I owned a 2008 2LT with the same 3.91 ratio, but quite sure I once encountered an early year 2LT with a lower ratio. Pic of the silver sticker buried in my archives somewhere.

Anyone know where the speedometer gets its info?

 

The vehicle speed sensor on the passenger side back of the transmission

 

So, on the input side? That would mean a different ratio would change the speedometer and odometer readings, but I understand you can adjust for that with the right scan tool.

 

Oldblue, I used a Banner kit with clutches. Also did the piston kit, changed all solenoids including Input speed sensor and new carrier bushing. Replaced both bands as well. I did not change the wiring harness or the feed tubes. I did air check them though and didn't find any problems. I kept the torque converter that came with the trans. When i tore it down I did not see any metal or any signs of problems. The guy I bought it from said it was good to go as is. He pulled it from the cobalt he had which got scrapped due to the notorious rust problems. He had it stored in his garage because his daughter had gotten another used cobalt. I don't think the guy would have held onto a scrap transmission and he obviously kept it for a reason so I was comfortable buying it from him.

I spent the whole weekend taking the old transmission out of the HHR and swapping the rebuilt one in. Took me two days to get it done. Put everything back together and fill transmission. put 12 quarts in because converter was empty. Let the car run like 20 mins and get in it and NOTHING. No forward at all, no reverse, heck it wouldn't even go into park. When i did put it into park there was grinding. Sounded like the park mechanism trying to engage but just wouldn't. I tried everything. unplugged wire harness and reseated several times but it didn't work. It got dark and I called it quits till this morning.

Dropped subframe enough to get cover off thinking maybe I forgot to hook up the manual shift lever but it was hooked up. I put that transmission together correctly. Went over it with a fine toothed comb. Looked over diagrams and illustrations repeatedly. So, pulled it back out and put the old transmission back in which was an all day project. Had to call off work. Still sitting here trying to go over everything in my head. Thinking of a couple things, I did take the pump apart to replace all the seals inside of it. On the service instructions it advises not to disassemble the pump. It is pressed together and wondering if it can't prime now after putting it back together. I also noticed when i was plugging in the wire harness it was slightly difficult to plug in. I didn't force it and it did go. I checked the pin arrangement and it matches identical to the old transmission in car.

Last thing i'm wondering is maybe I resized one of the teflon seals too small. Had to resize a couple of them after installing them. I just did the zip tie with old soda bottle method. Worked great and there seemed to be decent resistance while still allowing me to assemble everything. Seems to me either a communication problem with wiring or lack of pressure for whatever reason be it pump or a seal. But very strange it did nothing at all.

so i spent the money to rebuild a trans and can't even use it. I could speculate all day long whats wrong but it's not like I want to do trial and error with a transmission. I don't want to drop a trans and put another in for the 3rd time and if it's still not right have to drop it again! I did swipe all the solenoids from it and put them on the old trans before I put it back in. Can a transmission place "bench test" a transmission that's not installed?

 

Did you fill the torque converter on the bench? 12 quarts is 5 quarts to many, to start off. No movement indicates to me the fluid transfer pipes have a cracked weld or didn’t seal properly.

 

Oldblue, no i didn't bench fill the converter. Everything i read said 13 quarts dry for HHR. I remember saying to myself that's a lot of fluid! Regardless, the old transmission is back in. I had already filled this one before reading your post. I checked the fluid level and fluid pretty much just shot out of the check hole. I let it come out till it was just dribbling out. Car was running and warmed up so i'm sure it's a proper level now. I did put new solenoids on the old trans before putting it back in. Not sure why but it is not shifting well into 4th. Kind of shifting hard. didn't do that before the new solenoids. Hoping maybe just the TCM needs to learn the new solenoids.

The rebuilt trans is back in my shed. Tore it back down tonight and tested everything and all assemblies with pistons working well. All the seals are great too. I did examine the transfer pipes and tested with air and they all hold. No broken welds or cracks. I did put new O-rings on those and only used trans fluid to keep them in place when I attached them. Like you said, maybe they slipped out of place when i tightened them down. When i took them off to look at them the O-rings were not in the indentations where they belong but I just assumed they had come out of place because of removing the pipes.

Also tested the wire harness for continuity from plug ends to connector at harness and they are all good. Even if the harness was bad i'm reading there should still be 3rd gear and reverse. I'm going to assume that means even if the harness on the car side wasn't plugging into the harness on transmission properly I should have still had 3rd or reverse and I had nothing. So that tells me either those pipes or something with the pump. I followed a diagram when i put the pump back together. Maybe the vanes were worn and i didn't put them back how they were. I don't think those pumps are that picky though. they just have to get oil circulating which is thick.

Also, the rebuilt appears to be the same gearing. I counted all the teeth on each sprocket on the chain and also the pinion and ring gear and both are identical. It all matched up to the old transmission which i had tore down to inspect when i had it out. Putting the old trans back in the car is not how I wanted this week to be. Plus now it's acting up locking up in overdrive. You gun it to get out of OD and it immediately slams back to OD again. But the car drives.

 

So I'm pretty sure I found the problem. Of course I don't want to admit it but it's 100% my fault. It seems in my rush to get the rebuilt trans back together and put in, I missed putting the sun gear back in the final drive assembly. I dropped a screwdriver in my work area and it rolled under a work bench. When i bent down to pick up the screwdriver I saw it. The sun gear was underneath the bench. It must have rolled off at some point and i didn't see it and completely missed it when assembling. Just goes to show no matter how meticulous you are people make mistakes.

I think it's safe to say this is why I had no gears. I'll bet you the line pressure is just fine and the assemblies were doing what they're supposed to. But without that sun gear in the diff the car is going nowhere! Not looking forward to the 3rd transmission swap in a weeks time. All on a driveway with jack stands and a transmission jack! I'm getting too old for this!

 

Good you found the sun gear, we’re gonna kick back and wait till you reinstall that transmission and test it.

 

Want to know everyone's opinion on this. Would i be ok to test the transmission after installing it without putting subframe back on and just reconnecting the driver side trans mount? I would leave the engine brace on too. When i say test I mean connect the lines and fill it up and start car and see if it has gears not actually drive it. I'm tired of putting it all back together just to tear down again. I've been removing entire suspension both sides to give me complete freedom to move around on the driveway. Who wants to be hitting their head on crap or even breaking or bending something. You almost have to anyways on the drivers side to get your transmission jack in and out.

 

So long as it’s supported properly, just for a minuet or two , no longer.