I picked up a 98 Dodge 12V Quadcab Shortbed a few weeks ago, the cruise control is a little odd, it will run up to and hold 70mph no matter what speed I set the cruise for. I can get it to drop by holding the coast button but as soon as the button is released it goes right back to 70.
Any ideas?
I'm wondering if it might not have something to do with how the shiftkit works that the previous owner installed.

 

first thing i wud do if you have access to a scanner is watch the pids for the cruise and see what its being told. otherwise id look for a test pcm to switch out and see what the results for that are