[ron semko]

1994 GC 2wd 4.0 43RE Transmission

My overdrive is slipping out, pulled the codes and it read a "12" "Output Shaft Sensor"

1) does it make sense that this is the problem

2) where is it located

I appreciate any and all help

Thanks
Ron

[ajmorell]

First of all it is a 42RE. Are you sure it said "Output shaft" or did it say "Output speed"? If it is output speed, it is located on the driver's side, near the back end of the transmission. It is a 10 minute job.

[ron semko]

I pulled the codes from the light on the OD switch, it came up "12".

Per the list I have:

Tranny codes for 1994 OD button LED

11 Engine RPM input
12 Output shaft sensor input
13 Vehicle speed input
14 Governor pressure sensor input
15 Throttle position sensor input
16 Transmission fluid temperature input
17 Overdrive override (control) switch input
18 System voltage
19 Internal fault in module
21 Governor pressure solenoid output
22 Overdrive solenoid output
23 Converter clutch solenoid output
24 Overdrive override (control switch) lamp output
25 Internal fault in module
26 Governor pressure sensor offset drift
55 End of code transmission

Again, I appreciate the help
Ron

[ron semko]

O'pps your right, 42 RE. My typing is crap.

[ajmorell]

Jeep Grand Cherokee started using the 42RE transmission in 1993 1/2 models with the 4.0L engine. The "4" stands for 4-speed, "2" is for torque capacity, "R" is for rear-wheel drive, and "E" is for electronically controlled.

This transmission is electronically controlled using a governor pressure solenoid to vary the governor pressure. The shifts are controlled by the valve body by conventional shift valves for 1-2 and 2-3 upshifts. The 3-4 upshift and 4-3 downshifts are controlled by a solenoid. Although the shifts are controlled by shift valves for the lower gears, the higher gear is electronically controlled because the governor pressure acting against it is controlled by the transmission control module (TCM). The throttle pressure is controlled by a standard cable and throttle valve. The TCM inputs for this system include engine rpm, throttle position sensor, vehicle speed sensor, transmission output speed sensor, governor pressure sensor, transmission fluid temperature sensor and overdrive "off" switch. The TCM outputs are the 3-4 shift solenoid, the governor pressure solenoid and the torque converter clutch solenoid.

Here's how this system operates: As the output shaft begins to move, a 2-wire AC generator (transmission output speed sensor) begins to signal the TCM of the rpm. As the shaft speed increases, the TCM controls the governor pressure solenoid accordingly by a pulse-width modulated signal. Feedback to the TCM is provided by a governor pressure sensor to verify that the pressure actually changes. The pressure sensor is a 5-volt reference sensor. When the wheels are not rotating, voltage around 0.6 V is normal. As the wheels begin to speed up, the voltage should increase proportionately. If the voltage does increase, then the pressure is increasing as it should - this should be verified with a pressure gauge. This variance of pressure acts upon the shift valves in the valve body along with the throttle pressure to provide the shifts. As speed warrants, the TCM will apply the 3-4 overdrive solenoid, which is the only shift solenoid used on this system. The OD inputs are overdrive off switch, TPS, VSS, transmission temp sensor, output speed sensor and engine rpm. The torque converter clutch (TCC) solenoid will normally operate in overdrive, but the TCM can operate the TCC in third gear if the overdrive off switch is selected. Inputs for TCC include OD off switch, TPS, engine rpm, VSS, output speed and transmission temperature sensor.

The transmission temperature sensor is mounted on the overdrive/torque converter clutch solenoid assembly and provides input to the TCM. When the temperature sensor reports 30 degrees F or colder, there will be no overdrive, and below 50 degrees F, there will be no torque converter clutch. If the transmission fluid temperature sensor reports an overheating condition (over 260 degrees F) and the transmission is currently in overdrive, the TCM will downshift to third gear. The TCM will also light the LED in the dash-mounted OD off switch until the temperature drops below 230 degrees F. However, the torque converter clutch may still be operational.

This system has self-diagnostics. Fault codes can be read with a scan tool or by cycling the ignition key three times, then counting the flashes of the LED in the OD off switch. The diagnostic connector is located inside the vehicle to the left of the center console.

The default mode of the TCM is third gear. Manual shifting of reverse and second gear is possible when in default mode. Default mode happens after a fault code is set.

I hope this helps if you get one of these Jeeps in your shop!

I got that little excerpt from google. Sounds like it is the output speed sensor what you want. I have never heard of an output shaft sensor before....my guess is that in this case they are one and the same.

[ajmorell]

I was also reading this thread:
http://www.jeepforum.com/forum/showt...59358&t=247307


and it appears that the sensor is called an "Output Shaft Speed Sensor" so looks like we are both right!

[ron semko]

Thanks, I appreciate your help.

Any opinion if this may be causing my O/D to slip out ?

Ron

[ajmorell]

Originally Posted by ron semko

Thanks, I appreciate your help.

Any opinion if this may be causing my O/D to slip out ?

Ron

I'm not really sure enough to say whether that is certainly causing your problem. When mine went out the transmission just had really delayed shifts. The part is fairly cheap if I remember correctly, and since you are throwing the code for it more than likely it needs to be replaced anyways. Shoot kolak@aol.com an email and let him know what you need. He sells replacement for at a discounted price.

[greasefingers]

Since you have a 2WD both the VSS and the tranz output sensors are located on the transmission.

[ron semko]

I appreciate the help,and the pic's are great........

This is a great forum.

Thanks again
Ron

[brooin8]

I have a 94' Jeep Grand Cherokee Limited edition 5.2 V8 AWD. It seams the problem hasn't been addressed yet so I wanted to throw it out there because i have the problem. My jeep will not shift into overdrive at all. Every gear shifts perfectly except for that one problem. I read that it might be the output shaft (speed) sensor. I just want to know what kind of transmission i have because its not the same as any that i have been reading about, and also where the sensor is located. Thanks.

[blackjack12982]

Originally Posted by brooin8

I have a 94' Jeep Grand Cherokee Limited edition 5.2 V8 AWD. It seams the problem hasn't been addressed yet so I wanted to throw it out there because i have the problem. My jeep will not shift into overdrive at all. Every gear shifts perfectly except for that one problem. I read that it might be the output shaft (speed) sensor. I just want to know what kind of transmission i have because its not the same as any that i have been reading about, and also where the sensor is located. Thanks.

You have a 46RH transmission.

[brooin8]

Originally Posted by blackjack12982

You have a 46RH transmission.

What would be a reason for it not shifting into overdrive?

[bws97zj]

i have a 97 zj and i recently washed the motor bay after going out and playing in the woods. when i did that i sprayed the throttle position sensor. after that it went into limp mode and would not shift above 3rd gear and threw a output speed sensor code. i replaced the tps and where i broke off the output speed sensor female plug i just pushed the male so that the pins are in the plug until i replace it.... but both of these caused my jeep not to go into over drive... just a thought.. tps was like 50 at advanced and i put it in, in the parking lot. and fixed it. just my .02
ben