Vibes revisited - Shackle?

XJack · Sep 30, 2004

Definitely an acceleration vibe - Noticeable at 45-48mph, worrysome at 60 mph. Let off the gas and it rolls like it's on glass. Pinion is 1 degree low with 2-degree shims.

The leaf packs are 18 months old or so with a decent amount of wheeling (and rust).

'99 XJ 4.0 AW4
RE 3.5" SF w/ HD springs
New D44 swap
New 1.25" Shackle
6" of even lift all around, *except* the driver's rear is 5.5".

Scratching my head here a little, and considering a transfer case drop to see what effects it will have on the geometry.

Can a shackle cause enough spring wrap to pull the pinion up this far?

JohnJohn · Sep 30, 2004

IMHO you need an SYE. Your vibe is coming from the driveshaft yoke moving back and forth on the t-case shaft.

XJack · Sep 30, 2004

Whoops! Forgot to put that in there. I am running an AA SYE and Spicer shaft.

Any other thoughts?

JohnJohn · Sep 30, 2004

XJack said:
Whoops! Forgot to put that in there. I am running an AA SYE and Spicer shaft.

Any other thoughts?

hmm, I see your degree measurements, 2*s seems like it wouldn't be enough. I guess that depends on if you welded perches on or are using the stock D44 perches.

Could it be your front shaft? The front shaft will spin on a 99. You might try pulling that off and seeing if the vibe continues. Your front pinion may be off.

BillR · Sep 30, 2004

JohnJohn said:
Could it be your front shaft? The front shaft will spin on a 99. You might try pulling that off and seeing if the vibe continues. Your front pinion may be off.

I think John hit it. That was sure my issue with the same vibes. I tried adjusting the pinion angle with adjustable UCAs, but there's a fine line between having a good pinion angle and having enough caster to track well down the freeway. I never found a happy point I could live with after the gear swap, as my driveshaft was spinning much faster with 4:88s. I ended up doing a hub conversion to eliminate the front shaft turning when it didn't need to. It was hella spendy, but it DID fix the vibe problem. You can also cut and rotate the knuckles if you have the tools or know someone.

XJack · Sep 30, 2004

I took off the front shaft, as I can only work on one set of vibes at a time. :dunce:

John, I'm using the stock D44 perches, but I've measured the sucker three times and the pinion is 1 degree low.

Gonna pull the shims out completely and measure, drive, measure, drive.

JohnJohn · Sep 30, 2004

XJack said:
I took off the front shaft, as I can only work on one set of vibes at a time. :dunce:

John, I'm using the stock D44 perches, but I've measured the sucker three times and the pinion is 1 degree low.

Gonna pull the shims out completely and measure, drive, measure, drive.

I would try 4* or 6* shims. Under power the leafs may be wraping up more than normal; since the leafs are 18months old.

JohnJohn · Sep 30, 2004

BillR said:
I think John hit it. That was sure my issue with the same vibes. I tried adjusting the pinion angle with adjustable UCAs, but there's a fine line between having a good pinion angle and having enough caster to track well down the freeway. I never found a happy point I could live with after the gear swap, as my driveshaft was spinning much faster with 4:88s. I ended up doing a hub conversion to eliminate the front shaft turning when it didn't need to. It was hella spendy, but it DID fix the vibe problem. You can also cut and rotate the knuckles if you have the tools or know someone.

same reason I did a hub converison. Zero castor rocks on my set up, but not with a spining shaft...so what do I do...through money at it and shut the garage door real fast so I don't have second thoughts.

Vibes revisited - Shackle?

XJack

NAXJA Forum User

JohnJohn

Member #42

XJack

NAXJA Forum User

JohnJohn

Member #42

BillR

Toy Jeep driver!

XJack

NAXJA Forum User

JohnJohn

Member #42

JohnJohn

Member #42

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