High pitch whine heard when slider window open while driving. Poss. fuel pump?? on 1997 GMC 1500 Pickup

Truck has a camper shell and sound comes up btwn the cab/box/camper shell. Was making the whine at 55mph from new for several years. For the last 10 months it happens at 55,60,65,70mph; but much louder. Can hear pump come on when ignition turned on; truck starts everytime; no loss of power on acceleration, 105K miles on truck. Always did it before at 55mph; now it's intermittent. What else could make this whine; rear end; drive shaft; transmission??

by in Windsor, CA on August 28, 2012
2 answers 2 comments
ANSWER by on August 29, 2012
poss dry u joints or any of the things you mentioned. if you can't find it seek diag and est
COMMENT by on August 30, 2012
Thanks for the reply. I had a '72 GMC and it had fittings on the U-joints; this one doesn't have any. This one has a two-piece drive shaft and no fittings at the joint. A friend mentioned possible differential gears getting noisier. Had my garage do a 100K mile service and change the differential case fluid. Can't find anything else in that location that would cause this whine. Est. for pump and sending unit $500-$950. Question: Is there a suitable fuel pump that could be mounted on the chasis, installed in the fuel line, outside the fuel tank and before the fuel filter? Wouldn't have to remove the tank and the problem is fixed.
COMMENT by on August 31, 2012
WHY DO YOU THINK IT IS THE PUMP? PUMP RUNS ALL THE TIME ENGINE IS RUNNING WOULD MAKE NOISE SITTING STILL, NOT JUST WHILE DRIVING. CHECK DRIVESHAFT SUPPORT BEARING, EVEN WIND NOISE CAN PLAY TRICKS ON YOU!!!!! AS FOR A REPLACMENT PUMP I DON'T KNOW OF ANY OTHER THAN OEM. HAVE MECHANIC RIDE IN BACK AND LISTEN.
ANSWER by on November 23, 2014
have the same code on my truck gmc 97 it is because the cat converter is off mine and the code cant be cleared it will show a number 6 cylinder misfire as a result but its no big deal