There are several problems that can be resolved with an adjustment (A simple adjustment is one that can be made without removing the transmission from the vehicle.) or minor repair.
If a late model transmission (computer-controlled transmissions started becoming popular in the early ’90s) is not shifting properly, it is often the result of a computer sending incorrect signals due to a faulty sensor, or the transmission is not reacting to the computer command because of a bad connection or defective solenoid pack. These problems can be corrected while the transmission is in the car for considerably less money than a complete overhaul.
If a non computer-controlled transmission is shifting too early or too late, it may require an adjustment to the throttle cable. Since throttle cables rarely go out of adjustment on their own or due to wear and tear, these mis-adjustments are usually due to other repair work or damage from an accident. If the vehicle has a vacuum modulator instead of a throttle cable, there is an adjustment that can be made using an adjustment screw in some modulator designs. In vehicles with modulators, however, it is very important that there are no vacuum leaks and the engine is running at peak efficiency. Engine vacuum is very sensitive to how well the engine is running. In fact, many technicians use a vacuum gauge to diagnose performance problems and state-of-tune. Many problems that seem to be transmission problems disappear after a tune-up or engine performance related repair was completed.
In some older transmissions, bands can be adjusted to resolve slipping conditions. Slipping is when an engine races briefly when the transmission shifts from one gear to the next. There are no adjustments for clutch packs however.
A transmission is resealed in order to repair external transmission fluid leaks. If you see spots of red oil on the ground under the car, your transmission may be a candidate for a reseal job. In order to check a transmission for leaks, a technician will put the car on a lift and examine the unit for signs of oil leaks. If a leak is spotted at any of the external seals or gaskets and the transmission otherwise performs well, the technician will most likely recommend that the transmission be resealed.
Most of the external seals can be replaced while the transmission is still in the car but, if the front seal must be replaced, the transmission must first be removed from the vehicle in order to gain access to it, making it a much costlier job.
Replace Accessible Parts
There are a number of parts that are accessible without requiring the removal of the complete transmission. Many of the control parts including most of the electrical parts are serviceable by simply removing the oil pan. The parts that are accessible, however, vary from transmission to transmission and most transmission repair facilities would hesitate to provide meaningful warranties on external repairs for the simple reason that they cannot see if there are any additional internal problems in the components that are only accessible by transmission removal.
Transmission failure is occurring because the fluid becomes contaminated with the transmission friction material and fine metal, this friction and fine metal are getting trapped in the valve body where very close tolerances must be maintained but are compromised because friction material causes wear, additionally the fine metal is being drawn into the linear solenoids that are magnets during operation and are trapping the metal material in the very small moving components causing binding.
The transmission filter can not be depended on to remove all the suspended material that is detrimental to your transmission, service is the only way to clean up the transmission.
So you have a choice. Either believe that the manufacturer has YOUR interest in mind and not THEIRS. Or you can service your transmission and get better life expectancy. We recommend service intervals every 30,000 miles or sooner.