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big bang from rear?

K

kmagnuss_2000

NAXJA Forum User
Location
North Port, FL
Okay...I have a 99, 4.0, auto. I had about 6" of lift on it, but I couldn't stand the rough ride, so I took out the 2" spacers in front and removed the 2" short AAL from the back. So now I'm sittin at about 3.5" or so. Well, here's the problem. When I hit a bump...a sharp bump, like a crack in a road that sticks up a couple inches, there is a big loud thump/bang that I not only hear loud, but feel as well. It only happens on very quick bumps, not on big dips or anything. The shocks seem to be compressing fine, and I can jump up and down on the bumper and make the compress okay that way too. I have no idea what the problem is. Oh, my rear is lifted via a long spring from a 00 s10 zr2 and a RE extended greasable shackle. And I have Doestech dt300 shocks, with the can installed on top. Thanks for the help.

-Keith
 
axle u-bolts?? posible that they are too long now with the leaf removed, and are now hitting the body?? go back and re-torque EVERYTHING in the rear suspension...
 
Nah, it's not the shocks bottoming out. They are the same shocks I had from my 2" RE budget boost. And it doesn't look like the ubolts are hitting anything. Do you all think that the shocks could be going bad and maybe the valves are sticking or something? Should I try turning them around the right way?
 
Do you have a sye? Slip could be bottoming out. For that matter, if you havent, how much slip is showing in your slip yoke. that could be it too.
 
Is the driveshaft bottoming out?
Shackle angles, maybe hitting the rear of the unibody?
On a side note, with no other mods, I don't see how the same shocks working for a 2" lift and a 6" lift.
Not gonna happen.
HTH.
 
yeah, with 6" (actually, it was 6" in front and just over 5" in back) the shocks only had about 3" of travel left in them. I don't have a SYE. I do have a 1" TC drop. It almost feels like the driveshaft could be bottoming out. I think the pinion angle is wrong for one. It seems to be pointing up almost in the same line as my driveshaft. Maybe I'll try putting in my agle shims. Grrrr. The Shackles aren't hitting the body, or hitch.
 
With no SYE you need your t-case output shaft and your rear pinion at THE SAME ANGLE from the horizon.
With an SYE, you point the pinion at the t-case or close.
Without one, you need to keep the angles the same.
2joint_angle.gif

An angle finder will cost you $10 at ACE.
 
No SYE. I looked more closely at my rear pinion angle, and it's not as far off as I thought it was, but it could use some shims. (I'll try this weekend). I took out my 1" TC drop last night and it didn't help any. However, the vibes are barely noticeable, so I'm going to leave it like it is. But that stupid bang is still there. If anybody lives near me in FL that would like to go wheelin this weekend and check it out, I'm game. I have no idea what to try next. I almost feel like the shackles are not quite in the right angle and sort of bind when they go back and forth real quick. ????
 
Are the bolts at the top of the shocks tight? The bolts thru the bar pin.

Are the shackles hitting the bumper bolt that sticks out in front of the rear crossmember?


hinkley
 
I've had what sounds to be the same noise from the rear passenger side. The quick bounce was actually making the leafs catch on the muffler/tailpipe hanger and when it let go I heard the bang sound. Check to see if you can notice scrape marks along the exhaust pipe around the leaf area.
 
These are all good guesses fellas, and I really appreciate your help. Hopefully I can figure this thing out this weekend.

When I had my YJ with shocks that were WAY too short for the lift (we're talkin about an inch of travel left here before they topped out) it made a very similar sound/feeling. Hmmm....but these shocks have plenty of travel left.

I've had the shock mounts come a little loose before, and that was a lot quieter sound than this.

Thanks again guys. And gals?
 
Here's a really stupid idea. Why don't you run throught he process of elimination? Remove your rear shocks and go for a drive. I the sound is gone you need some new shocks. Otherwise you'll have to start changing other things.
 
I am an idiot. I took out the shocks. Uh, yeah. I had like two inches of travel left in the driver's side, and about 4 inches in the passenger side. Time to fix the pinion and get some new shocks. Thanks for your help guys.

-Keith
 
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