i really need help and figured anyone might know what the problem if any is: i was towing today with my '01 LB7 and noticed something strange. after i got it running (tow/haul the whole time) i hit a grade and the truck downshifted but it made a funny noise in front of me kind of like a hissing or blowing sound . i didnt lose any speed or power just had to deal with the noise but if i put it into drive and it got into 5th gear it sounded fine any help greatly appriciated i am supposed to start towing a lot here soon and dont want it to be a big issue Allen
Should be normal if anything was seriously wrong it would have popped a trouble code fropm what your saying it just sounded like a fan clutch enguaging or a turbo spooling. I know the Allison in my work truck will whine when I go uphill sometimes if would also help to know the speed and rmp's and percent of grade to really nail down what you have going on. I wouldnt be worried cause it sounds normal.
speed was 55 when it first started and then it did it until i had off loaded the trailer,rpm was about 2300-2500 when it first happened. and the grade was about a 4 but like i said it still did it after i got onto flat land any other ideas??? thanks Allen
More than likely just the tranny nothing to be worried about unless its gets hot or really starts slipping but to me it sounds normal.
