2005 Rubicon Rear Differential Rubbing Fuel Tank

Alfman45

Alfman45

New Member
Joined
Aug 19, 2018
Messages
14
Location
Jersey City, NJ
Just purchased this Rubi with what seems to be a Rough Country 2.5” X-series(??) lift with 33’s on 15” wheels. I noticed straight away the rear diff rubbing (more like hitting) the gas tank shield.

My observations:
- the adjustable control arms seem to be “unwound” a good amount for a 2.5” lift
- rear tires sit a touch rearward in the wheelwell.
- no body or frame damage.

Seems the lift was installed incorrectly, guessing installed in the wrong order? Any guidance on diagnosing would be appreciated. Sorry my pictures suck.
 
Those images don't work. Download them and upload them from your computer using the "Upload a File" button next to the "Post Reply" button.

Your issue is no doubt due to the fact that the control arms are way off in adjustment. Someone likely tried to extend the wheelbase but didn't consider that in doing so they reduced the clearance between the rear diff and the fuel tank.

Still, I need those pictures to work in order to know for sure.
 
  • Like
Reactions: 05 Blue Unlimited
Here are the awful pictures

IMG_4814.JPG


IMG_4813.JPG


IMG_4811.JPG


IMG_4810.JPG


IMG_4791.JPG
 
This right here:

IMG_4791.JPG


All it took was one second of looking at that photo to know that your rear wheel is pushed WAY to far back in the wheel well!

So your issue is that someone has extended your rear control arms much, much too far... I'm talking inches too far!

This is why your rear differential is contacting your fuel tank.

My guess is that someone tried to extend the rear wheel base without thinking about what the result of that would be in terms of clearances.
 
  • Like
Reactions: jjvw and billiebob
Thanks for the quick diagnostic Chris - What would be the steps you would take to fix? (Complete reinstall, remove control arms and adjust, etc)
 
Wheelbase is set too long. As the rear compresses, it moves rearward some which is causing the interference with the tank. At 2.5" of lift the stock control arm lengths are fine. I would try and find the stock lengths and adjust the CA's to that for a start.

Not sure what shocks those are but they look to be too long for the lift.
 
When correcting the wheelbase after the bump stops are extended (as is typical with a suspension lift), the rear wheels ought to be centered in the wheel opening when at full bump.

Many will center the wheels at ride height or try to extend the wheel base by lengthening the control arms. Neither is the correct way.
 
From prior experience, the RC X-factor control arms are a ticking time bomb. If you can swing the cost, I would replace the shocks and control arms asap. The springs in that lift are most likely the only thing worth keeping.
 
Alfman45 said:
Thanks for the quick diagnostic Chris - What would be the steps you would take to fix? (Complete reinstall, remove control arms and adjust, etc)
Click to expand...

At 2.5" of lift, your control arms should be stock length. So yeah, basically you just want to adjust them back to stock length, and keep the pinion angle in mind, assuming it has a CV driveshaft and SYE combo.
 
Chris said:
At 2.5" of lift, your control arms should be stock length. So yeah, basically you just want to adjust them back to stock length, and keep the pinion angle in mind, assuming it has a CV driveshaft and SYE combo.
Click to expand...
If the arms are adjustable and the bumps have been extended and the pinion is no longer in the optimal position after a spring lift, then there is no reason to simply stay at the stock control arm lengths. Adjust and make the most of what you have available.
 
jjvw said:
If the arms are adjustable and the bumps have been extended and the pinion is no longer in the optimal position after a spring lift, then there is no reason to stay at the stock control arm lengths. Adjust and make the most of what you have available.
Click to expand...

I should have been more specific. I meant to suggest that the lower arms will more than likely be at the stock length. The uppers would of course need to be adjusted for the pinion angle.

In my experience with my old 2.5" OME lift, the control arm lengths barely changed from stock (the lowers were identical in length)... at least at 2.5".
 
Alfman45 said:
I’m sure this is somewhere on the forum but what is the correct pinion angle for the rubicon?
Click to expand...
We need more information. Regardless, the correct pinion angle is the one that puts the u joints within their working range of motion at the Jeep's normal ride height.
 
My .02 which just a thought that a expert can chime in on.....

Does it still have a slip yoke? It looks like it’s too far back for a slip yoke to reach so you may not have one. If the slip yoke was eliminated they may have measured wrong trying to do a hack n tap yoke (or didn’t cut the output shaft at all) and pushed the axles/pinion back trying to compensate....in that case you probably can’t move it forward because the driveshaft is all fixed length with no slip. Then you would need to remove the driveshaft, get the axle where you want it, and redo the sye for the correct length.
 
Xposure said:
My .02 which just a thought that a expert can chime in on.....

Does it still have a slip yoke? It looks like it’s too far back for a slip yoke to reach so you may not have one. If the slip yoke was eliminated they may have measured wrong trying to do a hack n tap yoke (or didn’t cut the output shaft at all) and pushed the axles/pinion back trying to compensate....in that case you probably can’t move it forward because the driveshaft is all fixed length with no slip. Then you would need to remove the driveshaft, get the axle where you want it, and redo the sye for the correct length.
Click to expand...

The Rubicon doesn't have a slip yoke to eliminate. The slip is in the shaft.
 
  • Like
Reactions: Xposure
How do I verify the Rough Country lift that I have - I assumed it’s 2.5” X, but I dont really know? Can anyone tell from eyeballing the pictures?
 
Measure the springs at ride height, not including the factory spring isolator. Stock springs measure 12" front, 8" rear. Anything over that is your lift height.
 
Top Bottom
Back