Location of the Output Speed Sensor

Berend

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Can someone tell me the location is of the Out Put Speed senor. The connector is on transfer case. On the opposite site of the connector ( rear side of the transfer case ) there is a access hatch. I have the feeling the sensor should be there.
 

Ronmar

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Your feeling is correct, that sensor is behind that small rear access cover. If you look at the sensor location diagram 68 in the 24P manual. It is part number 12 on page 3 of the diagram. Looks key shaped with two holes in the flat part of the sensor. That manual calls it a switch, but when you run the part number(29505601), Allison calls it a speed sensor...
 

Dave21

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Allison speed sensor #2950-5601

Your feeling is correct, that sensor is behind that small rear access cover. If you look at the sensor location diagram 68 in the 24P manual. It is part number 12 on page 3 of the diagram. Looks key shaped with two holes in the flat part of the sensor. That manual calls it a switch, but when you run the part number(29505601), Allison calls it a speed sensor...
Would you happen to have any instructions on how to change it ? Mine is showing a p-0734 code Do you have any suggestions or thoughts .
Thanks
 

Ronmar

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Well that is an OBD II code, but how are you getting vehicle speed sensor from that?

[h=2]P0734 Symptoms[/h]
  • Check Engine Light will illuminate
  • Vehicle will not shift properly
  • Decrease in fuel economy
  • In unusual cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be performance problems, such as dying when coming to a stop after driving on the freeway and/or misfire-like symptoms
[h=2]Common Problems That Trigger the P0734 Code[/h]
  • Defective 4th gear related shift solenoid
  • Defective 4th gear related gear set or clutch pack
  • Defective Engine Coolant Temperature Sensor
  • Defective Valve Body
  • Dirty transmission fluid that restricts the hydraulic passages
[h=2]Common Misdiagnoses[/h]
  • Engine Misfire problem
  • Internal Transmission problem
  • Driveline problem
 

Dave21

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Puzzled

Well that is an OBD II code, but how are you getting vehicle speed sensor from that?

P0734 Symptoms


  • Check Engine Light will illuminate
  • Vehicle will not shift properly
  • Decrease in fuel economy
  • In unusual cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be performance problems, such as dying when coming to a stop after driving on the freeway and/or misfire-like symptoms
Common Problems That Trigger the P0734 Code


  • Defective 4th gear related shift solenoid
  • Defective 4th gear related gear set or clutch pack
  • Defective Engine Coolant Temperature Sensor
  • Defective Valve Body
  • Dirty transmission fluid that restricts the hydraulic passages
Common Misdiagnoses


  • Engine Misfire problem
  • Internal Transmission problem
  • Driveline problem
Found this on the internet .
The vehicle's Engine Control Module (ECM), Transmission Control Module (TCM), or PCM, depending on the vehicle make and model, uses information from the transmission speed sensor, calculated against engine speed, to determine the proper gear ratio. And when this data does not match up, a P0734 trouble code is stored.


I had the fluid and filter changed at a Cat dealer here in Vegas . Drove it 6 miles and fluid was leaking all over the ground coming out of the vent on top of the transmission . Took it back twice they removed about a gallon of fluid . Last time coming home check transmission light came on the number 5 indicated on the display on the left side only and stayed in 5th gear . Cool down overnight check the level this morning still seems to be high . ( before this ) Also coming up to a stop sign it seemed to go into neutral a couple of times and then into second . So I actually had two codes p 0734 and the other one was p0796 . It is going back to Cat on Monday to see what they can find out . Truck is a M1078a1r 2007 with 4400 miles on it . Just drove from Pennsylvania to Vegas 2500 miles no problems .
Thanks for your input ([FONT=&quot]This morning it seemed to shift just like normal ?)[/FONT]
 
Last edited:

Suprman

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The one time I saw a bad speed/key sensor the only symptom was no speedometer function. The truck shifted ok. The output speed sensor on the bottom of the trans will cause erratic shifting and jittery speedo.
 

Ronmar

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Transmission speed, not vehicle speed? Allison calls all the RPM sensors in the transmission speed sensors. That second code is for a pressure control issue. The OBD codes are meant to be generic, Alison may have a more specific definition assigned to them. Have you checked with them? What model trans does the A1R come with? You should probably start a fresh thread with all your symptoms and codes. You might get more responses that way...
 

Dave21

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[FONT=&quot] Transmission is a # 06M20 E01892 3700 SP[/FONT]
[FONT=&quot] Thanks for the advice I'll go ahead and start a new thread .[/FONT]
 
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