Muscle Car Review - - Tech -

For many post-1969 GM mus­cle cars with head­ers, it’s nec­es­sary to re­move the steer­ing in­ter­lock (also called the back drive) to al­low for clear­ance. The back drive was a ma­jor part of the an­titheft steer­ing col­umn sys­tem in­tro­duced in all 1969 GM pas­sen­ger cars. With the back drive, the car had to be in Park (au­to­matic trans­mis­sions) or Re­verse (man­ual) to get the col­umn to lock and al­low you to re­move the key. The lock­out mech­a­nism on man­ual trans­mis­sions also per­formed the backup light ac­ti­va­tion at the same time by ro­tat­ing the col­umn sleeve that the switch was hooked to. It’s pos­si­ble (with lots of ef­fort) to mod­ify a back drive to work, but it all de­pends upon the ap­pli­ca­tion and the head­ers in ques­tion. In or­der to get the backup lights work­ing, Hurst Shifters of­fers a bolt-in switch kit (PN 2480003).

Re­mov­ing the back drive and in­stalling the switch is easy enough, but then you have another is­sue to deal with. You have to stop the col­umn from ro­tat­ing. We came up with a clean fix that’s il­lus­trated in the pho­tos. As a re­sult, the key was easy to re­move, and as a bonus, some­thing like a col­umn-mounted tach re­mains in one spot.

One of the best parts of the fix is the fact that a col­umn-mounted tach can’t flop around with the back drive dis­con­nected. Plus, it al­lows you to re­move the key eas­ily.

In or­der to stop the steer­ing col­umn in­ter­lock from ro­tat­ing (with the back drive re­moved), we cut away most of the mech­a­nism link­age on the en­gine com­part­ment side of the col­umn (our car was orig­i­nally a col­umn shift ex­am­ple) and left just enough to mount a safety-drilled AN bolt/ lock­nut com­bi­na­tion (the bolt is drilled on the threaded end).

The mod is very un­ob­tru­sive. At first glance in this empty en­gine com­part­ment it’s dif­fi­cult to spot.

To find a spot to an­chor the mech­a­nism, we sim­ply drilled a small hole into the col­umn and fished in a sec­tion of safety wire.

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