Cascadia DT12 Transmission problem

Ultrashift in a 2014 Freightliner cascadia won't show nutral won't start just clicks 2 lines show where letter should be driver slipped the wheels and shifted from d to r then truck quit

 

Try pulling 10A fuse in battery box for a minute, then install fuse and try.

 

I have a 2015 Cascadia with DD13 engine and DT12 automatic transmission. Summer of 2022, its transmission started disengaging whenever the truck hit a pothole (not always, but most of the time). Brought to the dealership three times, they repaired a few things after treatment related such as replacing NOX sensor based on the fact that when the transmission disengaged, the Hill Decent, CEL, and sometimes DPR Re-gen lights all came on. Eventually, they found some grounding (or broken) wires to TCM (I guess).

Now, Spring of 2023, the transmission started disengaging again, even during normal highway driving with the cruise control set. This time the same dealership lowered the transmission and replaced the split pin bushing, clutch, new gasket, new filters, and new fluid. THE ISSUE STILL EXISTS !!!

The only thing is that when the transmission disengages, the engine still runs fine. If you let go of the gas pedal a little (to reduce engine RPM), the gear can usually come back within a split second. Also, the truck shows low air (won't let you engage transmission) first thing in the morning, but it won't show low air afterward.

 

GR8SONG are you getting any active fault codes when this happens? Harness chaffing on the Power Train -Controller Area Network (PT-CAN) is a know issue. This earlier post 2020 Cascadia Starter Blocked - Shift to Neutral Rough idle I put an attachment of the service bulletin that addresses a known problem. Your issue might be related. Also, post the last six of your VIN for more accurate information. Finally, everybody appreciates hearing what the fix was for problem is, whether a shop fixed or you did yourself. So please post back in forum if you get problem resolved.

 

The summer of 2022. Most of the time, when the truck hits a pothole or bump, MIL, CEL, Hill Assist, Regen, ABS, and the red STOP lights will come on briefly. The engine will be still running, but the truck will be out of gear (no gear indicated on the dash). Brought to a dealership, they did a lot after treatment-related, such as replacing DEF doser, inlet NOX sensor, and outlet NOX sensor. In the end, they replaced PT CAN wiring and fixed some grounding wires, and the truck was good for a few months.

By Spring of 2023, the truck got worse. The transmission would disengage even while driving on a highway with its cruise control set. The same dealership decided to lower the transmission, replace the split-pin bushing, replace the clutch, resurface the flywheel, and change the transmission oil and filter. The issue gets better but still happens a few times each day.

The funny thing is that it happens more often when you pull the truck off a traffic stop. In other words, it happens when you hard accelerate the truck. Most of the time, when the transmission disengages (no gear indicated on the dash), if you let go with your accelerate padel, the transmission will re-engage and will show a correct gear number on the dash.

The last six of VIN is FZ3209

 

GR8SONG, are you getting dash lights and active faults messages now when transmission disengages? Do you know what portion of PT-CAN was replaced and where specifically were the wires repaired? The reason I ask is there were bulletins out about chaffing of the harness near the Transmission Control Module (TCM) and also the more common problem by the bracket between air compressor and fuel module that I linked in my August 14, 2023 post. I as just wondering if this is more chaffing that is shorting the Power Train CAN (PT-CAN) or if some mechanical failing of transmission. A truck that spends its life in the rust belt is more corrosion and chaffed harnesses are deteriorate a lot faster. Also, I am curious where your at in terms of total miles on transmission? Are you getting close to 1 million miles?

 

I have dt12 transmission 2021 freightliner cascadia it grinds on downshift, but if it skips gears it's smooth any help also how can I post new thread