Transmission question ?

[montyss]

2009 Sierra with a 5.3 at just around 50 mph the 3-4 shift will bounce back and fourth like its trying to decide to get into 4th or stay in 3d while doing this you can watch the tach fluctuate up and down sometimes a few hundred rpm . It happens when holding a steady speed of the 50 mph less or a little more with just enough pedal to hold a steady speed. If you shift it into 3d the tach will hold a steady rpm .The truck has about 35000 miles now and the transmission fluid has been changed out already just last year . Any thoughts on what it might be ?

[gmtech4]

you are up on the powertrain warranty this yr ,,,,go see the dealer ,,,,,road test WITH the tech or shop forman ,,,

 

it could be a thousand things ,to many to list here and ya cant do anything without a scanner anyways ,,,,i hope you understand

 

let us know what they say

[montyss]

yes powertrain warranty is up this August .

One other thing I know its not anything with the V4 V8 because it does it with or without the Range module installed

[NewEnglandGMC]

Just brought my 2007 Sierra 1500 SLT in for the same issue. Independent mechanic replaced crank senso and then wires and plugs. When the problem wasn;t fixed his reply was "drive it until the engine light comes on", then we can figure out what it going on.

 

I made an appointment with my local dealer service today and they say it's the torque converter. We'll see if that fixes it, but that sure seems more likely.

[montyss]

The torque convertor and a solenoid was the cure for mine , its perfect now