05 LLY Transmission Question

redhorse22

New member
Aug 24, 2023
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Geraldine, MT
I bought my 05 with an allison 1000 a few months ago and took it on it's first long road trip last week and had an issue I want to ask about. I was pulling a 30 foot toy hauler with nothing in it from Great Falls, MT to Rancho Murieta, CA. I was in tow/haul, and it sometimes it would just unlock the converter and it would stay that way until it came to a place it had to downshift that shift would happen normally sometimes it would downshift 2 gears then back up one after that it would work normally until the process started over. There was also a couple times the ABS light would come on, it would say service brake system on the info screen it would downshift violently a couple times and then everything would clear and work normally. I finally got brave enough to find out that if it unlocked the converter I could slow down force it to downshift to 4th with the button then let it shift back and it would work normal. Once I was setting at a light and went to start off and it popped into neutral (I guess) and the info center if I remember correctly said gear selection disabled, I put it into park and back into gear and it worked fine. Sorry this is so long and thank you in advance for you time and trouble. Kieth
 

2004LB7

Well-known member
Dec 15, 2010
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Norcal
Bad wheel speed sensors have been known to cause weird shifts and other behavior on the transmission. I'd check the sensors on the front wheels and see if you have any rub through or rust/corrosion at the hub under the sensor.

The ABS code can help narrow down which one might be at fault
 

1FastBrick

Well-known member
Dec 1, 2016
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Junkyard
ABS sensors is one issue as well the Electronic Brake Control Module it self. You would have to read the ABS codes as mentioned above to see what the specific issue is.

Neither are difficult repairs, but which direction would be dependent on the diagnostic codes stored in the ABS system.

Not all generic code readers work on the ABS system to retrieve codes. You will need one that has that capability or you will have to find some one that can do it for you.
 
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redhorse22

New member
Aug 24, 2023
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1
Geraldine, MT
Thank you for the replies, I got the codes read and it is showing U0101, U0106, U0073, U0100, P0880, C0055. So, it looks like I have an electrical issue somewhere. I added a new body ground wire and cleared the codes drove around 140 miles and U0106, P0880, and C0055 are back. Any thoughts are welcome Thanks.