That cable stretch/out of adjustment has damaged many a Lightning Rods shifter...LR's are tough, but you can break them. And good luck with finding parts. If yours is broken, talk to
88hurstolds . He used to rebuild these for folks, not sure if he's still doing that anymore. He's pretty much an expert on them.
DO NOT FORCE ANYTHING. DON'T. As mad as it can make you, if you try to bang it out of position, you may break a detent, or stretch the cable, etc., and end up with a mess on your hands. Unless your mechanic is fluent in LR shifters, I wouldn't trust them with any attempted repairs. Your dime and your time, but I personally wouldn't do it.
Try this. With the car off and parking brake on, and in a place where you can get under the car- if you can get it into Drive, see if the other rods work. If they do, you likely have a shifter to transmission cable stretch/adjustment problem. This is the most common issue with these shifters. If it's difficult to press the button down in Drive to get it out of Drive, then you need to get under the car and get a helper here to speed things up, or you'll be crawling in and out from under the car. There's a slot in the transmission lever that needs to be in DRIVE when you are in DRIVE at the shifter. If it is there, loosen the adjustment bolt on the trans lever. Hopefully you'll have enough adjustment there to do this. Then either have the helper press down the button or you'll need to crawl out and do it. If the shifter is in the right position to easily press the button down, then tighten up the cable adjust bolt and it SHOULD work. This may affect the backdrive rod to the shifter column if you still have that part for reverse lights and column lock. You might have to adjust that rod again to ensure when the shifter is in park that the column will lock.
That's the issue with these LR shifters. EVERYTHING you do to them may knock something else out of fine tune. And the LR's do not like being out of alignment, even a small amount. The stars need to be aligned (as well as your detent cross rod or whatever that alignment pin is called that the shifter rods ride on) for the shifter to operate smoothly. 95% of the time, it's a cable adjustment keeping you from experiencing LR shifter bliss.
I always need to ask this- do you have the CORRECT LR cable? It is used for the 83/84
Hurst/Olds as well as 78-82 Corvette. That's why it has a short part number. It's no longer made by GM, but there are aftermarket ones available if you can't find a new, NOS one at a reasonable price. Don't buy a used cable unless you totally don't have one. There's a reason it got replaced, right?
It's possible, but unlikely, the plunger rod "cable" inside the shifter tube may be out of adjustment. There's an allen head set screw on the "ring" for adjustment. UNLIKLELY this is your problem. Very unlikely. The Drive detent is the "tallest" one if you were to look at the detent positions. It's tall in Drive, to ensure the shifter isn't accidently pushed out of drive, because Drive allows the cross pin to line up a hole for the middle rod to have it's button pressed and moved.
And as for lubing anything on the shifter, I'd stick with graphite only. WD-40 or oil-based stuff only attracts dirt. And if you don't believe that dirt can build up on shifter components, take off your top plate and look inside after 30+ years.
Look down inside and see if you can watch what the detent is doing when you shift it. Is there noticeable wear on the detent/pin? If so, this isn't helping matters either. But you may be able to file off any burrs if that's what's hanging you up even if it's adjusted properly.
Good luck. And I mean that. Seriously. LR adjustments aren't for the weak-willed.
