1500 Runs Rough in Overdrive

[plainsdrifter]

I have a 1991 Chevy 350 Automatic. I have noticed over the past several months that,when shifted into overdrive, engine begins running rough. However, if I shift back to drive, engine will run smooth again. Sometimes I can drive in overdrive with no problems, but otherwise it gets pretty jumpy until I shift down. Any ideas on what could be causing this problem?!!

[jveik]

could it be the torque converter trying to lock up but repeatedly not being able to?

[acewelderman]

Sounds to me like your converter may have packed it in.

[slreno1217]

nope not the converter... check the plugs and wires ... sounds like a miss to me in fact i would almost gaurentee a miss.. that when you can feel a miss the most is under a pull like in overdrive.... torque converter is fine.

[MaximX]

This is a stretch but it's easy to check. I had this problem on my '95 Z71 where under light load in OD (slight grade hill) the truck would downshift into 3rd then shift back into OD very rapidly. Eventually I found the coil wire (center post on the distributor) had corroded and I was getting inconsistent/weak spark. It may not be your problem but it sounds similar.

[pies]

had the very same problem with an 85 chey. ran smooth until it shifted into overdrive, then the while truck would shutter. check the torque converter to flex plate bolts. 2 of them where loose on mine, tightened them up and the problem was gone.