Chosen Solution
It starts fine and runs smooth but it won’t shift. It has a THM700R4 transmission.. Put in a new speed sensor, would like to know what other sensors I might try?
kpgklm , How is your trans. fluid is the level correct(top up to proper level with correct fluid type if not), Does the fluid look dark or smell burnt, this would be a sign of warn parts/clutch packs inside transmission, possibly over heated from driving with park brake on. Other things could be plugged filter, collapsed/pinched trans lines, Trans. pan will have to be removed to check most, valve body plugged, bad/sticking governor/plastic gear(link#1), TV(throttle valve) valve stuck/ faulty(link#2), etc.etc.. If you do not feel comfortable diagnosing or working on the truck have a good Transmission tech. have a look diagnose and estimate repair. If estimate very high consider replacing trans. with a good used from an auto recycler. 3rd link is an article diagnosing GM transmissions. Good luck. I hope this helped you out, if so let me know by pressing the helpful button. https://www.youtube.com/watch?v=PRdnl31q… https://www.youtube.com/watch?v=WLfBZeOS… http://www.lsxmag.com/tech-stories/diagn…
