Driveline vibration

[DWC]

Hoping the collective wisdom here may be able help me out.

My daily driver is an 05' Silverado SB. Wanting to improve it's "attitude" I installed a McGaughy's 4-6 drop kit. Spindles, FR springs, RR flip kit. Ever since the install I've got a vibration/shake coming from the RR that I can't seem to fix. I swear you can feel it just going down my driveway but it gets progressively worse all the way to 50-60 MPH. It seems to come from the rear and move to the front then back to the rear. In sort of a wave if that makes sense.

Fixes I've tried so far:

Swapped the current rear tires for the rears from my Burb, they bolt up but look weird. Not much better, the Burb has much newer tires so that may be the difference.

Checked the pinion angle. Installed a 2 deg. shim in the rear, it is now +5 deg and the engine/trans is -4/5 deg. They are within a degree of each other so this should be OK, right?

Loosened and re-tightened everything I touched with a wrench.

In the half dozen trucks I've lowered I've never had something as frustrating as this vibration.

Any advice, opinions, past experience, anything would be appreciated.

BTW, it does look much better....

[DA68]

With a 6" drop, a shim may not be enough to correct the pinion angle. I know the Belltech kits for '99 - '07, used to recommend or include a bracket that lowered the carrier bearing, to correct the pinion angle. I would give the mfr. tech line a call or see what the competitors offer or recommend with their kits.

[87chevy.com]

do you have a 2pc drive shaft or 1 pc? if you have a 2pc, maybe the center support bearing is binding a bit. if you have a 1pc, maybe the balancing weight fell off or got knocked off... could happen on a 2pc too. Really sounds like its in the drive line if it gets worse with mph rather than rpm. All else fails, take it to discount tire and have em balance the tires... its always annoying to say, ah, thats not the problem... spend time on diagnosing and come to find out the simple thing was the problem...
clint

[DA68]

I failed to mention that these year trucks with two piece drive shafts are prone to vibration at stock height. Just Google "Silverado with vibration" and you'll find all kinds of blog sites, with owners having vibrations at stock height! Mine is at stock height and has always had a vibration at 70mph, with two different sets of tires, a new carrier bearing and new u-joints.
If you do have a two piece drive shaft and have or ever change the u - joints, it is imperative that you keep the orientation/relation of the shafts the same or you can introduce a vibration. I've read where several owners did not and had to have their shaft balanced. Hope this helps.

[DWC]

Hey guys, thanks for the response.

My truck has a 1 piece driveshaft, no carrier bearing, but I did try rotating it 180 degrees with no real difference. I'm thinking that taking it to a tire dealer for a re-balance is worth a try. Also will check into having the driveshaft balanced. I just wanted to be sure it wasn't something real obvious I was overlooking. This thing is driving me nuts.

I'll keep you posted on what I find out.

Thanks again for all the help.

[cdowns]

have you checked that the front yoke isnt bottoming inside the tranny?

[LEEVON]

I feel your pain, my last two lowered DD's have been just like that. 50-60 mph is almost certainly the driveshaft. It gets frustrating when the angles are good too. My 2008 has adjustable angle in the flip kit and I've hit it in 1 degree increments all the way from -6 to +6 with only slight improvements.

I'm sure you wouldn't do this but I was in a hurry once and tightened the axle down to the leaf springs and managed not to drop it in the alignment pin/hole. I drove around like that for probably a week, with the rear end skewed and it had a slight vibration.

Also, not sure about the '05 model but on the later trucks there are star washers on the brake drum (just to hold them on at the factory) that can cause vibrations with non-factory wheels. They have to be removed to allow the machined surface to sit flush on the drum.