The transmission is slipping/dying, take it to a certified mechanic..
The synchro for those two gears is bad
There are many reasons why your reverse gears stopped working. There could be a leak or a plug for example.
it grinds grains and connected to gears
Could be the type of gears used for transmission reverse gear
Reverse and forward gears
if 1st 4rd and 5th and reverse do fine, it would have to be in the transmission. clutch problems are noticable in all gears.
The synchronizing gears don't seem to be meshing right in the transmission. If the transmission is full of fluid then it will need to be taken apart to find the problem.
6 gears not including reverse
There could be a few reasons on why your 1977 Mercury Mountaineer is not going in reverse. The most common thing that could be wrong with it would be the gears are broke.
Well in most cars there are 5 gears and the reverse. Don't forget the timing gears, steering gears and differential gears.
nope no reverse just 6 gears fast stuff
it could be the shift linkage being that both gears over there wont work