Is Your Transmission Slipping? - Milito's Auto Repair

Reasons the transmission is slipping

If your transmission is slipping, it doesn’t necessarily mean it’s falling apart, but it does mean that it needs maintenance urgently.

These are the most common causes of transmission slippage:

• Bad fluid level or condition
• Lack of internal pressure
• Worn holding devices
• Electronic control problems

Transmission fluid level and condition

Low fluid level: Automatic transmissions depend on pressurized hydraulic fluid. A low fluid level can result in lack of pressure, preventing the gears from engaging like they should. This often results in transmission slippage.

Solution: A transmission doesn’t “burn” fluid the way an engine can burn oil. A low transmission fluid level means there is a leak somewhere. You might see red fluid on the ground under your car. Your mechanic can find the source of the leak and repair it. Once that’s taken care of, the transmission fluid can be refilled, and you can road-test your car to make sure the issue has been resolved.

Dirty transmission fluid: Metal debris and other contaminants can build up in dirty transmission fluid. This can cause a lack of pressure, preventing the gears from engaging. Dirty automatic transmission fluid can appear orange-reddish or reddish-brown.

Solution: Replace the transmission fluid and filter (if your car has one). Test the car to make sure that solves the problem.

Lack of internal pressure

Worn transmission pump: The transmission pump supplies pressurized hydraulic fluid to the transmission. A pump that is damaged or worn can result in a lack of internal pressure and transmission slippage. You may hear a whining noise, or notice a fluid leak.

Solution: Typically, the transmission must be rebuilt or replaced when the pump fails. That would be an expensive repair. The lack of pressure created by the faulty pump causes the transmission clutches and bands to slip and burn. This often results in debris contamination and subsequent damage to the transmission.

Faulty valve body: The valve body directs fluid to internal transmission components. A problem inside the valve body can prevent adequate fluid from reaching the transmission bands and clutches.

Solution: Sometimes the valve body can be replaced by itself. In most cases though, the transmission will need to be rebuilt or replaced.

Internal fluid leaks: Fluid leaks inside the transmission can come from sources such as damaged seals. This can cause a lack of pressure and make the transmission slip.

Solution: Typically, the transmission must be rebuilt or replaced when there’s an internal leak.

Worn holding devices

Deteriorated clutches and bands: Clutches and bands are made from friction material. In some cases, these devices simply wear out, causing transmission slippage.

Solution: On some vehicles, bands can be adjusted to compensate for wear. In most cases though, the transmission must be rebuilt or replaced. This is because debris from the bands or clutches can damage the rest of the transmission.

Electronic control problems

Faulty solenoids: Electronically controlled solenoids regulate the flow of hydraulic fluid for shifting. Solenoids also control transmission fluid pressure and other internal operations. A problem with one or more of the transmission solenoids can cause a lack of pressure and transmission slippage.

Solution: Sometimes, faulty solenoids can be replaced by themselves. Other times, they are integral to the valve body and the entire unit must be replaced. The transmission also could get damaged from the slipping this problem creates. In this case, the transmission may need to be built or replaced.

Transmission control module circuit problems: The transmission control module (TCM) is a computer that receives input from several sensors in your vehicle and uses it to direct the transmission. A problem with the TCM, its circuit or one of its input sensors, can result in improper solenoid operation. This can cause the transmission to slip.

Solution: In some cases, reprogramming the TCM may fix the problem. If not, the TCM control circuit or faulty sensor will need to be repaired or replaced.