After running the Rubicon a few weeks back we noticed a scratching noise from under the passenger side of the jeep which only happens under the right set of circumstances. If we make a hard left with some speed we hear the noise. Found out that the t-case side of the rear driveshaft flange is making contact with the OEM Gas Tank skid. Apparently, we did some damage to the skid and seams popped apart and is close enough to make contact under those situations.

So here are some of my thoughts/questions:
How much Engine/t-case lateral movement should there be? Seems like even with the gas tank skid tearing open there has to be somewhere between 1/4-1/2" movement to make contact. Investigating the t-case mounts they look intact but I need to check the engine mounts. Is it possible one is broken? I would think it would be very noticable if an engine mount was broken, is that correct?

Questions for those who have been there done that:
How difficult is it to drop the gas tank skid? Also, how hard is it to either cut off the section that split apart or bend it back into shape and tack weld it back together. sounds straightforward am I missing anything? Seems like the biggest thing is that the plate thickness but I could be missing something.

My major questions are how much lateral movement is there with the engine under normal circumstances?
What symptoms are there for damaged or broken engine, transmission or t-case mounts?

Thanks for your help and advise!

 

There's a couple of things going on here. First off, I know you have taller coils now but not an adjustable rear track bar. Because of this, your axle will be off to the passenger side of your Jeep. The transmission and engine mounts are rubber and do allow for a considerable amount of movement. Being that your axle is off, it can and is most likely pulling everything over a bit and clearly, enough to make a difference in your specific conditions. Next, I see that you have a Coast driveshaft with the spacers - if you had a standard drive shaft with new yokes installed, you would not be having this problem at all as the yoke is much smaller and would be pulled way back to the T-case. What I would recommend is prying or hammering the skidplate flat again and installing an adjustable rear track bar to correct the position of your rear axle. That will take care of your problems and without having to drop your gas tank.

hope the call helped - let me know if you have any questions.

 

I'm going to check it out tonight and hope to get the skid that peeled away further away so there's more room for the lateral movement. Going forward the adjustable trackbar is probably needed as we've definitely moved up in height and never made the appropriate adjustments so rear is most likely shifted over a bit. Thanks again for the call and help!

 

Update:
While WOL was correct in his assessment that our rear end of the jeep was shifted over and since we didn't have an adjustment track bar it was shifted over so we got the TeraFlex rear Monster TB and it helped out but still didn't remove the problem.

So here's what I ened up doing.
We hit our oem skid in just the right place on the Rubicon Trail and it ended up breaking some of the spot welds holding a couple of pieces together.


The end result was interferance, during certain articulation conditions, with the driveshaft flange.


Unfortunately, the tight location didn't allow for it to be fixed. As you can see I attempted to cut out the section that was interfering but couldn't get the grinder up there.


So I decided to drop the gas tank/skid down so I could get at it.


That did the trick and I was able to cut the piece that was interfering away.


The end result turned out pretty good.