SYE vibes

[Sleeper]

Ok it starts with i bought the xj with a rc 4.5'' lift and it had bad vibes on the highway about 65 and above. I wrote it off as having a t-case drop and no sye.

I just lifted the rear to 6'' and it got worse and was around 30MPH and above, so i bought an SYE like i wanted to anyway. Well i installed it today and i still feel vibes while on the throttle at the same places, not as bad but still there.

The front has yet to be lifted to 5.75''. It does however have the LCA's by RC lift and stock uppers. Now i know i will need udjustable uppers for the pinion angle but only whne i can afford it. My adjustable Tbar is on it's way as well.

Do i have to shim the rear? Adjust the front pinion angle, It looks a lil off. My ball joints are shot but that is not causing it i beleive.

So where would you start? I will prob rip off the front DS and drive it tomorrow but since it has been there with the original rc 4.5'' and has gotten worse i would assume it is driveline associated.

[cityslicker]

I thought you didn't need shims or t case drop if running the sye?

[tjblair]

I thought you didn't need shims or t case drop if running the sye?
You shouldn't. (at least not at 4.5, maybe at 6in you would)



Are you stacking lifts?:090:
At 6in of lift you should really be going with long arms. But as a bandaid, I would think that if you were to either drop the back back down, or raise the front it should get better. With it raked that much you are making the rear angles worse.

[Sleeper]

You shouldn't. (at least not at 4.5, maybe at 6in you would)



Are you stacking lifts?:090:
At 6in of lift you should really be going with long arms. But as a bandaid, I would think that if you were to either drop the back back down, or raise the front it should get better. With it raked that much you are making the rear angles worse.Stacking? Alot of guys run 6'' without long arms, eventually i will but not now. RE lifts above 4.5'' are usually raked from what i see. And from what i read some people have shimmed Mike going above 5''

[tjblair]

How are you going from 4.5 to 5.75 in the front? spacers on top of lift springs?(stacking) I'm not saying that you can't do 6in of lift on short arms, But 4-5 inches is about the max on the short arms. And yes some kits are raked, espiceally when they are first installed. but 1.5 -2 in raked is a bit much.

Also have you checked the pinion for play?

[Sleeper]

How are you going from 4.5 to 5.75 in the front? spacers on top of lift springs?(stacking) I'm not saying that you can't do 6in of lift on short arms, But 4-5 inches is about the max on the short arms. And yes some kits are raked, espiceally when they are first installed. but 1.5 -2 in raked is a bit much.

Also have you checked the pinion for play?Ya, spacers. first time i heard "stacking". I might just do the DB's until i get long arms but for now prob just adjustable lca & uca's.

I agree it is raked too much but i had the prob before i did the rear a lil more. I just went out back at work and checked the slip yoke on the front DS and it is toast:072:

[tjblair]

Ya, spacers. first time i heard "stacking". I might just do the DB's until i get long arms but for now prob just adjustable lca & uca's.

I agree it is raked too much but i had the prob before i did the rear a lil more. I just went out back at work and checked the slip yoke on the front DS and it is toast:072:
The slip yoke is most likely your problem.

Stacking spacers on top of lift springs usually will cause more problems than it is worth. Yes it is a cheap way to get more height, but you are changing the geometry designed into the kit. And ride quality suffers. If your are set on doing the front this way, I would definitly do cam bolts,and adjustable uppers. Also you are going to have to do some type of track bar drop bracket at the frame end of the trackbar. You will probably end up running into clearance issues between the tierod and lower swaybar mounts when it droops out. You will probably need a diferent pitman arm too.

All of these issues are adressed with a quality kit. that is why I'm not a fan of just tossing spacers on an already lifted jeep. JMHO

[jlovbasz3]

Make shore universal joints are lined up correctly if they are off that will cause a vibration.

[tjblair]

^Also true, BUt I thought it was a new DS so I asumed it was in phase.

[ridgerunner97]

If you have a CV rear shaft, correct me if i'm wrong, does the pinion on the rear axle not have to point DIRECTLY at the Transfer Case output? On a normal shaft you can't do that because it puts the Universals out of phase, but that is how you have to do a CV shaft right? That may be the problem...

[tjblair]

If you have a CV rear shaft, correct me if i'm wrong, does the pinion on the rear axle not have to point DIRECTLY at the Transfer Case output? On a normal shaft you can't do that because it puts the Universals out of phase, but that is how you have to do a CV shaft right? That may be the problem...
Correct.......Well you want the rear most u-joint as straight as possible.

I dont know how you would get a regular DS (or one piece shaft) out of phase unless it is twisted.

[XJchris98]

If the rear is lifted 6" and you dont have any shims under the springs, thats likely where your vibrations are coming from. Once you do the SYE, you need that rear driveshaft pointed just a few degrees BELOW the transfer case output yoke.

The reason for this is, that if your using a combination of shackles/springs (or just worn out springs) to get your 6" of lift, the axle is likely twisting some when you accelerate throwing the angle between the driveshaft and transfer case out of line. This is assuming however that the axle output yoke and transfer case output yoke are already pointed directly at each other. If your not using any shims at 6" of lift, I doubt this is true.

