Strange Noise 2005 Dmax / Allison

[k1rod]

Hi all,
My 05 Silverado has been acting a little strange. There are times I'll be driving along with no load at 70 mph on straight and level highway and all of a sudden the truck will sound either like it downshifted and the RPM's have gone up. (If the RPM's have gone up I don't know for sure because I have never been watching the tach close enough to see the change) or it also sounds somewhat like a loud electric fan kicking on. It will stay in the mode for maybe 20 minutes, then go back to a more normal sound.

Another strange thing happened once. I started the truck, put it in reverse and was trying to back out of the driveway, when I pushed down on the accelerator, the truck didn't move. It was as if I had no power. I let off and pressed again and the truck went fine. This only happened once and was several months ago.

Any help would be appreciated.

Thanks,
-rod

[Claven]

I would say the noise you are hearing is the cooling fan, they are very loud. 20 minutes seems long though, unless its hot out, and I see you are in Phoenix, sounds hot. As for the pedal thing, my partner at work had his accelerator pedal switch fail and had to replace it, so it could be that.

[k1rod]

Thanks! I thought the loud noise might be the cooling fan. I think at highway sppeds, it may be more unpredictable as to when it is going to turn on. Best, -rod

[rob@rone.ca]

Hard to believe the cooling fan should cut in on level road empty at 70 mph.

I've hauled my heavy camper up steep hills at 50 stepping on it, and never heard my cooling fan yet.

What was the outdoor temperature at the time???

It seems there are some 05's where the cooling system works different than some others.