Rubicon Owners Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
1,414 Posts
Discussion Starter #1
I have enjoyed reading all the posts below regarding vibes, angles, double cardans etc. You guys are very informative!!

Your input on my next step would be really appreciated.

To date, I have an auto Rubi w/ a 1"BL, a 2.5" spring spacer, discos, adj track bar in front, Bilstein 5100's, nth degree skid.

The skid created vibes from 5 to 40 mph.

I would like to hold off on futher lift for a couple of years as it is my daily driver. But, this is the basis of my quandry...do I jump in now, or can I wait until I'm ready to use this jeep more off road than on?

The current pinion angle is about half way between where is should be for the stock drive shaft and a double cardan.

Can I set the correct angle with just upper controll arms? ( I feel like I've created the ultimate domino effect...) Or have I crossed the line and now need to get lower arms also? (which means to me that I should have just done the full lift in the first place)

Could I just add a double cardan & no control arms?

Based on your posts, I was planning to buy upper control arms and the Tom Woods double cardan. If I do that, should I set the pinion angle first and then measure the shaft? Or does that even matter?

The last paragraph contains my main questions. But....what other issues have I or will I create/mess up, etc.??????

Thanks in advance, Nick
 

·
Premium Member
Joined
·
2,772 Posts
You may be able to get rid of your vibes by adding a 1" MML - this will reduce the yoke to pinion angle as well as both of these to the driveshaft angle.

If that doesn't work, you can use the adjustable upper control arms to try and adjust the remaining vibrations out while still using your stock driveshaft. The transfer case yoke and differential pinion are aligned to be in a parallel plane by adjusting the upper rear control arms while monitoring each angle by using a protractor mated to the u-joint face, with a socket placed in between to keep good physical contact, for he yoke first, then rotate 90 degrees and measure the pinion.

Once these measurements look good, take it out for a test drive and see if vibrations occur during acceleration, decelleration, or not at all. For acceleration vibrations, shorten the CA's. For decelleration vibrations, lengthen the CA's.

If none of this works, time for a CV, and since I don't have one, I will defer the proper way to measure and buy.

Good luck,

Ken
 

·
Registered
Joined
·
85 Posts
If you buy a CV shaft now, you pretty much have to purchase upper adjustable control arms in the rear. This is because a CV style driveshaft dictates that you must have the rear diff pointing directly at the transfer case (i.e. only zero or 1 degree angle at the pumpkin). A stock non-cv driveshaft is setup so that the angle of the driveshaft relative to the diff more or less equals the angle of the driveshaft relative to the transfer case.

...and that's not the end of it. Once you angle your diff to accomodate the new CV shaft, you may have to repostion your rear shock mounts at the axle- this is because the shock cannister may interfere with the coil perch. You also may have rear trackbar interference or bind as well, again due to the rotation of the rear diff. Once you rear shocks are relocated, you now may have length issues, depending on the shock (i.e. they may bottom out before reaching full compression of the rear axle against the bumpstops).
 

·
Registered
Joined
·
556 Posts
When I raised my skid I had to knock out the forward knock out on the upper rear control arms. Once they were out the diff didnt move. So I mannually tried. Once the arms moved the diff pointet at the Tcase. It did help my vibes but sccording to your descriptions the diff should be pointing more towards the ground than the Tcase, right??? If so what harm am I doing right now having the stock shaft at a CV-like angle??? I am afraid that if I try to push the diff down toward the ground that the vibes will come back!!! I am taking a 7 hour drive next weekend and I'd like to know if my setup will cause me BIG problems. Please advise!
 

·
Premium Member
Joined
·
2,772 Posts
When you lengthen your Upper CA's, you are pointing the differential closer towards the yoke, so if this helps, you are moving in the right direction.

Ultimately, excessive vibrations will cause u-joint, bearing and seal failures if they are left unchecked. So, if moving more towards the yoke helps, then that is the way I would go.

My suggestions are after you test drive and determine whether the vibrations get worse during acceleration or decelleration. You follow these only if the vibrations get worse.

If the vibrations are the same for either condition, then they could be caused by the alignment, something loose, or an unbalanced tire.

Good luck and post some details of what you've tried and maybe one of us can help you eliminate them.

Ken
 

·
Registered
Joined
·
1,414 Posts
Discussion Starter #6
Thanks for the thoughts fellows.

Based on everything that I have read so far, (on this and the other threads) I'm going to try the Tom Woods double cardan first. (unless someone is adamant that I have no chance to solve the vibes without the control arms. This seems to be the next logical step.

When I do add control arms, can I just add the uppers? Or will this cause more issues? Anyone try just uppers?

Nick
 

·
Premium Member
Joined
·
2,772 Posts
All you need to start are adjustable rear upper CA's and rear shock relocators since you are going the CV route.

If you have trouble getting Caster back somewhere near specification when getting an alignment, you can opt for upper fronts, or lower fronts to to bring this back to 7 degrees +/- 1 degree. Most people go with adjustable front lowers. Good luck and have fun!

Ken
 

·
Registered
Joined
·
1,414 Posts
Discussion Starter #8
Woodie added! I'll find out soon enough if I "did good" or not. I also added the JKS UCA's. Everything was pretty easy except getting the front UCA bolt out of the passanger side. (had to man-handle the muffler a bit..no harm, no foul)

Everything runs fine but, a little of the old harmonic stuff is back at a higher speed than before. I used to hear the pulse at around 60-65 when the OD was accidentally left off. Now it shows up around 70 with it on, but not at lower speeds. Seems strange to me. The only other change made was the nth degree skid...which started the whole new drive shaft- adjustable contol arm-what's next.....process. Any ideas???

Also, the shock cans are very close to the springs and the track bar is against the gas skid. (which you all knew would happen) Is there any chance that the track bar and skid will work thier space "issues" out by themselves? Or, am I just going to break something? It seems to drive fine like it is.

Thanks again for the previous advice and in advance for any new thoughts,
Nick
 

·
Registered
Joined
·
1,530 Posts
badmonkeytoo said:
Woodie added! I'll find out soon enough if I "did good" or not. I also added the JKS UCA's. Everything was pretty easy except getting the front UCA bolt out of the passanger side. (had to man-handle the muffler a bit..no harm, no foul)

Everything runs fine but, a little of the old harmonic stuff is back at a higher speed than before. I used to hear the pulse at around 60-65 when the OD was accidentally left off. Now it shows up around 70 with it on, but not at lower speeds. Seems strange to me. The only other change made was the nth degree skid...which started the whole new drive shaft- adjustable contol arm-what's next.....process. Any ideas???

Also, the shock cans are very close to the springs and the track bar is against the gas skid. (which you all knew would happen) Is there any chance that the track bar and skid will work thier space "issues" out by themselves? Or, am I just going to break something? It seems to drive fine like it is.

Thanks again for the previous advice and in advance for any new thoughts,
Nick
Cut the spring perches on the axle. trim them back to the tube ensuring to keep a steady hand so as not to cut a brakeline. As for the track bar..An adjustable will be needed.
 
1 - 9 of 9 Posts
Top