Driveline Vibration after Geo Correction Brackets?

[JDK]

BLUF: Vibration after installation of JKS Geometry Correction Bracket.

I have a bit of a Franken lift on my ‘01 Willys consisting of Rubicon Springs/Shocks, 2in Teraflex spacers up front along with Mopar lower control arms and 1in Teraflex spacer out back for about a 2.5in/1in lift front to rear.

Wanting to improve steering feel, ride and address occasional DW I installed a set JKS Geometry Correction Brackets, and reinstalled the original lower control arms. I have the upper control arms in the top hole of the bracket.

Immediately upon test drive I could feel vibration at ~1800 RPM and ~2300 RPM regardless of speed.

I did not feel any driveline vibration before the geo brackets.

Could the geo brackets have induced driveline vibration with such a small lift? Would I feel higher NVH with the geo brackets?

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[professorkx]

Maybe. I would remove them as a test before I started chasing any other cause. No sense chasing ghosts…

 

[PuddleJumper]

remove the front driveshaft and see if the vibration is still there.

 

[InvertedLogic]

That's weird that it's RPM linked and not speed linked. If it was the ds vibrating it would be at specific speeds regardless of engine RPM.

 

[JTGuy]

Remember that the front DS does not spin unless it's in 4x4 mode. The JKS brackets really should not cause any driveline vibes. They will add about 2 deg of caster. just make sure it's not in 4x4 mode.

 

[JDK]

Remember that the front DS does not spin unless it's in 4x4 mode. The JKS brackets really should not cause any driveline vibes. They will add about 2 deg of caster. just make sure it's not in 4x4 mode.

That’s what I thought with the FAD, but I’m struggling to think what else is causing the hum and vibration. This morning I did put in to and out of 4WH a couple times just to see if that made any difference, but it was inconclusive at the speed I was moving.

I hadn’t driven the JT since Thursday when I returned from a business trip, approximately 4hr drive, until Sunday night other than to shuffle it around the driveway.

I don’t see how or why an alignment would be necessary with the geo brackets. I do need to recenter my steering wheel which is just slightly turned to the left.

Tire pressure is around 33-34 on year old 315 Goodyears.

Hit speeds of 60-65 on the way to work this morning. I feel the vibration at 1800RPM, nearly nothing at 2000RPM, and then again at 2300RPM, regardless of gear I’m in. At a steady clip of 60mph in 8th it’s turning ~1800RPM, I feel the vibration. Bump it into 7th, I hit 2000RPM annd maintain speed and the vibration disappears. Accel up to 2300 RPM, regardless of gear, the vibration returns and feels more harsh at the revs climb until the auto down shifts back to the 2000RPM range.

 

[JDK]

Welp, I had everything inspected by a reputable shop. They told me they didn’t see how the geo brackets would cause drive line vibes. Suggested it might we the 1st signs of rear axle bearings failing. They did find a couple of bad tie rods. They re-torque on everything and found loose knuckle nuts (My wife hates when that happens).

Drove home, still feeling the vibes. Once home I installed a RockJock carrier bearing spacer. This eliminated 99.9% of the vibes.

 

[JDK]

Welp, I thought the carrier bearing drop was the solution. Jeep is now replacing the rear axle under warranty. I don’t know the exact prognosis on the axle. The axle was serviced, drain and fills, etc. only towed a flat trailer a couple times hauling yard debris. Nothing that stressed the Jeep.

 

[JDK]

Took about two months to receive a replacement axle.

This did not fix my driveline vibe issue. To add to the insult, I now have a clicking/knocking noise when making left turns under throttle. Had the front u-joints inspected by a reputable shop, they say the u-joints are fine.

Had all four wheels rebalanced, and there was a noticeable improvement in feel at highway speeds, but it had zero impact on the vibrations.

I now associate the vibration with 1500rpm and 2500rpm, regardless of speed or gear.

 

[azmojave]

That’s weird. I have JKS brackets but don’t have any issues. Hard to believe that’s the cause but who knows

 

[JDK]

Checking everything again with the drop brackets. Completely missed that the driver side exhaust loop is touching the drop bracket. Loosened the exhaust flange bolts on either side of the y-pipe and was able to gain about an 1/8in of gap. Still too close so still rattles in some situations, but definitely improved.

But to add insult to all of this, I broke one of the flange bolts.

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