By the "bowden" cable, I assume you are talking about the flexible cable from the throttle linkage to the trans.(pass. side)
It is free to move in it's casing and the casing is not broken or cracked (which would let the cable expand). Appears okay.
Since you indicated that the cable controlled the shift points, I experimented with different throttle positions (increasing acceleration) to see if there was a change in the trans operation.
At approx. 85% throttle, the car actually shifted completely thru the gears. 4th engaged at 85 mph (Yipes) and 4800 rpm.
That was fun !
Immediately releasing the throttle, it DOWNSHIFTED back to 3d gear. Didn't revert to neutal and coast. Accelerating again brought a shift to 4th gear as before.
This car was not doing anything like this before it was stored, any ideas?