I have a 1969 L88 clone with a shifter problem in the M22 that I suspect is a linkage problem.  I can't get it into reverse consistently.  It feels like the shift lever has tilted to the left so that the left side of the shift handle hits the interior (left side) of the shift console and effectively locks out reverse (which is, of course, up and to the left).  The rest of the gears work fine and the problem does not feel like it is in the transmission itself; rather it seems that it is something in the linkage.  When the problem with reverse happens, the slot for 3rd assumes the spot for first (again, like the entire shift lever has tilted to the left).

This sounds a bit similar to a post we had several weeks ago about troubles with a reverse lock out. What you are describing sounds like an issue (or several issues) with the shifter itself. If you have a standard C3 factory shifter the only thing that has to do with the left/right motion is the shifter itself. I could be wrong but the linkage to the trans and the trans itself doesn’t have anything to do with the proper L/R function. The L/R pivot hole of the shift lever, the bottom tip of the lever and the shaft below the shifter that houses the shifter cams may all be loose, worn etc. Personally I would start from the bottom end and observe the L/R shifting motion while an assistant goes through the gears. It’s really tight under there, not sure if you spot anything or not. If the bottom end doesn’t reveal anything the next step is to go in from the top. Remove the top console plate and the lower rubber boot to expose the shifter. With the plate and boot removed, run it back through the gears and look for loose/sloppy fitting components. It’s a real pain, but the shifter can be disconnected and removed from the top. Several years ago I rebuilt a very worn out shifter on a ‘69 BB car. I replaced the shift lever, the shifter cams and the spacers between the cams. That shifter wasn’t as bad as you described but was acting very similar. Hop this helps, drop me a line via email if you wish to discuss in further detail, I think I also have some photos I could send you. Good luck and let us know what you find !!

|UPDATED|3/2/2018 1:37:15 PM (AZT)|/UPDATED|

I agree  just finished reassembling my shifter and there is not much to them, mine is still nice and snug, I would think that you could get a pretty good visual from underneath.

I agree with looking at shift/link bushings. Just for sh**s and giggles, let me ask. Does your shift lever move on hard or quick accelerations. If so check engine mounts and transmission mounts.