Have the 2.5 rock krawler max travel lift on my 07 2 door JK and have Adams front and rear driveshafts. My kit includes adjustable front and rear lower control arms which are set to the spec lengths that rock krawler suggested. The first time I went out with my Adams shafts, I broke the rear shaft due to incorrect pinion angle when crawling a ledge. The great folks at Adams replaced my shaft for me, but I need to correct my pinion angle so it does not happen again.

I looked at pulling the control arms again and shortening the length and realized that I only have a very small margin (about 1/4" if that) to shorten the arms to gain more pinion. I understand that I may have to go with upper adjustable to correct this, but I have seen tons of people running the same lift on their 2 door with no issues. Has anyone else run into this problem? I'm trying not to spend the extra coin right now on the uppers and have a competition coming up that I will be competing in with my JK. Can anyone help?!

Here are a couple pictures of my angles (not the best pictures, but it will give you and idea....):

 

Nobody has run into this issue?!

 

Angle looks spot on to me. What do you think it should be?

 

How did the pinion angle cause a driveshaft to break while crawling a ledge? I would think that slamming it down on a rock ledge would suffice, regardless of the angle.

 

I thought it was close but according to Adams, it is not correct and is the reason why I broke it. This is what the angle is supposed to be, either 0 degrees or +1 at the axle.

 

Apparently when I was crawling the ledge and my rear coils were loaded, it caused too much of a negative pinion which caused the u joint to break and as the shaft spun, it broke the ear off of the flange. Here are some pics of the carnage:

 

You got a Hemi in that thing?

I can't see how being off 3 degrees when low-speed crawling can cause that kind of break. Slamming against a rock might do it.

If you have to be perfectly aligned, what's the point of a U-joint? Sure, because the other end is a double cardan that approximates a CV you don't get the velocity balance of having a single cardan at both ends but geeze... that shouldn't fall apart like that. If it was just the yoke or just the cross I would chalk it up to bad material but both? Was the U-joint ever over-heated or not greased (assuming not sealed)?

 

What gearing are you running with those 37's?

 

I agree, I thought the same but that's what it was determined by Adams on the failure. Regardless, they stood behind their product and took care if it for me. I'm just hoping this doesn't happen again which is the point of this thread. The shafts were completely greased, including the u-joints. I am anal about that....

 

4.10 but when I broke I was running my 33's.