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another vibe thread, sick and tired of vibes, i really have no idea anymore

blondejoncherokee said:
thank you guys for all the help. ive been thoroughly researching vibe threads for months now and tried a ton of diff. t case drop and axle shim combos along with diff axle shim combos with different shims as well. i was just wondering basically at this point if i can get away with just a longer shackle to "shim" and point the pinion up towards the t case cuz im sick of swapping in degree shims. but honestly i wont know until i install the PORC sye and the rough country 1.5"-2" lift shackles. i will post up once i get the sye in and the shackles on what the angles are and like i said i have steel shims lying around now...i was originally trying to avoid the "cost" of a sye but after all the stupid money i put into shims and steel for drops and shackels and add a leafs and new driveshafts and junk i shoulda done the sye in the first place. i highly reccamend to anyone to just fork up the 200$ for the sye and be done with it instead of dealing with countless weekends of tearing apart the rear leaf packs on sundays to mess with angles and shims... anyone running a porc sye and 3" leaves with 2" shackles? if so what shims if any are you using on your leaves?
Click to expand...

I'm running 3" leaf packs w/ 1" jks boomerang shackle, SYE and 4* shims. Personally, I think it depends on how stiff your springs are, as to how much pinion tipping you get from your shackles. If your leafs are a little more stiff, they wont "give" as much, and the result will be slightly more tipping of your pinion. I wish i could help more, but honestly, its a really hard thing to predict. I had 2* and 4* shims to play with and was lucky that the 4* ones were perfect.
 
cool. thanks guys. i appreciate all the info. im gonna start with the shackles and then go from there. im hoping if i need em at all the 4* will work...
 
i replaced the lca bushings, all tie rod ends, and the track bar and it helped, but still have vibes. i have the stock uca's on the way with bushings pressed in, along with the axle side uca bushings. i also have some 297 axle shafts and a driver side bearing to throw in as well. after that i think ill throw in a 2* shim in the rear since according to my measurements the pinion angle is at 6* and so is the tcase output. so a 2* will put me good i think, and the 4* i had on there was too much. the only times i get vibes are under heavy acceleration and specifically uphill. oh, yah, i was gonna do the leaf spring bushings as well.
 
is your a auto? i had the same kind of thing after searching for months i found the torque converter to flex plate bolts were loose ,tightened them up vibes all but went away ,just a thought
 
blondejoncherokee said:
i replaced the lca bushings, all tie rod ends, and the track bar and it helped, but still have vibes. i have the stock uca's on the way with bushings pressed in, along with the axle side uca bushings. i also have some 297 axle shafts and a driver side bearing to throw in as well. after that i think ill throw in a 2* shim in the rear since according to my measurements the pinion angle is at 6* and so is the tcase output. so a 2* will put me good i think, and the 4* i had on there was too much. the only times i get vibes are under heavy acceleration and specifically uphill. oh, yah, i was gonna do the leaf spring bushings as well.
Click to expand...

If your tcase output is at 6* and your pinion is at 6* and you are not running an SYE that should be perfect. Remember the 2* below the pinion is only for when you are running an SYE.
 
so the 2* below is supposed to be sye only huh? weird. yah, im like positive ive got em both around 6*. so i dont want a non sye setup to be 1-2* under then huh? well im about to do the uca's and bushings and some 1990 2wd chevy front brakelines along with new hard lines that ill be making since the old ones are shot and i get em off. then ill throw the 2* shim in the rear and see what happens. if that doesnt fix it then its sye time.
 
blondejoncherokee said:
so the 2* below is supposed to be sye only huh? weird. yah, im like positive ive got em both around 6*. so i dont want a non sye setup to be 1-2* under then huh? well im about to do the uca's and bushings and some 1990 2wd chevy front brakelines along with new hard lines that ill be making since the old ones are shot and i get em off. then ill throw the 2* shim in the rear and see what happens. if that doesnt fix it then its sye time.
Click to expand...

