Hard shifts in automatic transmission

After being on the highway for 30 minutes, when I exit and come to a complete stop, and begin again, the car shifts really hard between 1st and 2nd. If I shut the engine off and start it again, it will not do it anymore. It is an automatic transmission and has 30k on it. I have had it to the dealer and they have “fixed” it twice but it still does it. Any ideas I can bring to them?

It sounds like your locking torque converter isn’t unlocking.

That sounds like a software/firmware/electronic issue since it’s fixed with de-energizing and re-energizing the car. I assume that the restart was immediate and not after a cooling cycle? The mileage is a bit low for anything to be fatigued.

What year is that pontiac? What, exactly, has the dealer done?

What you need to do is take it to a local transmission shop (i.e. NOT a national corporate chain) and have them scan it for codes. There very well may be some stored for the transmission even w/out the check engine light on. A normal OBD II scanner won’t get these - you need somebody with serious equipment. (Some trans shops will do things like a basic scan for free. Others charge a fee).

Look at the invoices from the dealer and see what they say - look for codes on those invoices. (They’d look like “P1234”)

It’s a 2007, the first time the dealer replaced the “valve body and seals and gaskets” the second time they “replaced all 1-2/2-3 accumulator piston seals and cleaned valve body and other related components installed gasket-A and F-seal” This is the information listed on the service paperwork, thanks for your help!

Yeah, the restart is immediate, thanks for your thoughts!

If the torque converter were not unlocking, the car would stall when brought to a stop, like a manual transmission car if you left it in gear and stopped it without pushing in the clutch. I would suspect the problem to be electronic in nature based on the fact that the problem goes away by restarting the car. The dealer may have to reflash your PCM to solve the problem.

Sounds like an electronic issue. If you have the harsh 1-2 but it stops after cycling the key off then back on, it sounds like the computer is resetting. Heres what I would do. Drive it until the harsh shifting starts, when it does, immediately and without shutting the ignition off take it to a local auto parts store and have them scan it for codes. Remember, DO NOT shut the engine off after the harsh shifting starts because it could reset a stored code. Have them hook up a scanner with the engine still running and see if there are any codes. Post any code/s here and we can go from there.


Ok, thanks for the advise

Does any of that paperwork include any info on the diagnostic end? I.e. that was what they replaced. Does it list out what was done to get there? This would include what the trouble codes were (such as P1234) but also might include something from other transmission diagnostic procedures.