Brando5641

iTrader: (3)

2007 4l70 wont shift out of first gear. I can watch commanded gear in HPT. It will show the gear change from 1st to 4th but nothing happens, when you leave the gear selector in "D" the engine will fall back to idle when you let off the throttle running down the road but if you manually pull it down into 3,2,or 1 it will engine brake. Tried pulling the TCM fuse to see if it would start in 2nd but it wont. Engine will run all the way to the limiter without issue and trans doesnt slip. Input and output speed sensors are working.

Is it possible to have a stuck valve causing this issue?

I bought the truck with the issue so i dont know if there where any issues leading up to not shifting. Fluid looks good ( on the stick )

bbond105

Most likely a worn 2-4 band. You can measure the 2-4 servo cover travel and if a good bit more than .125” the band is worn beyond its service limits. You can check the 3rd gear clutches by unplugging the electrical plug on the passenger side of the trans. With this unplugged the trans should start off in 3rd gear.

Brando5641

iTrader: (3)

Just dropped the pan. Fluid is super smoked. Metallic brown. Going to get a rebuild kit on the way.