what controls torque converter lock, and can it be changed, seems to take a long time to lock up driving normal, will lock up quicker if have tow/haul on,

 

Yes you can control lockup. Follow this write up https://www.dieseltruckresource.com/...=lockup+switch
I would be careful controlling that yourself. It can be rough on the tranny.

Here is another write up on it from cumminsforum

http://www.cumminsforum.com/forum/3r...rks-great.html

 

TC lockup is an ECU funtion based on several different parameters. It changes depending on the year of truck as all the lockup programs are not the same.

No way yet to address it directly in the ECU, but, an external switch can be used.