I Agree ... way too much difference for tires size only.

As far as movement forward goes you are traveling farther at a given RPM with a higher Aspect Ratio tire ie: Tire Revs per mile are less.

Trans/torque converter lock up issue very possible but as long as were guessing ... Maybe an errant runaway tach ??
Probably not if your HHR is also noisier.

SF

 

Could the trans/torque converter issue be a sensor? I ask because we can't pull any codes. I'm going to disconnect the negative battery terminal today when I get home from work. Hopefully the computer reset itself. I just think it's weird that it started doing this all of a sudden.

I forgot that I had the trans fluid changed because the pan gasket was leaking. This was after the first of the year. Maybe mid-January. I usually do stuff like that myself but I didn't have time so my wife took it to the shop that works on their company trucks and vans. I wonder if they under-filled or over-filled the trans. They did use Dexron-VI because they called me and told me that the required Dexron-VI fluid was expensive.

Transmission doesn't shift hard, make noises or slip. It shifts into all gears, goes into reverse fine and functions normally in the I position as well as L.

Trying to cover all of my bases before I take it in to a dealer and they start changing parts, guessing at it because they can't figure it out either or when they can't pull codes they say I need a new transmission. I work for a dealership, unfortunately not a GM dealership. I know how this is going to go.

 

Under filling could be a cause, I guess. There is no dipstick! The fluid level control port is on the passenger side. It needs to be checked car level, engine running, trans in park/neutral, fluid temp 104F. Fluid should come up to the hole, in other words, after you get all of those things done you add a bit of fluid until it drips, then wait til it stops dripping.

Transmission codes can't be accessed with the normal OBDII code reader.

Are you agonizing about the dealer because you still have a drivetrain warranty, or because you think (erroneously) only they can work on it?

Just noticed it's a 2006 forget a drivetrain warranty, any shop would be able to work on the trans.

 

I just don't have a lot of faith in dealerships. It's just the way they have to recover time and bill all of the hours the techs have on a work order. I see it from the inside. I work for a dealership. The level of incompetance with techs is unbelievable and the service managers can't write off the stupidity so you end up paying for a lot you shouldn't have to.

I have a bad feeling that this will be one of those times where they can't or won't diagnose the problem so it will be a bunch of R&R of parts guessing at what servo is causing the problem or immediately telling me I need a transmisson and tgen they sublet the job to someone else.

I just have an attitude towards dealership service departments.

 

That is why I suggest you go to a different shop. You got no warranty, thus no reason to go to GM.

 

I think you are bouncing around to much with ideas without eliminating some of them. That's part of the protocol to diagnose.

Have you tried driving at a steady speed while watching the tach.....say at the 3500 RPM you described. Without changing your gas pedal position, shift into "I" mode......still watching the tach. If it drops 500-700 RPM the converter is working. So it probably is not that....thus eliminated.

Now you start looking elsewhere. However, if the RPM's DO NOT REDUCE, then you do have converter problem of some sort.


But as mentioned above, that RPM is still to high for the speed mentioned even if the converter is NOT working. Should be in the area of 2300-2500, working, and maybe 3000 not working.

 

fwiw: Running those taller tires will make your speed-o read slower that your actual speed..

So you are actually traveling faster than you think..

I would try & compare your speed with GPS or something like that..

 

OOPS, you are right. I was thinking he got 50s instead of 55s.

 

http://imageshack.com/a/img13/6895/003vid.jpg

My 06 auto with stock tires at 70 mph.

 

Thanks Old Lar