SECOND & THIRD GEARS LOCKED TOGETHER

Probabilty that you can correct this problem without removing the gearbox pan = 0.00001%

Seriously, the good news is that you've probably just had something "slip" in the shifting mechanism linkage inside the gearbox (it's a bunch of small castings that are "squeeze-clamped" onto some sliding cylindrical rods), and do have two gears selected at the same time (which will lock the rear wheels). Of course, you should definitely inspect the shift shaft flexible bushings to make sure that they aren't what caused you select two gears at once (if they are in poor condition). You could try removing the shift gate and seeing if the shift lever can move sideways when in the forward or aft positions, but you'd be just as likely to mess things up as improve them (You weren't doing something like this when you caused the "problem" were you?) I know that these photos look complicated, but once you actually see the shifting mechanism inside the gearbox, it's a fairly straight-forward arrangement:

When you move the shift lever left-right in the center position, the forked arm 1 passes over the three stack levers (and no gear is selected = neutral).

When you move the shift lever fore-aft, it operates one of the three levers, depending on whether the stick is left (R-1), center (2-3), or right (4-5)
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drove to a warehouse, parked in gear, left in that position for 3 years


Brilliant...

 

I'm not exactly sure what you mean by this (as the pan in front of the gearbox pan is the engine pan), but, if you have the gearbox pan off:

1. see if the three levers are lined up when the shift lever is in neutral (they should be)

and

2. There are three castings like the one labeled "4" in the photos. When in the middle between the teeth on the synchro rings (like in the photo) neither gear is selected. If all three are not in their middle position when you have the three levers lined up like in the photo something has slipped, and you can just try manual putting each casting "4" in the middle position -- when all three are in the middle position your rear wheels should be free.
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Not sure if you are talking about the three stack levers being "all lined up" or the three "4" castings being in their proper (middle) positions. With all three "4" castings in their middle position (no gear selected), are the rear wheels are still locked up, or do they spin freely?

With all three "4" castings in their middle position (no gear selected), are the three stacked levers lined up vertically? If they aren't, that's needs to be corrected. Disconnecting the shifting linkage outside of the gearbox won't be of much benefit IMO -- what you need is for the three stack levers to be lined up vertically when the shift lever is in neutral and for all three "4" casting to be in their middle position. If you can achieve that (so the shift lever can move freely from left-to-right in the shift gate), but you still can't select some gears, that's a more serious gearbox problem.

 

Don't see how removing only the gearbox would be less work than removing the gearbox+engine (and I don't know if it's even possible).

I'd certainly make sure that (after 3 years of storage) that the rear brakes, nor the rear wheel bearings, aren't the real problem, but good luck with the fix (and please let us know how it works out).

 

Sure, we just need a set of sky hooks, and a cutting torch

 

Jack up the rear of the car. Try turning a road wheel. Rock it back and forth while looking at the exposed gears. What part(s) move? If the answer is none, put the cover back on the tranny and go look at the brakes and rotors. If the brakes are free you should hear and feel the slop in the diff and gear sets.

 

Mark, you may want to take some pictures of the gear box and post them, someone may see something you didn't.