4L60E Experts?| Grassroots Motorsports forum |

windsordeluxe Reader
1/14/16 5:45 p.m.

A customer of ours has an Avalanche that (almost) refuses to shift out of first gear. If I hook up the scan tool I can use it to perform all the shifting duties manually. There is a code for a knock sensor and no other codes. ECM is not requesting a shift unless rpms are high (4k) and you completely let off the throttle (unless using the scan tool). TPS is operating in the correct range and wheel speed sensor giving good readings. Any ideas other than new ECM? is there an input that I'm missing?

Customer suggests killing it with fire.

Thanks!

Ranger50 UltimaDork
1/14/16 6:14 p.m.

Does it move at all in manual 1 and 2? If it does, it needs to be rebuilt, as the sprag has failed and most likely could have ripped out the sun shell splines too.
How many miles on it? Anything over 80-90k, you may have welded OD solid in the input drum. That can cause sluggish take off.