Speedometer jumping

[Kalanic02]

I have a 2009 Chevy Malibu and the speedometer has always been a little jumpy til about 15-20mph then it steadies out but since yesterday it’s been spiking bad and causing the transmission to jerk even if it’s not switching gear just moving slightly it feel really jerkish I’ve changed the speed sensor output in the past and it honestly was doing worse then the old one so I put that one back in but the speedometer will jump in drive, reverse, and even in park I just need to know where to start looking
Nothing sounds different maybe when the jerking it sounds like it’s reving down then back up and when I tried to change the speed sensor output it was jerking switching gears

[maxwedge]

Welcome to AF. Sounds like the stepper motor in the speedo head is bad. Plenty of info online about the replacement procedure.

[Blue Bowtie]

2009 should have been a little after the problem with the instrument cluster stepper motors was discovered, but some may still have slipped through. I would agree that the speedo indication being erratic could be explained by a failing stepper motor (in the cluster) but the information that the transmission is "jerky" might tend to indicate a different problem.

If it is possible, connect a bi-directional scanner and read the VSS data while the vehicle is moving. If that is steady and the speedometer is erratic, that would almost prove a failing stepper drive in the cluster. However, if the VSS is not steady, that could explain both the erratic speedometer and transmission.

[maxwedge]

Good advice, yes the actual speedo reading in itself would not affect the trans.

[Stealthee]

The trans being jerky sounds like you have a speed sensor issue.