There is alot of slop between the servo piston and the adjustment arm (rear). Could the piston be stuck?

If it is stuck it can cause the reverse problem but not the third gear problem. Also would have no eng braking in low gear but it sounds like you have more then just a low/reverse servo problem. I agree it needs to come out. Ron

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In the pics it looks more or less normal. You could try a band adjust to see if it makes any diff. Back off the lock nut (without moving the adjusting screw). Tighten adjusting screw, count the turns til contact with servo, then back adjusting screw out 2 1/4 turn. Tighten the lock nut (without moving the adjusting screw) I don't think it will make a diff. but you won't know if you don't try.

Good luck.

Looks close to correct That's why you back it off after snuggingtbe adjustment but. 5/16" give or take . You can air check both servos.
Doug