Define the wobbles and shakes

Can someone define the difference between a suspension wobble and a driveline vibe? Just added 2" to an rc 3" lift. Now have a shake that starts about 50 mph through 60 mph. Shakes everything enough to make it difficult to tell. Re-rotated tires back to original positions, have checked all front end components and all are tight. Front axle is only 1/8" off to drivers side, will have adjustable trackbar with bracket tomorrow. Only thing not changed is the upper control arms. Lowers are iron man adjusted to 16 5/8" (was driven before adjusting from the 3" and it didn't change the shake). Does have a 1" tc drop. Thinking about increasing that to 1.5 or 2 just to isolate it. Rear has shims and shackles so angles should be good without binding. What am I missing. Do I need upper control arms? By the chart here They would only be 1/4" longer so the caster angle should really make no difference.
http://www.ilovejeeps.com/forums/showthread.php?t=12524

I have quite a bit of experience with tire and suspension problems and have always been able to tell what the problem is pretty quickly. This one I can't isolate.

if it feels like your car is shaking left to right, or if the shaking has a large effect on the steering wheel, it is most likely suspension/death wobble. Id assume that your new trackbar will fix this.

if at slower speeds, you can feel the vibration under hard acceleration, it is most likely your rear drive line.

Don't "fix" the vibes with a larger band-aid (read: transfer case drop). Just fish out the dough (as little as $100 shipped) for a SYE.

Driveline vibe usualy comes from the rear and doesnt affect steering. Feels like a vibration in your seat or floor, and is usual audible. Wobble is usually a lateral(side to side) movement in the front axle that can be felt in the wheel and can be pretty violent. Depending on what you are feeling, either one is possible with the ammount of lift you have.

Vibes can appear at 3 or 3.5 inches of lift without a tcase drop and 4-5 inches with a drop, (dont quote me, ive heard stories of vibes with less than 3" and no vibes at more that 5! This is just some decent "baselines")

Wobble is a little different. I have had stock jeeps encounter the front end "deathwobble"! It really has nothing to do with the fact that its lifted, but the fact that you have something in geometry of your suspension that needs to be corrected! It could be a caster issue, or worn steering linkage, or your axle could be off to one side and you need to adjust your track bar, or the track bar bushings could be worn even though the axle is centered correctly. It could even result from having your tire pressure not adjusted to an even level!

There are alot of good write ups on here regarding both of these problems. Hope you find the answers you are looking for!

~Ben

at 5" lift if I get a hack n tap, can I still use a stock front driveshaft for the rear or does it need stretched?

Did you adjust your toe? Can you confirm that your tires are balanced?
As for front d-shaft. I would fully extend it and measure. Also measure your current one from joint center to center. Should give you an idea.

yes, tires are balanced. I have triple checked toe, I am 1/8" toe in. If this overnighted trackbar actually shows up tomorrow I'll get it on (been 3 days to cross 2 states last time I pay for overnight) but current one it tight in every direction with no extra body movement. At any speed under 50 I can go over roads that are off camber on one corner of each axle very smoothly but on the smoothest road hit 52 and it starts, feels like a KMart shopping cart. Guess I'll start adding even more positive caster this weekend if I get a chance. My guess is right now it's between 6 and 8 degrees

oblivion_twister said:

at 5" lift if I get a hack n tap, can I still use a stock front driveshaft for the rear or does it need stretched?

Click to expand...

Yes at 5" of lift you can use a HnT with a front ds.

been doing some digging trying to figure out a cheap/easy way to read caster angle, came up with a $10 magnetic protractor like a welder would use, put it against a flat bottom on the lower ball joint and after subtracting the angle of the driveway it should tell the angle of the spindle. At least then I have some idea where it is.

trackbar is on, played with the toe a little bit and got the wobble down to a quarter of what it was. Will play more this weekend with toe and caster.