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Discussion Starter · #1 · (Edited)
I have had very good luck with the transmission in my ‘06 Cobalt. But have had a few hiccups in the past 28,000 miles I’ve owned it. A few episodes of hard shifting. The first time I can remember was a hard downshift, slowing from about 65 to 45, then accelerating rapidly back to speed which then the hard shift occurred. The other times have been hard shifting due to a bad battery. I have also replaced the fluid by draining the pan and filter, replacing with AC Delco Dexron IV. Fluid was pretty clean at 130,000 miles when this was done.

As of recently, October 1st to be exact, it started with some other things. It may not be related, but I had driven around to some stores after work to get my mom something for her birthday the next day, this is how I remember the exact date. After going to a coupe stores, went to Lowe’s. Came out and the car initially wouldn’t start on the first turn of the key. It instead cranked and cranked for 5-6 seconds. No anti theft problems I could see. So the second try it started but seemed flooded, idled like a second like a flooded carbed engine might do. Then it was fine. Like I said, may have nothing to do with the transmission. Afterwards drove to Whataburger and sat in line for 8-10 minutes. This is where the transmission started acting up. No codes though. But would start off in 2nd gear, shift normally into 3rd. But wouldn’t want to shift after 40 mph into 4th like usual. It held 3rd until I got to a stop light. Took off again in 2nd, hit 40 and it went into 4th, but a hard shift.

I had parked the car for a bit. After eating I took a trip to the gas station. Shifted like normal, as nothing was wrong. I believe it randomly did the whole starting off in 2nd again maybe once more and never did it again the rest of the month.

It was this past Thursday and it did the long cranking start again. The engine other otherwise is running smoothly. No shifting problems. Until Friday night. After about a 20 mile drive I noticed when I got off the highway the car was starting in 2nd. Shifts normal into 3rd, but held until over 50 mph this time. I don’t recall the speed it shifted into 4th this time. But letting off the accelerator seemed to make it shift into 4th.

So Saturday I read about some things to look for. Wiring was one. I still need to look at the G105 ground on the trans casing, I believe that’s where it goes. A visual inspection looks ok. I checked the fluid, and it did drop some from I’m guessing the axle seal that was leaking. That was fixed with a new axle, but I didn’t think I needed to check the level since it was a drip that spilled out. It wasn’t too low when I checked, but was below the overflow plug. So I added a some fluid to top it off. Before checking I drove it for about 30 minutes. Left it running for about another hour. I went to test drive it and it shifts hard out of park initially.

Before any of this, this particular problem set no codes. Although I found historical codes. I assume it was from a repair done long ago. It looks associated with a bad TCM. I believe it would have been done at a time the first owner had it. Second owner had a pretty reliable ownership.

So as I took it for the last test drive I got codes just driving out of the parking lot at my shop. But driving it after clearing them would not reproduce any codes. But would start in 2nd, shift to 3rd. But this time wouldn’t shift to 4th, even going 65-70 mph. The codes that were present are these.
•P0974 Shift Solenoid A Control Circuit High
•P0751 Shift Solenoid A Performance/Stuck Off

This solenoid seems to explain improper gear shifts and hard shifting according to explanations of the codes. The parts are cheap and available. But reading through 4T45E repairs, it might be recommended to replace the harness that goes to them, the internal harness inside the transmissionAnd also replace the other solenoids that go into the valve body at the same time. I have had what I’d say is torque converter flutter that seems to be associated with the TCC PWM solenoid. I guess this is the lock up solenoid or what makes things work with it. Again the parts are somewhat inexpensive. I don’t really like throwing parts at the car. But will probably hate removing the side cover of the transmission more than once.

I’ll see if I can do some tests with the scanner I have. It had some test that can be done on individual solenoids and even reset the TCM. But I’ll probably do a little more research before I do anything like that. I was kind of hoping it’s just the module or a ground. But doesn’t seem like it’s going to be that easy.

It looks like I can probably replace these solenoids at home. But I really despise having to work on the ground when I have a lift at work. So I’ll hopefully find some more things out or have some recommendations maybe some of you have done to your own 4T45E. If it turns out to be the solenoid, I’ll probably just do it at the shop.

I’ll also note the fluid was pretty clean when I checked Saturday. Does smell used though. So I may just want to drop the pan and have a look anyways.
 

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Discussion Starter · #2 ·
So I decided to put the Cobalt in my shop since its kind of slow right now. Started working on the car Tuesday night. Started with removing the driver side axle. Removed the control modules. Took the fuse box out. And removed the upper trans mount.

Its Wednesday night and I have removed the driver side control arm and dropped the subframe down to get the valve body cover out. Its a bit of a pain, but really was fairly simple once I figured out what all had to be loosened and moved.

So after removing the valve body cover, I started to look around and see how things looked. The shift solenoid was blistered and looked like a bloated capacitor that had gone bad. It has burned up. It’s a good thing I decided to park the car and work on it. I just hope this hasn’t done damage to the TCM. As I tried to unplug the connector, it just broke right off of the solenoid. I also accidentally broke the torque converter solenoid. I was considering replacing it anyway to see if that’ll take care of the converter lockup fluttering that has been happening since I bought the car.

I know I could have done this at home in the garage. But I’m really happy I didn’t. Doing this on a lift is so much easier. I believe the labor to have this done in a shop calls for 7 hours. I’ll have to check again but that’s what I had seen.

I’m hoping I can have this finished Thursday night. Also hoping no more problems after this.
 

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Discussion Starter · #4 ·
Yes that is on my list of things to to do. I’ll have to locate the internal harness. They weren’t too brittle luckily. Inspection the wiring it was in good shape visually.

So put it together. And somehow the connector popped off the shift solenoid B. Must have been my fault. The cover must’ve snagged it, pulled the connector off causing solenoid B to show an open circuit. Could’ve just plainly plugged it back in but had already bought another solenoid. Installed the new solenoid B anyways. Works fine now.

Bad thing was I had reassemble every thing. Had to drain the fluid and disassemble the valve body cover, again. Had purchased a new shift solenoid B. Probably would’ve been fine, but didn’t want to risk pulling it apart again.

Now the trans shifts like it should. Seems to shift better than I can remember. Before the solenoid A problem, it shifted decent. Or so I thought. So much smoother now, with quicker finer firmer shifts through all gears. With the new converter lockup solenoid, no more flutter at cruising speeds between 40-50 mph that would come and go. Seems a little more zippy, but could be in my head. But night and day difference from my observations.

The new upper trans mount make a big difference as well. Next will the front motor mount. The other two mounts aren’t torn. Will likely put new ones later on at another time.

I took quite a few long test drives. All is well. I am now able to take the cover off much quicker now so it’s a breeze for me to do again if need be.

I will need to remove the tranny later to replace the rear crankshaft seal. That should be really fun when it’s time to do it. Not really. Also the timing chain and components.

Took a bunch of pictures, so I’ll post those on a few day. Pretty worn out since I’m working on customers vehicles and having to work on my Cobalt after hours and spend my weekend repainting my own car. So I’m definitely needing some rest now. Also decided to check my alignment. Adjusted it a bit, didn’t really absolutely need it. But since we have the machine. I like to do it several times a years anyways. Hope this transmission holds up for a long while longer.
 
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