- Joined
- Mar 20, 2005
- Location
- Hendersonville, NC
Going way back.
A few years back I lifted my wife's ZJ with a Rusty's 3.5" kit (all 8 arms, TB, etc), swapped in a 44 rear, regeared and added lockers. All in the same weekend. Pretty major change all the way around.
Started getting some weird vibrations/resonances immediately. 52-62 mph the rear view mirror would vibrate and a strange harmonic in the seat/floor.
Installed hack and tap SYE, different CV driveshafts, swapped in a 231 with a real SYE, etc and the vibe/resonance would change, but reappear. Total pain in the butt. Moved pinion angle grossly low, then high, no significant difference. So it wasn't an angle issue.
Did install a heavy wall, large diameter rear shaft from Tom Woods and it helped a bit. But eventually, came back. Told my wife essentially, deal with it. Lifted, locked unibody Jeep stuff.
Anyway, fast forward to last week and I'm installing all new control arms and track bars that Ironman4x4 sent me to do some R and D on for them. I pulled the old rear lowers and hardware out and set them on my bench to mock up the ones. Grabbed the bolts and noticed they were loose in the bushings... The ones on the frame end of the LCA.
2 of the rear OEM appearing LCA bolts were 0.490" diameter and 2 were 0.540". Identical heads, color, coating, grade stamping and nuts.
I have no idea where their actual application is (never seen that metric size on a Jeep) but they were on it when we bought it used, stock back in 14.
Anyway, installed proper 9/16" hardware, set pinion angle back to 13* and test drove.
50 miles of driving and zero issues anymore.
I suspect under certain conditions the smaller diameter rear LCA bolts were causing the LCA to oscillate on the chassis.
Regardless of my theory, it's finally fixed and even got the wifey's stamp of approval.
A few years back I lifted my wife's ZJ with a Rusty's 3.5" kit (all 8 arms, TB, etc), swapped in a 44 rear, regeared and added lockers. All in the same weekend. Pretty major change all the way around.
Started getting some weird vibrations/resonances immediately. 52-62 mph the rear view mirror would vibrate and a strange harmonic in the seat/floor.
Installed hack and tap SYE, different CV driveshafts, swapped in a 231 with a real SYE, etc and the vibe/resonance would change, but reappear. Total pain in the butt. Moved pinion angle grossly low, then high, no significant difference. So it wasn't an angle issue.
Did install a heavy wall, large diameter rear shaft from Tom Woods and it helped a bit. But eventually, came back. Told my wife essentially, deal with it. Lifted, locked unibody Jeep stuff.
Anyway, fast forward to last week and I'm installing all new control arms and track bars that Ironman4x4 sent me to do some R and D on for them. I pulled the old rear lowers and hardware out and set them on my bench to mock up the ones. Grabbed the bolts and noticed they were loose in the bushings... The ones on the frame end of the LCA.
2 of the rear OEM appearing LCA bolts were 0.490" diameter and 2 were 0.540". Identical heads, color, coating, grade stamping and nuts.
I have no idea where their actual application is (never seen that metric size on a Jeep) but they were on it when we bought it used, stock back in 14.
Anyway, installed proper 9/16" hardware, set pinion angle back to 13* and test drove.
50 miles of driving and zero issues anymore.
I suspect under certain conditions the smaller diameter rear LCA bolts were causing the LCA to oscillate on the chassis.
Regardless of my theory, it's finally fixed and even got the wifey's stamp of approval.
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