(Updated on September 23, 2022)
The transmission is the part of your vehicle’s powertrain that transfers power from the engine to the wheels. If you have a problem with your transmission, you may not be able to drive the car.
Here are some common reasons you may not be able to shift into gear.
Why Won’t My Car Go Into Gear?
Some components that cause shifting difficulties have nothing to do with the transmission at all. Before you try to rebuild or replace your transmission, here are some common causes of shifting problems for both transmission implementations.
1) Bad Shift Interlock Solenoid
A shift interlock is the part of your transmission that locks you out of other gears when you shouldn’t be able to use them. For instance, you only want to be able to shift out of park when you’re pressing the brake pedal.
A shift interlock solenoid is the electrical device that tells the interlock when to unlock the shifter. If you have a bad shift interlock solenoid, you won’t be able to shift out of park or neutral into any gear.
2) Bad Brake Switch
The brake switch is a special switch that tells the car when you’re pressing the brake pedal. This switch is especially important in an automatic transmission because automatics creep when they’re in gear.
In order to prevent undesired vehicle movement, manufacturers require that the brake pedal be pressed before you shift out of park. If you can’t shift out of park, try pulling and testing the brake switch. A bad brake switch commonly comes with a check engine light and brake lights that won’t turn off.
This is an easy DIY job if you have a multimeter, as most brake switches are easily accessible. They are commonly located near the pedal assembly.
3) Bad Shifter Linkage
Many automatic transmissions use a cable to change gears inside the transmission. This cable is connected to the shifter lever.
If this shifter linkage were to become detached, the shifter would move easily between gear slots, but the actual gear inside the transmission would not change.
4) Low Clutch Fluid
The vast majority of manual transmissions use a hydraulic system to disengage the clutch. If your clutch fluid is low, you may not be able to exert enough hydraulic pressure against the pressure plate to disengage the clutch.
When the clutch is unable to disengage, it is very difficult (and sometimes impossible) to shift into gear while the engine is running. Clutch fluid level can be inspected from the clutch reservoir in the engine bay. Some vehicles share one fluid reservoir between the brake and the clutch.
5) Clutch Pedal Assembly
Sometimes your car won’t go into gear simply because there’s an issue with the clutch pedal. Perhaps the pedal assembly is bent, preventing full disengagement of the clutch. Check the pedal for proper operation.
6) Broken Pressure Plate Spring
The pressure plate is the part of the clutch system that separates the clutch from the flywheel and allows them to spin at different speeds.
If you have one or more broken pressure plate fingers, the clutch may not be able to disengage fully, even when they hydraulics are working correctly.
7) Bad Slave Cylinder or Clutch Fork
A slave cylinder is the part that transfers the pressures from the clutch hydraulics to the clutch fork when you press on the clutch pedal. The clutch fork is the lever that physically separates the pressure plate from the flywheel.
If the clutch fork becomes detached from the slave cylinder, or the slave cylinder goes bad, your clutch will not disengage at all. This means you would not be able to shift gears while the car is running (unless you were already moving, where clutchless shifts are sometimes possible).
8) Bad Shifter Cable
Like automatics, many manual transmissions use a shifter cable to transfer the motion from the shifter in the cabin to the transmission. This is especially true of front wheel drive cars with a transverse engine and transaxle.
If your shifter cable goes bad or becomes detached, you will be unable to shift gears. The shifter may move freely with little to no resistance if this happens.
9) Honorable Mention: Bad Synchros
Synchronizers or “synchros” match the speed of each gear you select to the output shaft in the transmission as you shift from one gear to the next.
If your synchros are bad, this may cause difficulty shifting into specific gears. Typically you won’t see an issue shifting into every gear, but only specific gears as the synchro wears out in that single location.
Cost to Repair
The cost to repair a transmission that won’t go into gear varies greatly depending on the root cause. A bad shifter cable, low clutch fluid, and a bad brake switch are all very cheap to replace, and you will likely be paying less than $100 to have these issues repaired.
The other issues are more expensive. Any time the transmission needs to come out of the car, you will incur significant labor costs. Expect to pay $800 minimum if the transmission needs to come out as part of the repair. A transmission rebuild or replacement could cost thousands.