# 727518. With these four parts you can convert your 727 transmission to a 518 overdrive transmission with locking torque converter. What this kit does is makes a 518 transmission shift without a computer. Lets say you drive an average of 400 highway miles per week, at that rate you could save as much as $1000.00 per year on gas, not to mention the 31% reduction in RPM. Your new 518 will have automatic shifts into overdrive and lock-up, no toggle switch needed. Now with an adjustable vacuum switch option.