I know this has probably been asked and probably a dumb question. I've searched for the answers through most of the posts and even looked at the sticky that talks about how to install a manual torque converter lock-up switch but what I want to know is what it is used for. From what I've read it seems to reduce wasted torque and excessive heat as well as is better for your tranny but is this mainly for racing or do I need to do this even for highway use. I"m rebuilding a carbed 350 and I just want to know if I need to place a manual switch in order to not destroy my set-up.... any help would be great! -Gabe

Where is: "the sticky that talks about how to install a manual torque converter lock-up switch"?

Not sure that this is technically a "sticky" but this is what I found....

http://www.thirdgen.org/torqueswitch

Thanks for the link.

As long as your lock-up works correctly, you're probably better off leaving it how it is.
It does waste energy, but, as is, if working correctly, probably has better judgement as to when the torque converter should be locked or unlocked. Your transmission should last longer as is, without the manual switch, and you don't need it for highway driving, because the torque converter locks up then anyways.
Having it locked up when it normally wouldn't be might also cause your transmission to run hotter or overheat.
This could be used for racing, acting as a gear after drive, eliminating the slipping, giving you the efficiency of a manual transmission. The reason this might be done is because the 700r4 won't shift into OD at WOT.