Vibrations and the Ideal pinion angle
 

My XJ has 5" lift, an SYE a custom shaft and run 32's. Before I installed the SYE I used a 1" T-Case drop to compensate and I did not have any, or very minimal vibes. Wanting to do it right, I put in the SYE and removed the TC Drop - since then my vibrations increased around the 45mph mark and up and are now just annoying. My pinion angle and DS angle are both 15 degrees.
Any thoughts on this? Should I put the TC Drop back in? Possibly shims? Looking for ideas.

Thanks in advance.

What are yoiu running for a driveshaft?

If an SYE was installed .... he must have a double carden / CV joint. Brand or style should not matter here.



Your pinion angle should be about 2° less than your driveshaft angle. That way .. and the spring flexes ... everything will be inline. Right now ... as you drive, you are actually forcing the pinion to have MORE angle than the driveshaft as the spring moves.


Basically ... you want to find a 2, 2.5, or 3 degree shim and insert it so that you pinion angle is less than your driveshaft angle.


Do that ... and your vibes should drop quite a bit.



Joe

Joe

He didn't mention what he has for a drive shaft. That is why I asked. I take nothing for granted here. He may not have a CV shaft, then again he might.

How would he not have a CV shaft with an SYE ?


Granted ... it CAN be made with a custom driveshaft .... but I highly doubt any driveshaft shop would make that for him.


I guess if he went and got some flange driveshaft assembly off a Jaguar or something. ;)


Otherwise ... I'm going to very safely assume it's either a yoke style CV shaft or a flange style CV shaft.


If I'm wrong and it bites me in the azz ... I'll find a way to get you a 6 pack. :D



Joe

Thank you very much for the input everbody. Yes I have a double cardan / cv drive shaft from Tom Woods, mated to the Chrysler rear.
I also have 1" rear shackles and an add a leaf with blocks. Would adding shims under the blocks be acceptable as far as safety goes? Would adding more between the rear springs and the axle contribute to increased axle wrap?

Well Joe, you are safe. You don't owe me a six pack. (soda pop cause I don't drink) But seriously though, I like to get all the info I can because many times on these forums we get all involved in going with a certain solution and find out later that there was some piece of information left out that was critical. In this instance, I was getting the impression that it might have worked BEFORE he dropped his tcase. That is why I asked the question. If it had, well it could have been that he did not have a CV

Steve

Steve ... I'm hardly faulting you for going the extra mile and getting all the info. I am just fortunate enough to have driveshaft catalogs here, that I know what parts are available to make a functioning shaft. Only reason I stuck my neck out so far. :devil:


xjjep ... in terms of spring wrap, it really won't matter where you put the shim. But in terms of a proper installation, the shim should be under the block (on the leaf spring perch). Pesonally, I am not a fan of blocks, so I don't have an "good" suggestions (other than to chuck them).


I would say to start with shims (they aren't going to be that thick) and see what you need. If you insist on running blocks, a few companies make tapered blocks to eliminate a few loose pieces. You can always buy or make a taller spring perch for complete adjustability.



Joe

Joe. I used to work for a guy that had a 4X4 shop and made drivelines. He was also Spicer/Dana direct and you would not believe what came out of that shop. All good stuff, but I am aware that there are some endless combinations that can be made. So with that background, I trust no one when they do their own stuff because some of it can be amusing.

Steve

The previous owner had the rear springs set up this way, and I felt the Jeep as a whole was a good base to work with. I personally would have gone with the full lift springs and no block, but it is what it is until if and when I replace the springs.
Thanks again for everyones suggestions.

Chris

Amusing huh ? I would probably use a stronger word.


But I'm with ya on that. :icon_lol:



Joe