donkengine

I just installed dorman 929-301 heavy duty leaf springs and have a new vibration from 30-40mph. Height from center of wheel to bottom of fender flare is 18.5".

What should I do next?
-let it vibrate and hope it settles
-new u joints
-shim axle
-t case drop
-sye

Will ZJ v8 front springs level it out?

Quick review on the springs: Very well made and include bushings and the friction pads. They ride great with no new squeaks etc.
As for the install, all of the factory bolts had red loctite on them. You must heat the nuts with a torch before removing. The front bolt has to be heated from inside the frame rail. There is an opening in the perfect spot to do it. Blow everything out with air first and have at it. Kroil everything as well.

Fred/N0AZZ

I take it you were not wanting any lift or you would have bought a kit, correct? If you had wanted a lift you should bought parts to match the cost is about the same and then you can pick better quality leafs/coils to match as well as shocks.


More information is needed for a better reply.

donkengine

I did not want a lift. I just wanted to fix the sag and be able to tow a small trailer.

donkengine

Anyone? Bueller?

Did I post in the wrong forum? With the trailer and about 75lbs in the rear the vibrations went away.

BNJeepsta

The problem is the small amount of lift you gained is causing driveline vibes. Leveling it out, likely, will not fix the issue. You could either drop the t-case a little or load the rear nice and heavy for a while to help the leaf springs settle quickly.

donkengine

Leveling is a cosmetic desire only. My main goal is to cure the vibrations. I haven't measured angles yet but it looks like my pinion angle is a bit high. I can't believe a 1" lift is enough to throw it off.

U joints have 110K on them so they might be due for replacement as well.

abodyjoe

i'm wondering if the u-joints are bad. they could have worn into the previous angle. worth a try. have seen stranger things over the years..

md21722

You've altered the ride height and the u-joints were worn into the old height. If you give it a few weeks it will probably go away. If not, change the u-joints.

This happened to me last year when I replaced the sagging springs with Dorman 929-301 and the problem went away before I changed the u-joints.

donkengine

Thanks! I realized I had tightened the shackle bolts before putting the wheels back on so this afternoon I loosened them and sure enough they were slightly bound. I bounced the back a couple of times with the bolts loose and tightened back up. I had the trailer and family in it after that so I couldn't tell if that did the trick.

I am loving how much better it rides and handles with the new springs. The stock ones were slightly sagging but apparently were much weaker than I realized.

kgm

If you don't know how old the u joints are, I'd just replace them. It's $40 for the pair and should quiet it down as well. Lube the slip yoke while you're at it!