4T45E Problems - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 5 (permalink) Old 09-20-2017, 05:22 PM Thread Starter
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4T45E Problems

2010 Cobalt 89K
Started off shifting hard between 1st-2nd, codes read TCM, replaced it and programmed
Still shifted hard so I grounded the TCM and it did not do anything different, then code came up for 1-2 shift sylinoid, so I went ahead and changed both 1-2 and 3-4 sylanoid, everything in the case looked good except for axle seal had to replace it. Topped off trans fluid.
Started it put it in R and it went forwards, all gears went forwards.
Messed around with shifter and gear selector/safety neutral switch and then it wouldn't move, took range selector off put it back in time and reinstalled, had no gears at all. Pulled pan & filter off to see if any tubes were damaged/ disconnected and looked good. Added fluid in and started up revved up to 3grand and tires moved slowly then engine light came on for TCC torque converter sylanoid. Tore everything back apart and noticed the case must have caught the sensor and broke it when I reinstalled it the first time, replaced it and double checked everything it all looked good. Reassembled and added the fluid and tried it. Even tried disconnecting battery for a while, putting the old TCM in place and I am stumped. I can shift into all gears, BUT it wants to go forwards in all gears at very high RMS, enough to turn the wheels at 10-20mph with no weight (on lift) I really don't believe the trans is bad, I understand they only come with 1/8 inch of pads on bands but the trans worked great other than hard shifting.
Any ideas?
Could the range selector / neautral safety switch cause this? I know sounds strange but before I spend the 80 bucks on it I'd like to get opinions
Any help would be greatly appriciated!!!
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post #2 of 5 (permalink) Old 09-20-2017, 05:58 PM
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Did you have any other symptoms originally? Most often problem causing hard shifting is lost of communication between TCM and BCM. This is usually resolved by re-seating the connectors on BCM . Occasionally the TCM/ECM fuse needs to be swapped because of corrosion or pitting.

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post #3 of 5 (permalink) Old 09-20-2017, 06:07 PM Thread Starter
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Only thing I can remember is it shifted hard going up hills and sometimes revved up high RPM before it would do a shift. The car has been having this problem for over 6 months now and was just afraid of breaking a transaxel with the jerk of the shift so I made the wife park it 6 months ago, just finally got enough time to deal with it. I did check all fuses, not just with a volt tester but actually pulled the fuses to make sure there wasn't a broken one that may be jumping arc. I will take the connectors off the BCM and make sure they are clean/corroded free and put electrogrease on them, i may have done this already but can not remember. I checked alot of the wires to see if any were broke, rubbed anything in that nature and havn't found anything. Any particular spot or does anyone have any diagrams where i could probe or back probe certain wires to test these sylanoids I changed?
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post #4 of 5 (permalink) Old 09-21-2017, 05:37 PM Thread Starter
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Checked the connectors and looked great there is no corrosion anywhere, also put a new gear selector on it today and still acting the same, all forward gears with some torque behind the spin until it warms up then it lags the torque, looks like I will do a tranny swap and hope this works.
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post #5 of 5 (permalink) Old 09-21-2017, 06:07 PM
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What are the codes? Did you swap out the ECM/TCM fuse?

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