1972 Corvette Speedo Cable
 

So my cable has starting squealing pretty bad at about 40MPH. I was thinking about detaching it from the back of the speedo and lubricating the cable. What is the best way to access the back of the speedo? No air car thankfully. Drop Steering wheel? Remove gauge cluster or just work had up behind the dasha? Thanks in advance.

GM set it up to pull the dash pad holding the speedo and tach, and lowering the steering column, taking the nuts loose at the bottom of the dash and the 2 at the firewall. pull the dash out far enough to get your hand in there, I'm not sure without looking if you have a slip on cable or a screwed cable end, I'm not sure what year they changed. You can lube the cable but if you have gone this far I would suggest replacing the cable and housing, they are not that expensive and the old ones develop bad wear patterns. There a many cable lubes around everyone has their own preference, I myself like engine assembly lube, its light grease. And whatever you do don't put the cable in backwards, some guys do that so it's easier to remove the cable from the bottom. But soon after the cable will start walking in the housing and make the speedometer bounce at low speeds. The last time I replaced the cable assembly on my 77 I used a Bore scope and followed the cable through the firewall and slipped it off that way like using a piece of coat hanger or a stick welding rod, That was a lot easier but, 77 is a slip on cable with the spring tab. Good luck.

Sorry I forgot, Welcome to the forums. 1969 was the first year of the corvette slip on speedo cable, so there is a tab to push to release the cable end on the back of the spedo head.