Hey guys, got a question about my personal vehicle. It's a '00 extended cab swb 4.6L with 4r70w trans. I have a Hotchkis TVS 2/4 kit on it. It's been lowered 3 years now and I've never had any real issue. But I started noticing a small vibration through the floor so I took my driveshaft out to be balanced and new U joints installed. Ever since then I've had an audible "hum" from the rear whenever I go over 75mph. It only does this under load (hill, etc) and I don't hear anything until then. The driveline shop told me it was my pinion angle and I've tried shims with only slight improvement. Has anyone run into this before? I'll replace the driveshaft after I do a motor and trans swap down the line, but it's out of the budget for now. Any help would be greatly appreciated!

Andrew

 

maybe when you under a load it straightens out the pinion angle to being straight and thats were the hum comes from. how straight is the angle? it has to be angled from what i know. also have you checked your diff fluid?

 

It's angled slightly down right now. I've been trying different shims, started with a 4 degree and now have a 2 degree. I want to drop it down to a 1 degree and see what that does. Diff fluid level is good and changed less than 10k miles ago. I guess the biggest thing is none of this started until after the driveshaft was balanced and new u joints (non-greasable) were installed. It's just got me

 

hmmm...maybe the u joint was not made correctly? or take it to see of its balanced again. they could have messed up onsomething

 

I noticed my stock height 02 4x4's rearend humming about 3 years ago on big hills; when i first started driving the truck. I think it's fairly normal unless the noise is excessive, mine is never really noticeable over the exhaust or radio. My rear end now has 199k miles on it.

 

mine has never hummed...i actually think it may be your back lash in your rear end.

http://www.therangerstation.com/tech...g_backlash.htm

 

i have an 02 f150lifted and mine has never hummed. but a tiny clunk every now and then

 

Yeah, I was starting to wonder if it's a bad out of the box U-joint. I've got a speed shop near me that I trust. I actually had them rebuild the rearend a few years ago. Thanks for the input guys. Don't forget to give me a call and let me know you're from the forum and I'll work deals for you.