Hey Guest!
If you can shift into 1st through 4th with no issue then the hydraulics are not the issue. Reverse gear uses a shift fork separate from the other 4 gears as well as a mechanism in the rear shifter extension designed to make it hard to accidentally shift into reverse. Sounds like the lube is drying up on these parts from lack of use. Parts number 100 and 101 are the reverse protection plunger and spring.Having trouble shifting into reverse gear after car has sat for several years. Other gears work fine. Question; would reverse be more stubborn based on a poor bleed of brake system?
You don't lift up or press down on an A-series gear box to engage reverse. You have to "slap" the lever to the right to overcome the protection device and then pull back to engage the gear. Driving the car may very well loosen things up.If this is a lube issue can these parts be serviced? Moss shows them as unavailable. Would just driving the car possibly alleviate the problem?