Meet the 68RFE
the torque converter, add 12 quarts of ATF +4 to transmis- sion.
The only recommended fluid for
the 68RFE is MOPAR +4 oil. Using any other blend may cause shift prob- lems that can only be fixed by using the proper oil (figure 3).
Pressure Tests
To pressure test this transmission,
you must have an accurate tachometer and pressure gauge. Test gauges must have a 300 PSI maximum range wher- ever pressures exceed 100 PSI. The torque converter clutch apply
and release ports are located on the right side of the transmission case. There are two methods of test-
ing line pressure. The first method requires using a scan tool and adapter that allows you to monitor perceived pressure (scan data) vs actual pressure (pressure gauge). The second method (not available
on all applications because of mount- ing issues) requires a special adapter oil pan that allows you to tap into each clutch pressure port located on the valve body (figure 4). The scan tool can be used to read
line pressure from the line pressure sensor. The second method is to install Line Pressure Adapter 8259 into the transmission case and then install the pressure gauge and the original sensor into the adapter. This will allow you to compare the
scan tool and gauge readings to deter- mine the accuracy of the line pressure sensor. The scan tool line pressure reading should be within 10 PSI of the gauge read- ing.
Another method of testing
hydraulic line pressure involves removing the valve body pres- sure test ports and installing the parts of the valve body pres- sure tap adapter and one or more 300 PSI pressure gauges (Miller Special Tool #8258-A and #C-3293SP) (figure 5 and 6).
With methods 1 or 2, here’s
how to test the pressure: • Check the transmission fluid level and condition (you can only test the con-
6
Figure 7
GEARS May/June 2010
dition with the oil pan removed).
• Check the shift cable adjustment. • Raise the vehicle, and install the pressure gauge and adapter.
• Install a tachometer to monitor engine RPM.
• Check line pressure with the engine at 1500 RPM, while shifting the transmission into park, reverse and drive.
Compare the scan tool line pres-
sure reading with the desired line pres- sure and gauge reading. All three read- ings should agree. If the gauge reading doesn’t match
the scan tool reading, you’re dealing with a line pressure sensor problem.
If the scan tool reading doesn’t match the desired line pressure, look for a pressure control problem (Figure 7) (oil level, filter, pump regulator valve, PCS solenoid, etc.). Actual line pressure while in gear
will vary, based on minimum learned line pressure. Minimum line pressure starts at 40 PSI and “learns up” to the minimum pressure to hold the clutches in an applied state. That’s all for now; look for more
as the 68RFE becomes a more common sight in the transmission bays.
Figure 6
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