drive line vibes from new springs?

I had my mechanic install a set of the heavy duty springs from Quadratic as well as a set of shocks in the back.

I also installed a TNT cross member with no t-case drop.

My rig sits a bit higher than it use to as my old springs were to the point of frowning from all the sag. After the install, I seem to get an occasional thunk noise when I take off from stop. And at high way speeds I seem to have a little more vibes in the rear than I use to.

Some of it I suspect is from the stiffer ride for the vibes, but the thunk has got me baffled. The only thing I can think of is that I have increased my drive angles and until my new springs settle in, I will have to much angle.

I grabbed my rear drive shaft and gave it a twist, but it felt solid. Could my u-joints be going and the increased angles are making it more noticible?



I have a pretty much stock '96 with 30 x 9.5 BFG TK/KO's that I have been running for the last 6 years. AX15 5 speed tranny and 8.25 Chry rear end. 81,000 miles on the beastie.

I have heard that u-joints can "settle" into a certain angle and sorta get used to it. Once you change that angle a little bit, they can act up and may need to be replaced.

I am not the one who said this, so I am only passing this info on to you.

Loose Ubolts can cause a klunk. Recheck the torque on the Ubolts, they need to be checked every week until they hold tight.

You have the newer slip yoke with the rubber boot, right? The slip yoke can thunk on acceleration and if you pull it apart and grease the splines it may stop making noise. Did the mechanic drop the rear driveshaft to do the springs? Did he get back in the same orientation?

Drive for a while and see if the new springs settle in and the noises get quieter.

Tim_MN said:

Did the mechanic drop the rear driveshaft to do the springs? Did he get back in the same orientation?

Click to expand...

Theres no such possibility with a factory rear shaft,it only applies to driveshafts that have a slip-yoke "between" the u-joints!

i had the same thing after i put them on my 2001 xj, but as the springs "break in" and settle it seemed to mostly go away.

i'm debating throwing a main leaf in or just using my mj shackles for 1" extra lift but with my heavy rear bumper and tire carrier, i'm not sure which would be best. i don't plan on lifting anytime soon, just want the room for my moabs so they don't rub if i have extra weight in the vehicle. with that little extra lift though, i think i'll have to add a t-case drop like the one that came from the dealer with the up-country package. maybe you need a small t-case drop, too...but i'd either check your u-joints, give a good greasing, or wait for them to settle. hope this helps...

The klunking I feel underneath is not repeatable. Only seems to happen when I startout from a dead stop, but not always. Seems to happen more if I am on an increasing incline, but again not repeatable. It feels as if someone is smacking my center console and makes it rattle as if I take my hand and smack the top of it.

The new springs are only 2 weeks old and still have plenty of lift to them. The ride seems to be improving the more I drive it.

Update.

After letting the beastie settle a little bit, the clunking has gone away. This to me indicates that it was an increase in the drive line angles causing it. I still have a little vibe in the rear when I get past 45, but I think it will improve.