A friend of mine just got a 65 Imperial, and when you put it in reverse the park sprag isn't disengaged all the way and it clatters like hell. I've never messed with pushbutton transmissions. Thanks in advance guys.

park sprag is activated by the cable in the tail housing. there is a fastener with a nut that holds the cable in place. back off the nut until the cable can move freely in the housing. pull the cable out until the park sprag is fully disengaged and retighten the fastner nut.

NOTE: When performing the above adjustment the shifter must NOT be in Park.

Also, just backing off the nut on the cable lock stud won't usually loosen the cable, you need to tap on the end of the of the stud to loosen it.