Rear suspension vibration

[MillerRacing]

I lowered my truck with a set of 2" rear shackels and they look great but has developed a slight vibration. It only vibrates from a start to about 10mph. It is not too noticeable but I know it is there. Do you guys know if you have to add a leaf spring wedge between the rear axle and leaf spring to correct pinion angle? Or do you think it might just be the U-joints do to running at that angle for so long?

Another question is that when I lowered it, I noticed that one axle bump stop was missing. So I went to ford and they discontinued them. Our local pick-n-pull just had they ones that are square. I was thinking about getting some shorter ones due to being lowered but does anyone have any ideas or have you run into this issue?

[SR81]

2" shouldn't bother your pinion angle. You may need to check the angle and shim the U joint. I just cut my bump stops down. Or you could go with Energy Suspension

[MillerRacing]

2" shouldn't bother your pinion angle. You may need to check the angle and shim the U joint. I just cut my bump stops down. Or you could go with Energy Suspension

What do you mean by shim the U-joint? Does anyone have a energy part# and are they shorter?

[SonicHD]

There are angled shims that go under the leaf to change the pinion angle. Usually not needed though for 2" shackles only. 4" drop or so, yeah for sure.

[MillerRacing]

Do you think it may just be the U-Joint?

[SR81]

Could be or the carrier bearing

[Harley#356]

it's pretty common to need to rotate the shim at the leaf spring pack to resolve any vibration issues with a 2" drop.

[MillerRacing]

Great, I'll spin that thing around and try that, Thanks

[MillerRacing]

Update, yall are great it fixed my vibration. I just spun those things around and wala fixed. Also put a set of energy suspension universal bump stops on too!!!

[3653 Owner]

anyone have any pics of how to do this???

[MillerRacing]

No, but I just put it on my lift and let the suspension hang, jacked up the rear end housing a little to remove the weight off the springs, then removed the axle u-bolts. Then I lowered the rear end housing enough to get to the leaf spring wedges. Then I took an air hammer and bumped them around 180 degrees. Then jacked up rear end to the springs, installed the u-bolts and lowered the truck back on the ground. Went for a test drive and no more vibration.

[SoCal Waite]

Jack up the rear of your truck with stands under the frame, then support the axle with a jack under the diff. Pull a wheel off one side, then remove the U-bolts that hold the axle to the spring. Slowly drop the jack till all pressure is released from the spring on that side, then go just a little further till you see light between the spring and axle perch. Then with a hammer and screw driver or punch tap one end of the shim until you spin it 180°. Then jack the axle back up (make sure the pin in the spring lines back up with the hole in the axle perch), put the U-bolts back on and tight. Then rinse and repeat on the other side.
Spring Shim.jpg

[Blind]

U bolts should be replaced anytime you remove them. They are torque to yield on every truck I've checked. Big safety risk to run around with stretched twice U bolts holding the rear end in place!

[3653 Owner]

Ahhh thank you very much for the pic, helps alot for us description challenged, LOL.

[SoCal Waite]

Crap, thanks Blind. Guess I'm going to have to go pick up 4 new U-bolts. I've looked around a little bit for that info, but never found a concrete answer. You by chance know the torque spec for them too?