SD help with humming after bagging

[s10layinlow]

So I am fully bagged and drive a 98 2.2 reg cab. At 60 -70 I get a humming noise that sounds like its coming from my floor or front end. I stops some when I let off gas and starts again when I speed up. If I go over a bump on the highway it changes pitch as I bounce. My pinion is good in the rear. What could It be.?

[Tim99Zr2]

i think i heard it could be your pinion bearing in the axle.. im not 100% sure thou, my dads truck does it. my buddy said his did it, and that was the problem

[AVTekk]

def drivetrain related. is it ext cab, std cab? whats the pinion angle set at?

[mister880]

sounds like your rear end..

[s10layinlow]

Reg Cab. Pinion at axel is +2 or 3, and from what I can tell at tranny its -2 or 3. The sound like I said CHANGES TONE as the FRONT bounces on highway. Im wondering if it has something to do with where the shaft meets the tranny? Or Wheel Bearing?

[dirttysouth]

Sounds like a bearing in the rearend to me

[railin93]

mine does the same thing and mine isn't bagged, just static right now...although it is bout a inch or so from the ground...i've been told that the factory driveshaft with the big donut-looking thing on the rearend is not a balanced shaft and the donut is a dampner for vibration and the donut wears out eventually causing the hum and eventual severe vibration...i was told by an ASE certified rearend specialist, that the only way to fully cure the problem is to change the rear yoke and get the shaft that is balanced...all hear-say for now but it's getting worse in mine as the months go by and i can tell it more now than before!

[Big_Bake]

mines ext cab and static and does the same humming/buzzing at highway speeds. only when on the gas if i let off it stops. i was thinking it was the u joints or carrier bearing cause it comes from right between the seats to the back of the cab. i figured i would replace them when i bag though.

[AVTekk]

sounds like the driveshaft is too long and pushing into the tranny. check to make sure its not jammed up in there, most std cabs need it to be shortened about 3/4".

as for big bake, its def your driveline, probably carrier bearing but also could be your driveline angles if youre dropped.

[s10layinlow]

Quote: Originally Posted by AVTekk

sounds like the driveshaft is too long and pushing into the tranny. check to make sure its not jammed up in there, most std cabs need it to be shortened about 3/4".

How could I find out if its too long? What kind of shop would I take it to? There are not any shops around here that do this.
Thanks

[AVTekk]

try taking the shaft out with the suspension fully compressed. if you cant, raise the truck up and take it out, then measure from the pinion to the tranny with the truck down, and compare it to the shaft. you want to have at least 1/2" of play between the two.

as for the shop, use www.whitepages.com to find one, and call around. try bigrig stores, they usually make shafts.

[s10layinlow]

How common is this problem? I have heard of having to notch the cab for standard cabs also, but mine seems fine. I will be doing this shortly. Thanks

[AVTekk]

Its very common.