4L60E Shifting Manually only - Please help

[Matthew Cano]

My Father owns a 2007 Chevy Avalanche that while he was driving the other day it "fell out of gear"
 

Reverse works fine, But when you put it in Drive it does not engage like it should i believe its going into 4th and if you want to get into 1st gear you have to put it in 1. Putting it in 2 starts you in 2nd and it never attempts to downshift to 1 even at a stop.

Whats more is it also makes a wwwwiiieeer sound if you try to accelerate too hard.

the truck has 180k miles on it and the transmission recently got a new filter and oil.


Any ideas what would cause these symptoms? Ive read a few threads on other forums and the symptoms were almost identical but the causes were all over the place from: forward sprag, solinoids, pcm, ignition switch - to even a loose alternator connection and possibly even a blown fuse???.

any ideas? - hes willing to put a trans in to keep the truck going but i dont want him to spend all that money and it turn out he still needs to fix something else...

[Matthew Cano]

bump

[sefiroxx]

You probably have a bad engine sensor (ie TPS). of the computer receives bad data, or can't calculate shift points.