Shift Pointers
- Author: Pete Luban, ATSG Technical Supervisor
Wear in servo-pin bore can cause solenoid-performance problems, gear-ratio-error codes in 5R55N/S/W
Sometimes things are not what they appear to be, especially in the transmission-repair business. This is just such a case.
A 2002 Ford Explorer with a 5R55W transmission came into a shop with a complaint of no 2nd or 5th gear. Gear-ratio-error codes P0732 and P0735 were stored, but so was code P0775, indicating a problem with pressure-control solenoid B.
We all know what gear-ratio-error codes are all about by now, but that P0775 code – that’s a humdinger.
Some service manuals and scan-tool definitions describe this code as an electrical-circuit fault. Some manuals describe the condition as being caused by either an electrical-circuit or functional (mechanical) fault.
Of all the tech calls to the ATSG help line pertaining to gear-ratio codes as well as codes P0775 and P0745, indicating a problem with pressure-control solenoid A, and P0975, indicating a problem with pressure-control solenoid C, we have yet to find an instance in which the code was electrically generated.
These are actually pressure-control-solenoid performance codes that also generate their related gear-ratio-error codes, as indicated in the chart in Figure 1.
For example, if pressure-control solenoid B develops a fault, it will affect 2nd and 5th gears; therefore, you also should have codes P0732 and P0735, indicating a gear-ratio error in 2nd and 5th gears.
Experience also has shown that you can have a gear-ratio-error code without an electrical solenoid code, but it is unlikely that you will have an electrical solenoid code without a gear-ratio-error code. (Does that make sense?)
As you can see by the chart, each pressure-control solenoid is responsible for supplying clutch pressure in its respective gear; hence the gear-ratio-error codes.
The No. 1 problem that I see as the cause of these solenoid-performance problems as well as the gear-ratio-error codes is wear in the servo-pin bore. The 5R55N, W and S transmissions are notorious for severely wearing the servo-pin bores.
The best way to test for this condition is to back way off the band-adjustment stud so there is no tension on the band. Make sure there is oil in the release side of the servo bore, then air-apply the servo and see what blows out of the servo-pin-bore area of the case. You won’t believe how bad it can be, and in some instances the vehicle has relatively low mileage.
Excessive wear in the servo-pin bore can be repaired by obtaining repair kits for these and other transmissions from Northland Transmission Service at www.servobore.com or 715-458-2617.
By the way, the charts in figures 2a through 2g list all the codes for vehicles equipped with the 5R55N, W or S transmission, with careful attention given to “real-world” code definitions for all solenoids that are contained in these units.