If your using a set of really stiff springs you can probably get away with just getting the axle yoke and transfer case yoke in alignment. Thus not worrying about setting the axle a few degrees below the transfer case yoke.

If you dont have shims in there now and plan on buying some, PLEASE PLEASE PLEASE make sure you get steel shims that require you to run the centering pin of the springs through the shim. The ideal solution would be to just pull the axle, cut the current perches off, and weld new ones on at the correct angle without having to use shims. Its really not that bad of a job for anyone with a welder and a little knowledge of what they're doing.

[Sleeper]

The slip yoke is most likely your problem.

Stacking spacers on top of lift springs usually will cause more problems than it is worth. Yes it is a cheap way to get more height, but you are changing the geometry designed into the kit. And ride quality suffers. If your are set on doing the front this way, I would definitly do cam bolts,and adjustable uppers. Also you are going to have to do some type of track bar drop bracket at the frame end of the trackbar. You will probably end up running into clearance issues between the tierod and lower swaybar mounts when it droops out. You will probably need a diferent pitman arm too.

All of these issues are adressed with a quality kit. that is why I'm not a fan of just tossing spacers on an already lifted jeep. JMHOI plan on getting a drop bar whne i fond one at a decent price, until the ni will have to run the RE 1600. I will take the drop bracket on axle side off from the rc drop that was on there when i bought it. I have a drop pitman arm on right now. Aand i do need upper adjustable control arms soon as well.


Make shore universal joints are lined up correctly if they are off that will cause a vibration.I will provide some pics of the front and rear....


If the rear is lifted 6" and you dont have any shims under the springs, thats likely where your vibrations are coming from. Once you do the SYE, you need that rear driveshaft pointed just a few degrees BELOW the transfer case output yoke.

The reason for this is, that if your using a combination of shackles/springs (or just worn out springs) to get your 6" of lift, the axle is likely twisting some when you accelerate throwing the angle between the driveshaft and transfer case out of line. This is assuming however that the axle output yoke and transfer case output yoke are already pointed directly at each other. If your not using any shims at 6" of lift, I doubt this is true.

If your using a set of really stiff springs you can probably get away with just getting the axle yoke and transfer case yoke in alignment. Thus not worrying about setting the axle a few degrees below the transfer case yoke.

If you dont have shims in there now and plan on buying some, PLEASE PLEASE PLEASE make sure you get steel shims that require you to run the centering pin of the springs through the shim. The ideal solution would be to just pull the axle, cut the current perches off, and weld new ones on at the correct angle without having to use shims. Its really not that bad of a job for anyone with a welder and a little knowledge of what they're doing.i have a set of stiff RE 3.5''s on there with i assume rc adjustables shackles set to the first (1") hole and iam sitting at roughly 6'' i beleive. I replaced the front ds today since the slip was bad on the old one so i wll have to see how that works out when i drive it later. As far as the shims go if need be those are the ones i will grab.

Again i will post pics of my front and rear angles. I do see that my exhasut is very very sloce to the uni-body do you think that coiuld also cause some vibes being i cut the pipe four inches after the muffler which has holes in it? lol

[Sleeper]

http://img401.imageshack.us/img401/6523/syeinstall012.jpg (http://img401.imageshack.us/i/syeinstall012.jpg/)

[Sleeper]

http://img341.imageshack.us/img341/4917/syeinstall009.jpg (http://img341.imageshack.us/i/syeinstall009.jpg/)

[tjblair]

holy shit! I feel like I'm looking thru a microscope. LOL

[Sleeper]

http://img688.imageshack.us/img688/7996/syeinstall011x.jpg (http://img688.imageshack.us/i/syeinstall011x.jpg/)

[Sleeper]

holy shit! I feel like I'm looking thru a microscope. LOL
lol, i fixed it:045:

[tjblair]

looks like you may need to shim it up a little. And I would get that string,or twine or what ever it is off of your pinion before it takes out the seal.

[tjblair]

Oh my bad now I see you posted pics of front and rear. THe rear doesn't look bad. the front needs tilted up. you might be abl to get enough adjustment out of a set of cam bolts. If it push your caster to far forward.

[Sleeper]

looks like you may need to shim it up a little. And I would get that string,or twine or what ever it is off of your pinion before it takes out the seal.lmao, i did not even see that, thanks!
So you think i need to shim up the rear then? What about the front?

[Sleeper]

Oh my bad now I see you posted pics of front and rear. THe rear doesn't look bad. the front needs tilted up. you might be abl to get enough adjustment out of a set of cam bolts. If it push your caster to far forward.
OK i posted before i saw your second post. So the rear looks ok and no shims and the front pinion needs to come up corerct? Adjustable uppers? Esp when i go a lil higher

[tjblair]

OK i posted before i saw your second post. So the rear looks ok and no shims and the front pinion needs to come up corerct? Adjustable uppers? Esp when i go a lil higher
Going off of the pics, ya.

[Sleeper]

Going off of the pics, ya.Cool, i will have to see when i drive it more and higher speeds if it is still doing it as bad with the nes fornt slip yoke. It seems smoother since i did the sye and took the x member drop out though. Thanks