Yes 1-2* is for SYE with a CV drive shaft. Do you have an angle finder. You can get them at any hardware store and will take the guess work out of all of this. If the angle look good on the angle finder then its most likely not your d shaft angle.
This is good info:
http://www.4xshaft.com/driveline101.html
http://www.4xshaft.com/tech_slopesVSangles.html
 
Last edited:
The 1-2* low for axle wrap applies to a std 2 joint shaft also!
 
yes i have an angle finder, thats how i know both are at 6*-ish. and honestly i agree with rcp phx i still believe that a non sye axle can "wrap" im gonna swap in those 2* shims . its possible that my measurement could also be off a bit, the magnetic angle finder can be hard to get exact. i think the pinion could even be like 1/2* over so that would be causing vibes so the 2* shims would fix that hopefully. ill get to them after i finish the new uca's and redoing the front brake lines with longer 2wd gmc lines and the hard lines from the proporting valve. i think the added weight of the dana 44 could be putting a hurting on these old sagging soft rustys 5 leave packs in the rear and the 2* shim will help em point back. i thought with a yj slip yoke and new shaft and joints, new motor mounts, lca and uca bushings, all new steering and track bar, new unit bearings up front, and tranny mount the vibes would be gone. nope. but at least the thing steers straight as hell and is as smooth as i could want steering-wise now!
 
UPDATE:
i just installed new 2* shims , so the pinion should be about 1.5* down lower than the t case output shaft.
did the driver side uca. and the driver side hub with a 297 shaft.

STILL HAVE VIBES, BUT NOT AS OFTEN AND NOT AS BAD, BUT THEY STILL SUCK AND I STILL HAVE THEM! I HATE IT...

so ive done the lca bushings, the drivers side uca with new frame end bushing
all new tie rod ends except drag link at knuckle tre, but no vibes in steering wheel, the steering is tight.
new driver side rotor with the newer style hub.

i dont know, do 89's with 3" lifts often have vibes bad enough to do a sye? i think thats what i need next...

 
ill check that, but from starting it and reving it there were no vibes i could notice but i wasnt looking for em either...
 
the vibes are pretty much only after60 mph, maybe even 65 if im lucky, and pretty much only under heavy acceleration, or acceleration uphill.
 
blondejoncherokee said:
a sye? i think thats what i need next...
Click to expand...

No, that's what you needed a month ago.

Really.

I tried to resist it, too. But it really is inevitable...

Bite the bullet, do the deed...

Robert
 
so basically i can go from no vibes to vibes on the same setup and pretty much need a sye. its weird that in dec i had vibes. then threw a shackle on with a shim to kick the vibes from the shackle, helped, but i still get vibes. i pulled the shackle and shim and went back to 3" and had worse vibes??!?!?!?!?!?! i then tried an add a leaf and 4* shim, still vibes and made the rear lifted 7"'s. then pulled the add aleaf and the t case drop and just tried the 4* shim with no drop. worse vibes.
i should have never messed with the thing....i was hoping it was some other moving part or bushing thats cheaper....i guess the rear output shaft could be bad or something huh? or maybe something in the t case got worn out enough to make it vibe? i guess ill be giving porc a call in a week or so....
 
ill tell ya what, if the sye dont cure the vibes ill really have to nowhere to go. that was my cure all, wait till youve exhuasted everything but it will work for sure solution! at least after 4 different leaf spring/axle shim/shackle combos ive gotten really good at measuring and shimming the rear to keep it 1-2* below the t case output. i have some steel 2 and 4 * shims to play with for the sye, and some rough country shackles(sold the RE boomerangs) and a spare front shaft...you guys rock for advice and anymore input is always welcome. at least the thing handles better than ever while vibrating...
 
ok, so i remeasured the angles after the 2* install today. the t case output is at 6.5-7* and the pinion is 5.5-6*. so maybe i shoulda thrown in a 3*?
 
ASLSYE.jpg


:D

Robert
 
a sye is in the works already. i found a guy with a hackntap i can have and i might go to rubicon express tomorrow and buy an adjustable track bar too....
 
That'll be better than nothing, but you were also wondering if the shaft itself might be bent.

A H&T will reuse that shaft, a shortshaft kit will replace it with a known good.

And I thought the AA had dropped to like $250...

But hey, if you don't have $250 (been there!) the H&T is alot better than the slipyoke!

Good luck,

Robert
 
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