I went and looked at the manifold bolts, and sure enough one is missing on the drivers side closest to the firewall. The misfire(s) in my truck are not bad enough to throw the SES light or to feel a lack of performance. I had the local shop data stream the computer and they found 4 very slight misfires in the motor, the worst being #5 cyl. Is that what was causing your truck's problems Tony?

 

Hi i have a 2003 chevy 2500hd with 201000 miles and my transmisson has recently started doing the exact same thing as yours. It hasnt had a misfire code that i know of though. just wondering if you ever figured out what exactly was causing your torque coverter to randomly unlock at higher rpms like mine is?

 

A lot of things can make a converter to act like this .
This is in the system . brake switch...tach..speedo..abs..vss..drac..maf..map..t ps..
ecm/computer and a bad ground ..ignition switch..bad wire in harness.
So you need to get it scanned will lead you in right direction.
Do you have abs or service engine light on?

 

I dont have an abs light on but i did have a service engine light on. i had it scanned and it was for a bad 02 sensor and too much fuel pump pressure. Would any of this cause my converter to act this way? Also would header leaks cause a misfire?