whine at 50 MPH 2001 GMC savanna

[mephius]

Just purchased a 2001 GMC savanna 1500 with 5000 miles on it!!!! (low miles legit!) at exactly 50 MPH with engine pulling consistently there is a loud whine that sounds very much like a rear end gear whine. mentioned it quickly to the dealer he says may be muffler harmonics due to 3" exaust!, I dont buy it!!!!! Says he has heard that before and installed a baffle in exaust with no better result from baffle. (thats because it probably wasnt that)

he says to test by putting in neutral at 50 and see if it goes away. Well, hard to do because as soon as you stop pulling, the sound stops. I think because you unload the gear train. I tried to duplicate RPM while the truck was rolling at 50 in neutral to see if it really is exaust and NO whine!!( even though it is hard to get it exact)

will have him look but my gut says REAR END GEAR LASH set wrong.

Anyone out there have similar problem?....If so please fill me in on your experience.

Thanks .........................

[bigtruck21]

did you ever figure out what it was?