There are several things that can cause your manual transmission not to shift out of first gear or reverse. The most common cause is a broken shifting fork.
Some manual cars have a safety built into the reverse shift of the transmission. You need to push the shift knob down, and then over into the reverse gear.
I know on the 06 Z4 you just have to pull toward you a little harder, its kinda spring loaded reverse and first are side by side they do this to keep you from shoving it in reverse on a shift down.
Top of the transmission.. on a manual shift, it should be just behind and to the left of the shift column.
the reverse safety back up switch is located on top of the transmission next to the clutch resivior
it could be the shift linkage being that both gears over there wont work
A car with a manual or stick shift transmission.
Manual transmission is when you use the shift stick to shift to different gears in a car instead of driving without shifting gears,which is auto transmission.
The gears in your transmission may be sticking or worn out. This would cause your transmission to not be able to shift.
If it is just the shifter, try to remove the bolts at the top of shifter (UNDER RUBBER BOOT) to realign shift forks and free transmission.
Stick shift.
Well, first, you didn't specify the vehicle. Secondly, I don't think you quite grasp how transmissions work. The shift cable would be what makes a transmission go into reverse, and that'll be operated either by a manual lever (the shift column) or by an electric solenoid (in push-button transmissions).
The manual shift transmission does not have a filter.