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  1. #1

    Default Strange noise/rev issue please help.

    I have a 2001 Chevy Silverado 4x4 with the 4.8 liter V8. I have a leveling kit, 3 inch body lift and 33 inch mud tires, as far as performance parts i have dual exhaust, high flow cats to a y-pipe (no muffler), a K&N 77 series cold air intake and a edge cts programmer, which for the past 6 months or so has been on the performance setting, using 93 octane gas. Truck has about 140,000 miles

    The issue that most concerns me is recently i have noticed a sort of whining sound from the engine compartment, almost similar to the sound of an electric pump, etc. it increases with rpms but is generally droned out by the exhaust, however it is very aggravating and easily noticeable, especially from outside of the truck, my friend thought it sounded like it could be the heater coil but i dont know, i have also noticed that the floorboard on the passenger side is often wet, but i noticed this a while ago and doesnt change whether i run heat, AC or nothing. Does anyone have any idea what this could be?

    My other problem that i have noticed is at cruising speed, around 57-60 mph when i am putting my foot down just a bit to accelerate slightly but not som much that i down shift, just enough to speed up some, the engine will sometimes start to "jumpup an down" so to speak about 200-300 rpms. It is NOT the transmission slipping because when it revs up you can feel the truck speed up a bit. its almost as if i am pressing and depressing the pedal but my foot doesnt move.

    sorry for being so long-winded but any help would be greatly appreciated, this truck is my baby and im just out of ideas as to what the issues could be.

    01 Silverado 4x4
    4.8 liter V8
    high-flow cats to straight pipe duels
    leveling kit and new 3 inch body lift
    33x12.50 bfg mud terrains
    16x10 american racing bajas (outlaw II look-alikes)
    20% tint on driver and passenger windows and 5 in the back
    95 Chevy/GMC mutt project mud truck
    83 GMC Sierra to be fixed up (grandpa's old truck)

  2. #2
    Sr. Engineer
    Join Date
    Oct 2010
    Indianapolis, In


    A couple of thoughts on the water, windsheild leak or more likely the heater core and maybe the condensate drain from the A/C. Sometimes alternaters will whine a bit but I would start with the drive belt idler and tensioner as probable causes. Remove the belt and that will eliminate the power steering, fan, alternater, tensioner, idler and of course the belt as causes. If it dissapears then you know where to start loooking, if not then maybe a vacume leak. As for the engine jumping up and down in RPM... I have no clue.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

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