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transmission derate

Yahoo Message Number: 82431
I was pulling my coach out of storage this evening & heard an unusual "whine" coming from the engine area. I drove the coach for a short distance & noticed the whine was proportional with engine speed, ie: louder as rpm's increased. By the time I got to the storage lot exit the "check transmission" & "check engine" light had come on & the transmission had derated to 1st gear & would not shift into reverse. I had to continue for a short distance until I reached a point where I could turn around. I shut the engine down for a short period and then decided to restart & limp back to the storage lot. After a short distance the "whine" stopped and the coach began to run & shift normally & had no warning lights. I got back to the storage lot & checked the transmission fluid while the coach was running. Trans fluid registered OK. The whining noise reminds me of a bad power steering pump on an automobile except quite a bit louder.
Has anyone experienced a similar problem or have any ideas as to what might be causing this problem?

Would appreciate any input

Fred Compton
2005 Magna #6454

CAT C13 & Allison 4000 transmission

Re: transmission derate

Reply #1 –
Yahoo Message Number: 82437
Fred, haven't had your problem, but suggest you refer to your Allison Booklet and follow the section "Diagnostic Code Desplay Procedure".
This can be done with coach in your storage place buy turning the your ignition key to on and using the Transmission Key Pad. Make sure you have the Coach in the Neutral It helps if you have your wife or friend with a pad of paper and pen to right down the Codes (if any) as you push the Mode Button which scrolls you through the Main Code, followed by the Sub-Codes.
If there are Codes present do not Clear Them as you'll want the Allison folks to have access to them as well.

thanks, Mike 03 Allure 1st Ave. #30898
 

Re: transmission derate

Reply #2 –
Yahoo Message Number: 82470
Thanks Mike.

I did this and it appears I have a "speed sensor" issue. Doesn't seem to explain the pump noise I'm hearing however. I'll get it in for repair & see what they find

Fred Compton
2005 Magna #6454