Torque Converter Clutch Disconnect Switch

[toobroketoretire]

As I wanted my '71's TH700R4 to perform just like it does in my '82 I made a torque converter clutch disconnect switch that operates off of manifold vacuum. I used a $5 lumber yard switch and a HEI vacuum advance can and between the two parts my torque converter's clutch will unlock when the vacuum drops to about 3" Hg. At first it didn't unlock quick enough so I added a helper spring to "fine tune" it. Now when I am climbing the steep hills in 4th gear a heavy throttle will unlock the clutch and give me about 500 rpm more; making it unnecessary to downshift into 3rd gear. I have made several of these for friends but I now use a Standard VC-240 to achieve the 3" Hg unlock.

Under normal operation the vacuum advance forces the switch closed but when vacuum drops to about 3" Hg the vacuum advance can "releases" and allows the switch to open; unlocking the clutch. Simple, huh?

 

[toobroketoretire]

The really cool thing about my vacuum-operated t/c clutch disconnect switch is it'll allow up to 500 more rpm when I want to pass a car. Rather than downshifting into 3rd gear it'll disconnect the clutch and away I go. Then if I need even more power I can always force the 3rd gear downshift. And then when higher vacuum returns the clutch will lock again.