1995 Dodge Ram Not sure of the problem

I picked this truck up 3 years ago with about 128,000 miles on it. I noticed when I put in reverse, every now and them there seemed to be a delay, and then a violent thud followed letting me know the truck was ready to go in reverse. That problem has basically gone away, but now the truck seem to rev very high between 2nd and 3rd gear and lately it tries to die when it is in a low idle. I was hoping to find out if you guys had any idea before I take the truck in. To be honest I am afraid the tranny is taking a dump and the truck is not worth the cost. Any ideas?

Kris