Updated at: 18-07-2022 - By: Lucas

Drivers have already begun to embrace automatic transmissions. In part because of their numerous advantages, interest in these devices is always rising. These transmissions, however, are more delicate and prone to malfunction than manual counterparts.

One of the reasons the unit may malfunction is if it does not shift into a higher gear or if it does not shift at all, which is extremely sensitive. There is no other option for the car owner in these situations. However, you must first verify that the transmission is the source of the problem.

Fluid deficiency is a common reason of a vehicle’s automatic gearbox not shifting into high ratios or not shifting at all. The fluid leaks because the unit’s oil seal is worn out, which is the most common cause.

Automatic transmissions that refuse to shift into high gear are a more common occurrence, however the reason for this can be traced back to the driver.

Causes why automatic transmission does not shift gears

Automatic Transmission Not Shifting I

Automatic transmissions might vary from model to model, but the most prevalent reasons of shifting issues are the same across the board. As a starting point, let’s take a look at one of the most typical causes of an automatic transmission failure.

When reversing, the vehicle engages in errant shifting in D drive mode without pausing. Engaging the R while driving forward is the same. Automatic transmissions, like the one in question, are notoriously difficult to repair.

As already mentioned, transmission fluid deficiency is another major culprit. The following are possible causes of low AT fluid levels:

  • Fluid leaks, because of worn-out oil seals. These bad seals are also caused by the use of chemicals or a poor quality transmission fluid. Leaks can also be due to the wear and tear of the deflector caps, and here overheating is the main reason for this issue.
  • Vacuum corrector faults. Inside this device, there is a special membrane that reacts to the level of vacuum. If this membrane is bad, the transmission fluid will get into the car’s motor. In this case, the unit can operate for a long time even with a significantly reduced level of lubrication, but over time it will simply fail.
  • If the pipe that connects the automatic transmission to the oil cooler is broken, all the lubricant will leave the transmission in a few minutes, so the unit will simply stop working.

Transmission oil leaks can also be caused by an inadequately tightened AT fluid cooler. Since transmission oil’s pressure is higher than that of the cooling system, it has a better chance of reaching the engine’s radiator. A leak of AT fluid can also seep into the coolant, which can cause emulsions in both the engine and the transmission when the engine is off.

Antifreeze will damage the friction clutches if it is present in the auxiliary transmission (AT). Changing the oil cooler can remedy this problem if the gears won’t shift. Also, it’s a good idea to flush and replenish the automatic gearbox fluid.

The symptoms of automatic transmission that does not shift gears

  • The automatic car drives only in reverse (R position). In this case, you need to replace the friction clutches, piston collar, clutch rings or hydroblock valve is jammed.
  • The car will engage only in first and second gear due to bad friction clutches, wear of o-rings, clutch malfunctions.
  • The transmission won’t engage in any gear at all. This is because of a failing torque converter, broken oil pump pinion, lack of lubrication in the system, clogged filter, worn friction clutches, broken collar, jammed valve.
  • The car engages in R and in the first and second gear. The valve in the hydroblock is jammed.
  • The transmission “slips” when the car starts to move. This is due to worn-out clutches.
  • When driving, the shifter is in the “D” position, but the car refuses to move when the accelerator pedal is pressed. In this case, the driver switches the automatic transmission to manual mode (if available), and the gears work well.
  • The automatic transmission does not shift higher than third gear.

The ECU (Electronic Control Unit) of the vehicle will switch the automatic transmission into emergency mode if one of these faults occurs. If an owner has any of the aforementioned issues, the first step is to run a computer diagnostic with an OBD to determine the specific nature of the problem.

How to fix an automatic car that does not shift gears

Automatic Transmission Not Shifting Into High Gear

These are some potential causes of your symptoms:

1. The level and condition of the transmission fluid.

The level and the condition should always be normal. The source of the leak must be discovered and fixed if there is not enough oil in the system. The discs should be replaced and the lubricant changed if the fluid quality is poor, mostly due to the presence of dust from friction disc wear. Don’t forget to flush the system multiple times.

2. Friction Clutch Condition

Frequent friction clutch degradation is a typical cause of transmission failure to shift The friction clutches should be checked and, if necessary, replaced.

3. Other transmission parts

Make that the valves are working properly. Replace them if they’re jamming for any reason. To ensure proper operation of the rocker and the transmission system’s electrical wiring, perform the following checks:

How to avoid problems with the automatic transmission in the future

  • Use the neutral gear only if you need to. The “N” is considered a service mode, so limit its use.
  • Warm up the automatic transmission in winter. If the AT is not heated enough, the probability of failure for certain parts is high.
  • Cars with automatic transmission should not tow anyone, since these are simply not adapted to this. Loads have a very negative effect on the unit. If you are planning to drive with a trailer, then consider this factor when buying a car.
  • Don’t try to push-start an automatic car.
  • Try not to tow an automatic car with a cable. When the engine is turned off, the fluid will not lubricate the system, and this will negatively affect the transmission as a whole. Use a towing truck instead.
  • Always use only high-quality transmission fluid recommended by your car manufacturer. Using a cheaper lubricant over time can only do more harm than good.