Just as the header states, the Ford 5R55 Transmission can have an N, S or W behind those numbers.
The 5R55 is a rear wheel drive 5-speed that appeared on 1999 and later vehicles.
The 5R55W came out in the 2002 and later Ford Explorer and Ford Ranger models.
The 5R55N appeared in the Jaguar S-Type and Lincoln LS and in 2002 in the Ford Thunderbird. In 2003 the Thunderbird and Lincolns switched to the 5R55S that had the Select Shift (allows drivers to shift like a standard without the clutch).
The 5R55S without the Select Shift is used in the 2005 and later models of the ford Mustang.
Although the 5R55N is very similar to the W or S models, only a few parts are interchangeable.
The common problems we see on these units are the excess wear on the case or valve body.
We receive numerous calls about these where someone has rebuilt the transmission, yet still experiences the same symptoms.
Transmission case premature wear occurs on the Overdrive and Intermediate Servo bores. Apply oil comes up through the servo pin bore and through the hollow pin applying the servo. This requires the the pin to seal in the servo pin bore, as well as the release oil that both servos require. Over time the number of apply and release wears out and the pin no longer can seal properly. The Overdrive servo bore will usually have more wear due to it being used for second and fifth gear. As the servo leaks, which will result in a pressure loss, that lacks the pressure to hold either the band completely applied or release it fast enough to prevent the band from being burned up.
These can be repaired without replacing the case. By drilling the servo bores and installing a "cesleeve" to compensate for the wear, elimates the need to replace the case. The Brass sleeve has proven to be more durable then the aluminum case giving you stability. You don't want to use a "used case" as the possibility of the bores being worn in a used case are more then likely.
The Valve body can also have excessive wear, most often seen on the TCC (torque converter clutch) modulator bore, or main regulator bore.
As in the case situation, the high duty cycle of use wears down the bore reducing clutch and servo pressures.
Although the PCM (power control module) will try and compensate with adaptive strategy, the excess wear will cause gear ratio or slipping codes.
A Valve body repair or Update kit will usually correct these problems.
These are just a couple of most common problems seen on these transmissions and not all these problems may have this problem.
Gear ratio error Codes are very common on these transmissions due to servo pin bore wear occurring at a very low mileage in some cases.
You can have a gear ratio error code without having an electrical code (Solenoid) but unlikely that you will have an electrical circuit code without a gear ratio error code.
Having a proper diagnostic by qualified techs will eliminate the guess work and save you major expenses in the rebuilding of these transmissions.