otb 15w-13 68rfe sudden drop to neutral from take off

Online Technical Bulletin

AUTOMATIC TRANSMISSION SERVICE GROUP15-W13 of 3

A late model Dodge vehicle with a 68RFE transmission may come in to the shop with a good reverse. Put it in drive, it takes off then suddenly neutralizes and stops moving forward. Reverse is still good. Cycle the ignition and the problem repeats itself. A scan tool reveals P0721 - Out put Speed Sensor Circuit Performance fault and P0933 - Hydraulic Pressure Sensor Range/Performance fault. Once the transmission is removed and inspected, no severe damage is observed. The OSS and the Line Pressure sensor are changed yet the problem persists.

The cause is due to low sprag failure. In the application chart shown in Figure 1, the low/reverse clutch holds during the initial launch of the vehicle. After 150 rpms the clutch is released placing the torque onto the sprag. When the sprag is unable to hold the vehicle goes to neutral. There are several reasons why the sprag may be overlooked. The 45 and 545RFE transmissions used a low roller clutch which rarely failed if it failed at all. The 68RFE however, uses a sprag which has been unable to hold up to the demands that is placed upon it (Figure 2). Since this was not a common problem with its predecessors, this area is overlooked. Another reason is the transmission should have gone into default mode 2nd gear limp. Electrical codes failsafes the vehicle right away. Some performance codes may need more than one drive cycle to set.

Replace the sprag. If this is a hard working vehicle or the vehicle has had performance upgrades, the new OE sprag may fail again in short order.

Suncoast Diesel and Performance Transmission has modified low roller clutch assemblies to fit into the 68RFE eliminating repeat failures. At the time of this seminar this assembly sells for $425.00.

68RFE Suncoast low roller clutch assembly.......................................................................68LRS

COMPLAINT:

CAUSE:

CORRECTION:

SERVICE INFORMATION:

SUDDEN DROP TO NEUTRAL FROM TAKE OFF

68RFE

AUTOMATIC TRANSMISSION SERVICE GROUP


15-W13 of 3

CLUTCH APPLICATION CHARTSELECTORPOSITION

LO/REVCLUTCH

UDCLUTCH

SECONDCLUTCH

ODCLUTCH

GEARRATIO

LOW SPRAGCLUTCH

FOURTHCLUTCH

REVERSECLUTCH

PARK ON

ON ON 4.44:1

3.23:1

3.23:1

3.23:1

1.83:1

1.83:1

1.83:1

1.41:1

1.00:1

1.00:1

0.81:1

0.62:1

ON

ON

ON

ON

ON

ON

ON

ON

ON ON

ONON

ON

ONON

ON

ON

ON

ON

ON

HOLD

HOLD

HOLD

REVERSE

NEUTRAL

OD-1ST

(1)-1ST

(2)-1ST

(2)-2ND

OD-2ND

OD-3RD

OD-4TH

OD-5TH

OD-6TH

OD-LIMP

(2)-LIMP

ON*

ON*

ON

L/R Clutch is on only with the output shaft speed below 150 RPM.*

Figure 1

UnderdriveClutch Overdrive

ClutchReverseClutch

SecondClutch

FourthClutch

Low/ReverseClutch Low Sprag

Clutch

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68RFE

otb 15w-13 68rfe sudden drop to neutral from take off

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