Auto Transmission

Michael Mechanic Texas Posted   Latest  

'11 IHC TerraStar 103,000 miles 

Allison 1000RDS

Truck has no known history, it was repo by used trk lot. Fuel filter and cap gone and zero battery chrg. Truck has set for a year before I was released on it. Jump batts to check fault codes… none present. Eng appears clean, no oil leaks, oil level is good, viscosity appears ok (no burnt smell) etc. Clean filter housing and install new filter, fill w/ diesel and install new cap. Replace batteries and start and run… hey, it started pretty easily and runs very good… smooth, good throttle response. So what's wrong with this truck. Still no fault lights. Truck was a tire service truck has pto hydraulics driven air compressor on it. Shift to R to stop gears and engage pto… flip air compressor switch and pumps air like a champ. What's wrong with this truck? Turn compressor off, disengage pto and shift down to drive… yep it moves forward properly. What is wrong with this truck? Shift to R to put back in location, warning starts beeping, waiting for shift then range inhibit and nothing… like in neutral. Only 103k on speedo, confirmed in ecm data. Dropped pan checked filter and oil… pristine. No metal on magnet at all and barely a film of the black particulates. Check wire harness internally while pan off looks great. Unplug and replug all connectors. Check the main connector input to trans, dry no oil. Reinstall pan and fluid and spin on external filter… the next day. Start / run do not engage pto, put truck D & R several times. Reverse works each time. The engagement seems a little bit too long getting there and a little harder than it should. Leave truck high idle for about an hour, try reverse… range inhibit and no engagement. 

My data capability is limited to just about pulling codes… no in depth interaction with tcm. Hoping someone has had this issue before with a $2. fix. ha! 

45 years working on these trucks and I'm still a worm on auto trans…. Anyhow, 'preciate some input if there's some confidence of these symptoms.

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Jeff Owner/Technician
Arizona
Jeff
   

Allison uses DOC laptop software to program and retrieve codes. You can use the shifter to retrieve codes, You could have a bad shift solenoid when the oil warms up. The code might take you in the right direction.

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Kyaw Diagnostician
Myanmar
Kyaw
 

If there is no code and no engagement occurred , it is a mechanical problem , most likely to be a hardened piston seals problem , should be able to fixed easily.

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Michael Mechanic
Texas
Michael
 

JJ… my shifter does not have digital display… R, N, D, 2, 1 if I remember correctly.

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Gary Owner/Technician
Colorado
Gary
   

Michael, I would tend to agree with Kyaw H. I'm not a big snake oil man, but for many years, I've seen seals harden on automatic transmissions and the fix I've used for the past 40 years is K&W Trans X. Trans X softens the seals and removes any varnish collection in the valve body, which really helps on transmissions that haven't been in use for a long time. Just add it to the existing…

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Leo Technician
New York
Leo
   

First off, do yourself and the shop that will end up fixing this a favor and DON'T use additives of any kind, no matter how well it worked back in the day because we aren't. Seals rarely are found to be hard with the quality of materials the OEM's use. Next, it is very possible to have no movement and no codes due to a faulty MLP sensor or wiring to it. Make certain batteries match and are fully…

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Michael Mechanic
Texas
Michael
 

MLP = M…. L….. Pressure sensor (Main Line Pressure)? Told you I was worm green… I'm guessing with "mainline". 🤔 That is found internally I suppose as I did not see any outside the pan. Thanks for the help. I'm pushing them to send it to an a/t shop…. Trying to set their expectation bar low so their no disappointed when / if I don't pull a rabbit out the hat on this auto. Should've…

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Gary Owner/Technician
Colorado
Gary
 

Michael, MLP = M…. L….. Pressure sensor (Main Line Pressure)? "MLP" refers to “Manual Lever Position” sensor (often confused with “neutral safety switch”) which is usually located on the mechanical shift lever going into the transmission valve body. Worn or contaminated MLP sensors can cause a variety of problems including drivability because the PCM or TCM can't sense gear position…

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Michael Mechanic
Texas
Michael
 

Appreciate the response guys… am in agreement with the farm out option. I did notice the MLP was located inside the pan when I had it off… well I guess you can teach an old dog something new. Happy New Year

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Michael Mechanic
Texas
Michael
 

Did farm it out no info as to culprit yet. Consider resolved.

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Gary Owner/Technician
Colorado
Gary
 

Thanks for getting back to us, Michael…

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