My brother has a 2006 Impala SS with 77k on her. He is saying that going highway speeds RPM'* seem to bounce up and down between 2k to 2500 back down to 2k again. Does not happen as frequent when cruise is engaged. He does not feel a transmission slip when it shifts. He did have 1 spark plug replaced at car max when they said there was a miss fire and he asked the tech why not replace them all. Guy said no need when the plugs are good for 100k. So I thought could be a few things, his transmission fluid does look more towards the brownish side then the redish side. Could it be because they only replaced one spark plug? He does have displacement on demand on this car as well. My brother also did some google searching and said that it sounds like this car has frequent transmission problems. I will be driving this car to work in the morning tomorrow to see for my self. Any ideas and or thoughts on what it could be? Thanks for you help guys!!

i would run some trans cleaner product in it and then change the fluid/filter with the new stuff. the oem fluid recommendations are way to long for trans and coolant. make sure the coolant is changed too. the plugs do last normally to 100k. i think though if i found one bad i would replace them all just to have them all the same. nothing to do with your problem

Try driving at a steady 50 mph on the highway, and while maintaining speed touch the brake pedal. The RPM'* should increase as touching the brake is kicking off the torque converter lock up. There is a cheap plastic plunger switch near the top of the brake pedal that activates this. If that switch is out of position it could slip now and then and cause an unexpected increase in RPM. There is a very slim chance this is causing your problem, but I thought I would throw it out there since it is so easy to check.

Well I drove it this morning and rpms were at 1800 and it bounced one time to 2grand. No jerk or any sounds. Not sure I've never seen this before.

sounds like the tcc, i think you would have to be staring at the scanner to see if it was being commanded off or what

Well I drove it this morning and rpms were at 1800 and it bounced one time to 2grand. No jerk or any sounds. Not sure I've never seen this before.

I agree with Justin. Whether related to the switch on the brake pedal or something internal to the transmission it sounds like the torque converter lock up is kicking in and out. I would get the car scanned by someone with a scanner capable of reading transmission codes.

Ok I will have my brother look into it.