Allison 5sp: Have a couple of trans codes that just popped up.

[Henry95]

P0721-output speed sensor performance
P0726
I just had the TCM unplugged as I rinsed out the rad from the backside. Can anyone point me to a solution or what I should do next. Trans level is good.


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[Henry95]

I checked the input speed sensors and they are plugged in and tight.


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[Henry95]

Sorry for the lack of info. I basically lost forward but still have reverse. I had just left home so I backed up all the way home.


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[Henry95]

Checked codes again this morning and I am showing a few more.
My normal EGR codes
P0500
P0700
-P0721
P0802


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[IOWA LLY]

Since you just had your tcm unplugged, and it was working fine before.........

I would say check the pins in the TCM connector. You probably have a pin that is partially backed out, or one that has gotten loose and isn't making good contact.

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[Henry95]

I already checked that.


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[Henry95]

Pulled out put speed sensor plug apart and it was green. Cleaned that up and everything is good.


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[DieselDean]

Having same issue

Which sensor is the output shafts speed sensor. From what I've searched it's on top of the transfer case in the 4x4s but I'm looking at 2 sensors on top one towards the front of the transfer case and one in the rear. I'm assuming it's the one closest to the drive shafts but part of me thinks it's closer to the output shafts of the transmission not the transfer case. Any advise?

 

[IOWA LLY]

If it's a 4 wheel drive it's in the rear part part of the transfer case.

2wd is in the rear most section of the transmission.

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[c20elephant]

P0721-output speed sensor performance
P0726
I just had the TCM unplugged as I rinsed out the rad from the backside. Can anyone point me to a solution or what I should do next. Trans level is good.


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Remember WD-40 (Water displacement formula #40) has worked for years on this type of problem where water infiltrates when washing.

 

[Henry95]

I put electrical grease in it.


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[DieselDean]

Awesome thank you! Hopefully this clears up that problem.