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THM 4L80-E - 1994 Output Speed Sensor Eliminated

Posted on by Amos

CHANGE: Beginning at the Start Of Production for the 1994 model year, all 4WD models only of the THM 4L80-E/4L80-EHD transmissions have revised vehicle speed sensor wiring circuits. Allso find useful tools Creader VI+ and Launch X431 Master from vtoolshop.

REASON: Improved reliability when the Transfer Case is placed in 4WD LOW.

PARTS AFFECTED:

(1) TRANSMISSION OUTPUT SHAFT SENSOR (TOSS) - Eliminated on 4WD models only, and a plated steel expansion plug was installed in the case bore (See Figure 1). All 4WD models now use the Output Speed Sensor located on the transfer case as the only vehicle speed information sent to the speed buffer (See Figure 2).

NOTE: The Output Speed Sensor Bore Plug may fall out, or fluid may leak past the bore plug. Beginning on January 2 1, 1994,4L80-E, 4WD models will have a speed sensor installed in the output speed sensor bore in the transmission case.

THE SPEED SENSOR IS USED AS A PLUG ONLY.

IT WILL NOT BE ELECTRICALLY CONNECTED.

(2) TRANSFER CASE SWITCH - Previously used to energize the front drive axle thermal actuator, now has an added set of contacts incorporated inside the switch, and an added wire to signal the PCM/TCM when the am LOW range is selected. (See Figure 2).

(3) SPEED SENSOR ROTOR - Located on the Output Carrier, has been eliminated on 1994-1995 4u1) models only, as there is no longer a need for it, and is a cost savings. Care should be used to ensure that a late Output Carrier without the Speed Sensor Rotor, does not inadvertently get into a 2WD transmission (See Figure 3).

SERVICE INFORMATION:

Transmission Output Shaft Sensor (New Design) ................................................ 24203876

Figure 1: http://flic.kr/p/dWDunA

CAUTION: The Output Speed Sensor Bore Plug may fall out, or fluid may leak past the bore plug. Beginning on January 21, 1994, 4L80-E 4WD models will have a speed sensor installed in the output speed sensor bore in the transmission case.

THE SPEED SENSOR IS USED AS A PLUG ONLY.

IT WILL NOT BE ELECTRICALLY CONNECTED.

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Figure 2: http://flic.kr/p/dWxRvH

Figure 3: http://flic.kr/p/dWDuos

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