Driveline Vibrations

[CharlesHS]

The 2001 Sport 4.0L that I purchased 14 months ago had OEM 20 year old sagging springs and decided to restore the factory ride height plus a little more.
The before ride height measuring from the floor to the fender flare on a level surface was 33.75” front and 35” rear and after 35.5”/37.25”. The springs are ProComp 2” which were economical and available; also replaced all four bump stops and the front rubber spring isolators.
Here is the interesting occurrence after the lift install; the Jeep is receiving driveline vibes, but after folding the rear seat down and and filling the gas tank the vibes are 85% gone.
I understand that the transfer of weight in the rear changes the driveshaft angles which reduces vibrations and could reduce a little more as the lift settles.
The suspension is stock other than Bilstein shocks.

Thoughts and opinions are welcome.

 

[Leroy_TJ]

I have the same thing , 2” Procomp springs. With a heavy swing out carrier and bumper I had no vibration. I took the swing off bumper and carrier off and installed a moryde tire carrier and now have vibration and a 1” rake back higher than front.

 

[Goatman]

You could put 1" engine mount lift or try adding a couple washers between the skidplate and frame to lower the transfer down a bit. Either 'should' work if a full tank is enough to smooth out the vibe.

 

[CharlesHS]

You could put try adding a couple washers between the skidplate and frame to lower the transfer down a bit.

I was having the same thought.

Thanks...

 

[Rubicon88]

Rear U joints

P.s.

Make sure you use Spicer

 

[CharlesHS]

Rear U joints

P.s.

Make sure you use Spicer

I have several Spicer 1310's in my parts cabinet.

Thanks.

 

[Rubicon88]

I have several Spicer 1310's in my parts cabinet.

Thanks.

 

[eastbloc]

and now have vibration and a 1” rake back higher than front.

Will add to this ^
My rear recently got higher than front, and i have been struggling to get rid of the vibrations. Half a turn on control arms shifts vibration point between lower speeds and higher speeds.
Switching to softer Rancho RS shocks has also widened height between highs and lows under load.

If few more + - in pinion angle or tire balancing does not do the trick, i will add spacer in the front to level the Jeep.

 

[CharlesHS]

Today I removed the transfercase skidplate bolts (clean bolts and chased threads) then check the bolt length and size for when I install the tcase drop spacers.
The bolts are 1/2"x13 NC and the threaded section is 1.125", but the bolt has a coned seating surface to mate with the recessed holes in the transfercase skidplate.
Does anyone know where to purchase similar bolts 2.0-2.5" long ?