Anyone else experiencing a flutter or RPM bounce when the transaxle shifts into 4th during moderate acceleration? This is on my 2007 2.2L, 4T45E equipped Cobalt. It seems to only happen once fully warmed and I'm not positive if it's happening on the 3-4 upshift or during torque converter lockup in 4th. There is no check engine light and other than that, it runs flawlessly and has been perfect. I have heard of one or two other 2007 owners with the same concern. No issue was found by their respective dealership service depts. I'm also not exactly sure if this is a throttle by wire problem, transmission problem, etc.. Basically the tach will bounce up/down about 500RPMs at about half second intervals during what feels like the 3-4 shift. Basically the engine goes: RRrrrr......RRrrr......RRrrrr...., tach bounces, driver bounces, etc.. until you change throttle position, then it settles right out. Other than that, she's perfect? One guy on another forum thought there might be a TSB for this. I hate to hit up my dealer unarmed.
Thanks
Joel
2007 Cobalt LS 4dr, 2.2L, Auto, bone stock deluxe poor man's package.
Update; I'm just under 12Kmi now and the torque converter oscillating in/out of lockup issue still exists, so I finally made an appointment and dropped the Cobalt off at the dealer. They had it for the day and drove it quite a bit. Their Techs were able to duplicate the concern. Apparently "GM Engineering" is aware of this issue effecting ~2007 Cobalts with the 4T45E AT. GM says it's a software problem that they are still working to debug. The service writer admitted it was way over his head, but it had to do with "serial bus #1, module 8" (something like that). In the meantime, what they did for me was download the latest software to my PCM and cleared the adaptive shift logic that the trans learned itself into. For now the problem is gone. It glides into lockup nicely w/out oscillating in/out. No cost to me and I was actually very impressed with how I was treated by this GM dealership. Basically the conclusion was; If the problem comes back, call them to see if the latest/greatest software is available. They will clear the shift adapts for me until a patch has been established.
2007 Cobalt LS 4dr, 2.2L, Auto, bone stock deluxe poor man's package.
MTPockets:
I have '06 2.4L W/4T45-E and I have the same problem. Dealer told me it is torque converter slippage and is within spec since it is NOT throwing codes. Bull!! The last time I was in there they hooked up the ODB-II reader and monitored the tranny while I drove it. They saw a 2-300 rpm "surge" at the 3-4 shift AND while in OD. It sucks. What I did notice is that they recorded line pressures and the line pressure (that controls @!#$ing) dropped into the 30's. It was a lot lower than 1-2 and 2-3. I believe a remap of the TCM or a shift kit will remedy the issue. I'm looking into that myself. There is a TSB:
POWER TRAIN:AUTOMATIC TRANSMISSION
Bulletin Number: 070730025
Bulletin Date: Oct 07
Vehicle: 2006 Chevrolet HHR
Summary:
INFORMATION ON 4T40-E (MN4) AND 4T45-E (MN5) FRONT WHEEL DRIVE AUTOMATIC TRANSMISSION VALVE BODY RECONDITIONING, DTC P0741, P0742, P0751, P0752, P0756, P0757, P1811, HARSH SHIFTS, SLIPS, NO DRIVE, NO REVERSE. ( NHTSA ITEM NUMBER - 10023942 )
Good luck.
I too own an '06 2.4L Auto with a little over 37K miles. I have had the same problem for over a year (20K miles at least) now and it's driving me crazy!!
The fact that the factory knows of the issue and hasn't put out a fix yet POs me to no end. I watched the tech monitor trans operation and also saw the RPMs run up 5-700 and the PSI drop during the 3-4 shift and TC lockup. Worst yet is even AFTER TC Lockup, it still happens which tells me it's 4th gear slipping. It even happens when in "I" mode (NO TC Lockup), Alas, it's not throwing codes so the dealer says it's within spec and too bad, nothing they can do!!! Back it the day, a good mechanic could and would fix anything!!! So....
I'm having Alex (vectorbundle@gmail.com) reprogram my ECM/TCM and hoping to boost performance and fix my Trans issues. Only thing is with full performance boost I'll have to run 91/93 octane, but it will be worth it!!
