Getting up to highway speed without shaking apart (05 LJ)

RexTreks

RexTreks

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Hey All!

I recently bought my first Wrangler, a 2005 LJ, and I'm working on getting some of the kinks worked out from the previous owner.

My first couple of projects involved upgrading to the ZJ steering components, getting it aligned, and replacing the track bar and dampener to try and get rid of some god awful creaking when turning the steering wheel. Now, with that all resolved and everything looking like it was in good shape, I got myself some new wheels, got them balanced, but much to my dismay, I can't get the truck over 65 miles an hour without it shaking itself apart.

From what I've read and seen, I'm having trouble discerning the root cause. I don't feel it much in the steering wheel, more in the feet, and there are differences between vibration on and off acceleration. The truck has a 4" Pro Comp (K3083B) lift that I I've been working on replacing components on as well; I have removed the drop track bar mount and returned it to stock, and then replaced all four shocks with Ranchos. I originally greased the OEM bolt that holds the track bar in place but I have a replacement ready to drop in next time I get under the truck. My ball joints appear to be in good shape, unmoving in North/South and East/West wiggletesting. Finally I aligned the truck using the bar method with an 1/8th" toe in per recommendations I have here on this site.

Where would you look next? Perhaps the driveshafts / differentials?
Since this is a 4" lift from the previous owner I'm not sure if care was taken to ensure correct pinion angles.

photo_2023-11-07_14-30-49.jpg
 
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Could be a driveshaft issue.
You can disconnect the front (at the pinion) to help determine which end the vibe is coming from.
How old are the tires?
What's the air pressure?
 
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LONGJP2 said:
Could be a driveshaft issue.
You can disconnect the front to help determine which end the vibe is coming from.
How old are the tires?
What's the air pressure?
Click to expand...

Throttle dependency to me indicates that its either axle positioning or driveshaft, not positive though, I'm fresh to jeeptown.

Tire age is under five years.
Air pressure is 33 on all four corners.
 
RexTreks said:
Throttle dependency to me indicates that its either axle positioning or driveshaft, not positive though, I'm fresh to jeeptown.

Tire age is under five years.
Air pressure is 33 on all four corners.
Click to expand...

Try lowering the air pressure.
Most run 35s around 26.
 
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One thing that might be getting me here as well is that the aftermarket lower control arms from the lift might just generally suck / have worn out. They are a box tube construction and are non adjustable. It's possible that since the track bar from the same lift failed (was very loud, creaky) that these components have similarly failed?

I'll have to make my next night under the truck pulling those off and inspecting for damage. Or.... I could measure the pinion angle, get adjustable arms, install them and set it to the right angle and call it a day?

What pinion angle range is acceptable for an auto LJ (non-rubi) with a 4" lift?
 
How do all the joints look while doing the dry steering test? If you put the driver‘s tire up on a ramp ant move the wheel, it the front still, or does it move with the wheel? It could be tires out of balance, or wheels bent/out of round too.
 
Artsifrtsi said:
How do all the joints look while doing the dry steering test? If you put the driver‘s tire up on a ramp ant move the wheel, it the front still, or does it move with the wheel? It could be tires out of balance, or wheels bent/out of round too.
Click to expand...

I'll give that a test with all the new hardware in place. I haven't tested that since installing.

As for the wheels and tires, I've had them balanced twice in the last month making sure that isn't the problem, so it's something else it seems. I suppose it could be the tires but Im leaning towards something funky with the lift
 
Pictures of your driveshaft rear and front. I'm thinking they did a lift without a DC shaft or didn't lower the skid. Pictures would help everyone here. Good luck Buddy!
 
RexTreks said:
I'll give that a test with all the new hardware in place. I haven't tested that since installing.

As for the wheels and tires, I've had them balanced twice in the last month making sure that isn't the problem, so it's something else it seems. I suppose it could be the tires but Im leaning towards something funky with the lift
Click to expand...

Balancing won't fix wheels that don't run true or tires with a bulge. Watch them while spinning on jack stands and you will see if one or more is bad.

To check driveshafts affect on the vibration,pull one at a time and drive it

A bent axle flange will also make it wobble
 
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RexTreks said:
One thing that might be getting me here as well is that the aftermarket lower control arms from the lift might just generally suck / have worn out. They are a box tube construction and are non adjustable. It's possible that since the track bar from the same lift failed (was very loud, creaky) that these components have similarly failed?

I'll have to make my next night under the truck pulling those off and inspecting for damage. Or.... I could measure the pinion angle, get adjustable arms, install them and set it to the right angle and call it a day?

What pinion angle range is acceptable for an auto LJ (non-rubi) with a 4" lift?
Click to expand...

I would double check the alignment of the bed with the cab of your truck. if their not aligned correctly the aerodynamics will cause your truck to shake ! you can also see if lowering your tailgate helps when reaching high speeds.
 
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