problem with transmission(or maybe not)

i have a 2006 prerunner double cab automatic with 84k on it. when it downshifts out of 4th gear into 3rd it will hesitate and then jump forward.
it only does it when its down shifting. i was wondering if this is the transmission or maybe hopefully something less serious. also when i come to a stop light about ten seconds after i come to a complete stop with my foot completely on the brake the truck jumps forward on its own. it feels like i am being bumped by someone. these problems just started and i was wondering if anyone has had any of these problems before and could contribute some feedback.

 

Welcome to the site!

Sorry you're having issues.

Not had the problem but, hang out a while and I bet someone has some input.

 

At the stop light, do you have your heater or AC on? It very well could be the ac compressor clutch engaging and disengaging. For your downshift from 4-3, try disconnecting your battery overnight and reconnecting in the morning. This will fully de-energize the computers in the truck and your ECT will have to relearn your driving habits. Might work, might not, it's free though.

 

Sounds normal to me. My '99 did both of these all of the time. When it downshifts, do you have your foot on the gas (like going up a steep hill)? Usually when you're accelerating up a hill, the transmission downshifts due to a pressure drop in the valve train or when you push the gas pedal down more than half way. The hesitation would be the truck slowing down while going up hill. Do to the drop in pressure, the trans downshifts and lurches forward to react to your foot on the gas.

The lurching forward at a traffic light is most likely the AC compressor kicking on. Mine did that all the time.

Now I have a manual trans so I don't have this anymore but I'm sure nothing has changed.