yah...vibes

blondejoncherokee

blondejoncherokee

NAXJA Member
Location
sacramento
alright. im kinda confused.
i didnt have vibes for so long. now they are back. yep. lame. just about anything over 65mph.
heres what i got so far.
adjusted toe in tonight
centered steering wheel(shouldnt make a difference but is nice)
pulling front shaft doesnt make a difference.
uppers are at 17"
lowers are at 18.5"
when uppers where at 17.5 i pretty much had no vibes but my trackbar was rubbing on the driver side uca mount when flexing. sucked bad. was loosening the trackbar nut.

front was about 5.5" or so at that point.
so i added another 1" of lift up front and adjusted the ucas back to 17".
it also straightened out my springs.
anyway the front lift is roughly 6.5"
the rear is somewhere between 3.5-4"
rear driveline angles are good.
front "castor" estimated angle in regards to gojeeps writeup is about 89-90* which is too much. it needs to be like 87.5 ish.
http://www.go.jeep-xj.info/HowtoAlignment.htm

i would like to actually drop the front about 1/2" (RE3.5 coils with 4 stock isolators)
and then add a leaf to the rear and maybe the commacnhe shackles i have too.
i know this would help stiffen my rear which is too soft.
it would bring the front down a bit and make control arm angles better.

but will it make castor better or worse?
could i be getting vibes from too much castor?
if so, how?
im also considering just going to a real sye kit and rebuilding the t case if getting the tires balanced doesnt fix it.

basically could too much castor and maybe a bad job on toe in cause vibes ???? or is that not possible?

im kinda at a loss for words.
the REcoils are old and very soft . the rear packs are probably worse.
but still it was on these same coils and same packs with no vibes a few months ago.

i also got some slight vibes for a bit from some loose uca nuts. but i locktighted them and tightened them back up. vibes went away for a while. drove all the way to santa cruz. on the way back got the vibes back.

anyone down to ride in my junk and give an opinion?
maybe at the meetngreet?
 
wait i misunderstood gojeeps article im supposed to be at like 84.5*
 
65 MPH and vibes? Welcome to the world of Jeeps, now get over it.

If you are running 5.5" of lift in the front without a hub kit you will most likely get vibes around this speed. On my junk I spent some time adjusting the front pinion angle only to screw up my caster angle and cause some really weird steering issues. I found a spot where the vibes weren't that bad, and the steering was OK and called it done.

Another issue is if you recently installed lower ratio gears in your axles. The driveshafts are spinning much faster with 4.56 or 4.88 gears than stock so the vibes will be worse.

Here is the big question, have you removed either driveshaft and drove the vehicle at 65 to see where the vibes are coming from for sure?
 
LOoks like he did pull the front drive shaft from the original post.. Hey Jon, did you change anything or did it just start out of the blue?
 
it started out of the blue on the way back from santa cruz 4th of july weekend. ive taken it camping and done some light wheeling recently in it before that. long drives no vibes. for months. then theyre back.
i plan on dropping the front 1/2"
i guess i need to pull the rear shaft sometime soon.
still had vibes with the front off, but they were not nearly as bad.
ill try pulling a 5/8 spacer outta the front and readjust my steering and trackbar. then throw a stock second leaf into each pack.

i guess i feel better that some guys have em.
but i had for a long time and replaced alot of stuff and now theyre back again.
i just want to go 65-70mph with no vibes!
 
and ive been driving with the 4.88s for a while now.
 
Jon,

Are you free over Sat, Sun, or Mon nights? You're welcome to swing by and I'll go on a test drive with you. We can drive mine too and see if you think it's any better. Are you running an XJ front shaft in the rear? I've got two, newly balanced that may be the right length... we can swap either in and see if that helps.

If it was vibe free w/ 17.5" uppers, but at 17" you've got vibes, what about shortening the lowers an inch to compensate?

Billy
 
that might be a good idea billy.
the lowers arent adj though so id either need to buy some adj lowers or get these cut down by someone. the point though was to keep the lowers as long as possible to help with the control arm angles but maybe i could drop a couple more 5/8" spacers off to make up for that. the only reason i threw so many on was to clear the trackbar. but if its clearing already who cares?
 
just got done adding the second longest leaf from a sagging stock pack and some comanche shackles. it looks alot better with the rear higher and its alot stiffer in the rear so it handles alot better. still have vibes. my rear ds angles seem great too.
still not sure what it could be.
next plan is to maybe pull a spacer from the front and drive it. then maybe pull the front shaft again and see if that helps.
 
im wondering if i dropped the t case like 3/8 to 1/2" if both driveline angles will get better and make the jeep vibeless again. id give up up to half an 1/2 of t case clearance for that. no more than that. i might try some washers.
ill remeasure the angles too.
i think the rear ds angle is 17-18* and the pinion is like 15-16.
fron i need to check.
-jon
 
Hey Jon, maybe you should take up Billy's offer to try a balanced rear shaft. if the vibes started out of the blue then its most likely the result of the last mods, which sound like many, and now stuff is starting to wear because of it. just a thought and its cheap. It may be something simple instead of changing a bunch more stuff and posssibly compounding the problem or sturring up more gremlins.. Good Luck man..
 
Update:
Rear ds angle 17.5
rear pinion 14.5

Front ds angle 9
front pinion angle 1.5

These are my angles
When ucas were at 17.5 my front ds angle must of been better.
I am thinking about dropping the T case half inch. To get the angles better for now and adjusting the uppers to 17 quarter.

Do you guys think the front drive angle would be causing the vibes or maybe even a combo of front and rear?
 
after some measurements and calculations
i figured this out
if i drop the tcase 1/2" it will drop both front and rear ds angles roughly 1*. good for the rear. since itll drop it down to 16.5 ds angle and the pinion will still be at 14.5
the front will be at 8*
but the front pinion is still at 1.5* which still sucks.
so im thinking about maybe lengthening the ucas a 1/4" to see if this bumps the pinion up a bit and shave a tad bit off the uca mount on the driver side.
or i could cut and shorten the lcas by 1/2" instead which will put the ds at the angle it was before i shortened the uppers.
and maybe then i wouldnt need the 1/2" drop anymore and maybe get some longer shackles for the rear to point the rear pinion up a bit.
 
My suggestion is to remove one driveshaft while trying to get rid of the vibes on the other shaft. It will make your life easier trying to figure out where the vibes are actually coming from. Back when i was running 4.56 and 33's, when the rear shaft stopped vibrating the front would start. Had a hell of a time figuring out that one.
 
wow. thats crazy bryan.
yah im figuring the rear is close to being good right now.
i dont want to drop the tcase so im thinking about longer shackles in the rear to point the pinion up a bit more and maybe get another 1-2*.
as for the front im leaning towards shortening the lcas by 1/2 to 5/8".
then if that doesnt get the front pinion within 3* of the ds angle ill lengthen the ucas by 1/8" -1/4".
if that doesnt work ill erbuild the tcase with a real sye.
 
soooo yur at 5.5" and no SYE????
 
ah ok. I was just a little confused when he said he wanted a real sye.
 
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