Strange Allison occurence

[30cal4me]

This morning I backed my truck(05 2500HD SBCC) up 25 feet and then put it in park. I left truck running. About 3-4 minutes later I got back in truck and tried to back up. Truck would not move in reverse. I tried drive-still nothing. Shift to park and then try reverse and drive. Still nothing. I tried 4Hi. Nothing again. Service engine light is on dash and when I am in reverse or drive the indicator light is blinking below the gear position.

I turned truck off and restarted truck. Service engine light is still on but truck is now reversing and driving as normal. Have put 10 miles on since and truck appears fine but Service engine light is still on.

Outside air temp was 21deg. F.

Had transmission serviced(filters and fluid) by dealer 3 weeks ago. Probably less than 600mi. since service.

Anyone have any ideas?

[Mark Rinker]

We had the same exact thing happened with our 'new to us' 2006 K3500 SRW just yesterday morning...

Driver was in Grand Forks, ND, temp +5F, first morning cold start. Truck would not reverse, gearshift indicator flashing behind 'R', and illuminated dash SES light.

Took it to local Grand Forks dealership - code pulled was PO751 (Shift Solenoid D 1 Valve Performance). Service Tech found transmission was low on fluid...they added 4qts :eek: , drove truck until warm, no repeat problems. No external leaks present. Vehicle history indicates tranny cooler lines and an output shaft seal had been replaced under warranty by previous owner. (This is NOT the 2006 that I have reported having leaking tranny cooler lines in another post...that is the 2006 dually flatbed...)

Service Manager suspects transmission was not properly refilled at the tranny cooler line or output shaft seal replacement. Maybe your truck was not properly refilled at the transmission fluid service. Get the truck warm, on a level surface, and check to make sure you are full of fluid - warm range on the dipstick.

Driver continued delivery to Winnepeg and the 500 empty miles home with no further incident. The truck is back in my driveway this morning, 11F cold and plan to start it up and test reverse this morning. This light boat trip is the first long (1800 miles, 900 loaded) roadtrips we have taken with this used truck purchase - I absolutely checked the dipstick the day the truck was purchased and it was fine - fluid was in the zone, bright red, and not stinky. I am not certain that it has been checked since then, but admittedly I did't watch that truck's Allisons fluid level closely, I am more likely to pull and check them on hot days under heavy loads...but you can bet I'll be watching this one now!!!

Not sure what has transpired in the last few miles...I have put on less than 5K, nothing extreme and there are no leaks. Wondering if the fluid is simply worn out and going away under the moderate load???

Anyway - a complete flush and re-fill is in the near future for this truck, hopefully nothing was hurt with the low fluid situation.

[30cal4me]

Was able to get some heat in the tranny later in the day. I did a "Hot Check" according to the manual and found that it was 3/8" below the "COLD" mark.

Took it in to the dealer the following Monday to check level for themselves and scan for codes.

They added 1 & 1/2 litres to bring the level up.

They scanned the computer and wanted $40.00. I asked them what it told them. They said the tranny slipped due to low fluid. I told them if the fluid level was done properly by them in the first place, the tranny wouldn't have slipped, sending a code to the computer, causing me to come in for service.

Needless to say I didn't pay.