Installed a Yank 3200 in my car, and the tranny people could not tell if it was a locking, or non locking converter....After discussing this with the person I bought it from, off of ls1.tech, I found that it indeed was a locking converter. The reason the tranny people were asking, is because it would not lock up. They told me it was no problem, and the most I'd suffer from is lower gas mileage. Even after installing the tranny cooler, there's a problem. I've only noticed it happening when I've done 70 or so for a while, without the tranny shifting....Cruising on the highway, and such. When I begin my normal street driving, it will clunk hard into second, as if the tranny mount is gone. It does it into higher gears as well, though not as bad. We've checked the mount repeatedly, and the mount is fine. Any idea on what this could be?

 

Anyone....? No one has any ideas?

 

A used converter full of garbage from a failed transmission could cause this.

I doubt it but the input shaft o-ring could be cut.

 

Woot, just found out what it was. Here's the rundown, if any of you guys ever come across this, yourselves....

Due to the torque converter not locking at highway speeds, the computer senses that it's not locking up, and sends it into fail safe mode, my tranny guy tells me. This apparently causes the tranny to run full pressure, and causes the shifts to be hard as hell. So, I'm bringing it in Monday to get the lockup valve checked out. Thanks for reading!

 

You changed the converter and now the tcc won't lock up.
My guess would be on the torque converter clutch being fried rather than the lock up solinoid in the transmission going bad.
If it's going into some sort of failsafe mode it should be setting the check engine light.