A normal automatic transmission should engage smoothly and firmly when you move the gear selector into Drive. If your transmission hesitates to engage when you move it in Drive, or it flares or slips when upshifting, or it slips while driving, it is not functioning properly.
Transmission slipping may be produced by several things:
* A low fluid level
* Low internal fluid pressure
* Faulty pressure regulation or control
Type Of Transmission Slipping Caused By Low Fluid Level
This is one of the most frequent and easily fixed problems that can cause transmission slipping. For the torque converter to transmit engine torque to the transmission, the converter must be loaded with fluid. Also, there must be enough fluid to create the internal pressure needed to engage the various gears. If the fluid level in your transmission is low, the transmission may hesitate for a few seconds before engaging when you first put it into Drive or Reverse.
The first thing you need to do is to inspect the fluid level in the transmission. If you don’t know where the dipstick is for your transmission, look in your Owners Manual.
To acquire an accurate reading, the fluid in the transmission must be warm. This may need driving your car for a few miles to warm up the fluid.
Also, on most cars the fluid level must be checked while the engine is idling and the transmission is in PARK.
If you inspect the fluid level with the engine off, the dipstick reading will NOT be accurate and will read higher than normal since some of the fluid that would normally be circulating inside the transmission and torque converter will have drained back into the transmission pan. That’s why the fluid level must be inspected while the engine is idling and the fluid is circulating in the transmission. Set the parking brake and make sure the transmission is in Park before you inspect the fluid level.
If the fluid level is not found between the ADD and FULL marks, add the specified fluid to SLOWLY bring the fluid up to the FULL mark.
Add only ONE PINT of fluid at a time before rechecking the dipstick reading. On many transmissions, it just takes about one pint of fluid to bring the level up from the ADD line to the FULL line. You do NOT want to overfill the transmission since this can cause fluid leaks and fluid aeration (that will make additional shifting and slipping issues).
The type of ATF specified for your transmission is often inscribed on the dipstick cap or the dipstick itself. The type of ATF needed can also be found in your Owners Manual.
If including fluid and bringing the fluid level up to the FULL mark fails to eliminate the slipping problem, the issue is one of the following causes.
Types Of Transmission Slipping Caused By Low Fluid Pressure
An automatic transmission must produce a certain amount of internal pressure to work properly. If the pump is worn or the fluid filter or pickup tube is obstructed, the transmission may not produce enough pressure to engage and shift normally.
A worn pump is bad news since it means the transmission will need to be rebuilt or changed.
A plugged transmission filter, on the other hand, can be remedied by taking out the transmission pan, draining out the fluid and changing the filter with a new one. Be sure to clean the pan thoroughly before it is reinstalled on the transmission.
If a filter and fluid replacement do not cure the slipping problem, your transmission may have a worn pump or an issue in the valve body that regulates pressure, engagement and shifting. This will need the skills of an experienced transmission technician to diagnose.
A Transmission Slipping Caused by Faulty Pressure Regulation or Control
The internal pressure inside an automatic transmission is regulated by a pressure regulator or pressure solenoid valves. Part of the diagnostic procedure is to link a pressure gauge to the transmission so control pressure readings can be taken with the transmission in different gear positions while the engine is idling. Lower than normal readings in any gear position will show which circuit is malfunctioning. The fix may only need replacing a pressure regulator valve or control solenoid or sensor. But more often than not, the fix will need rebuilding or changing the transmission.
On newer electronic transmissions, the status of the various transmission control valves, solenoids and sensors can be shown on a scan tool. This usually needs a high end (expensive!) scan tool or a factory scan tool that can display all of the transmission data PIDs. A scan tool is also helpful for diagnosing torque converter clutch (TCC) issues. It will show you if the clutch is engaged or not, and you can compare transmission shaft speeds against engine RPM to see if the torque converter clutch or transmission is slipping. A basic code reader or scan tool is all you require to check for transmission-related codes.
What Automatic Transmission Repair Options Are Available?
The average motorist is at a demerit when it comes to automatic transmission diagnosis and repair since transmissions are very complex and not well understood by the general public. In many situations, a repair facility will recommend rebuilding or changing a high mileage transmission rather than attempting to repair it because they know from experience such repairs are often a temporary fix. Sooner or later you will be back with another transmission issue.
Do not waste your money on transmission fluid additives if you are having a transmission issue and are hoping for a cheap fix. It won’t happen. The damage has already been done and you will probably require a new transmission. Additives can slow down fluid leaks in older transmissions. They can equally provide additional wear protection for transmissions that are in good working condition. But there is no miracle cure in a can.
If your transmission has gotten to the end of the road and requires to be rebuilt or changed, you have four repair options: a new transmission (very expensive and may not be offered from a new car dealer), having your old transmission rebuilt, changing your old transmission with a remanufactured transmission, or changing your old transmission with a used transmission from a salvage yard.
A used transmission can save you money but you want to ensure the used transmission has been tested and comes with a warranty. Guarantees on used transmissions typically starts from 30 days up to 1 year – but do NOT cover installation labor. If you are shopping for a good used transmission, try to find one from a low mileage car that has been wrecked.
A rebuilt or remanufactured transmission should equally come with some kind of warranty. Typically, these start from 90 days up to 3 years (longer is better!). If a shop is rebuilding your old transmission or changing it with a reman unit, the guarantee will often cover installation labor, too – which often costs as much if not more than the transmission cost itself.