Between 40 and 50 the trans keeps down shifting and up shifting. I had the dealer look at it and the technician unplugged the firewall connections and re-connected them. (I was with him on the test drive so I know for sure that's what he did). It fixed it for a while, but it came back. For a time I was able to fix it the same way, but now that procedure does no good. Any help will be appreciated.

 

There a TSB 18-02-99 for your transmission. I would try the flash and reck.