My truck with 30k miles recently started not downshifting at stops. It seems to be stuck in 2nd gear, or otherwise lacks drive. When stopped in-town, at light, in drive, it will bang and shake the truck. If stopped for couple minutes, it will do this more then once. I have had it into the dealer once, they claim to find nothing wrong. It is at the dealer again, been there for a week now, they claim they haven't had time to look at the transmission.

Any suggestions?

 

My truck does the same thing on cold winter mornings, first initial stop when leaving parking lot (truck ice cold). Once trans engadges it doesn't do it again until the next morning.
I'm running an ATS valve body and have 85k on the trans. Once summer comes around it goes away. I live with it, if your trucks still under warrenty by all means demand to have it fixed. Though I'm sure it's one of those problems that never shows up when the mechanic is test driving your rig

 

one of, or a combination of, low fluid, bands out of adjustment, pressure solenoid, transducer.

 

The dealer determined that the transmission needed to be rebuilt. Don't know why yet. I will update this forum to have more details. Thanks for your help!

 

sounds to me like a locked torque converter. When the tc locks it has to unlock to downshift, if it does not, the trans will not be able to downshift.

 

I failed to mention, all this happens when truck is thoroughly warmed up into driving and stop and go traffic.