Depends on how good your converter is. If the converter is right lock up will not gain much but some MPH. If it is not right it can help. Now we use lockup in diesels because the narrow low rpm power band. Do lockup wrong and it will be wicked hard on parts.OK, dumb question from a guy considering a 4L80. When drag racing, if you run the clutch unlocked, are you hurting your et"s? In my current 700R, I have the lockup clutch wired so I lock it up in 4th, manually. Since I only run 3 speeds, am I loosing et's? Would the 4L80 be the same? Sorry for the hijack!
Don't expect much. Maybe when its cold but when its hot its the same.Chris, shift extension on my converter is about 600 rpm. It is a little loose on the big end as well. I have read that the Hy-Gard will help tighten a converter a bit. How much truth is there to that?