUMMER!!!!

Here's the weird part. The transmission is leaking. Went from a little low to a gallon low in 15k. The clink has been there for a little over the year. Now it's leaking but nothing showing up on the floor, clutch is not slipping. I'm due for a service in 2 weeks. That's going to be my deciding factor. The truck is a ex rental and I never touched it but change the fluid so who knows. It's just starting to shift notchy. This only happens when I'm heavy.

Hopefully, you won't need to pull the transmission to find the problem. If it is leaking, then you may need to pull it to stop the leak. If so, it would be a good time to open it up and have a look. It won't cost much more to check it out once it is out of the truck.

Sometimes its the rear end, those type of clunking noises can be tough to find sometimes, and they can be in strange places too

The mechanic had to ride on my deck plate in the yard to figure mine out, it turned out to be the power divider

i hope not.. its also erratic. its never did it empty or with a light load. would it be the power divider with it off as well? every time i use the power divider when i shut it off i smell burnt gear oil/grease smell.