• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

boomerang shackles and vibes

blondejoncherokee

blondejoncherokee

NAXJA Member
NAXJA Member
Location
sacramento
anyone running a similiar setup???
i have a 89 4.0 231 auto 3.55's, 33's, lotsa trimming, 1 inch t case drop .....im running 3" coils/full packs. 5" lift shocks with limit straps....i recently added boomerang shackles and now have vibes. i added 6 degree shims (no sye, so the fat part of the shim faces the tcase, skinny part backward)which kicked the vibes back to about 55-60mph, but before the shackles i was going 75-85 with no vibes at all.
so im thinking about a few options:
1.adding say mj shackles(1/2 net lift) and 3 degree shims(or no shims at all?)
2.maybe i overshimmed and should try 4 degree shims?
3. replace the u joints and see if that fixes it? the joints are tight, but ive heard that they can wear a certain way and adding more lift can piss em off and make em vibe.
4. throw the stock shackles back on, pull the shims, and lose the extra rear articulation, maybe that 1" of lift aint worth the vibes?

these are my cheapest solutions.
im leaning towards mj shackles if they really do add 1/2 of lift,a nd maybe no shims?
 
5.Gain all your ground clearance back by buying a SYE kit,removing the TC drop and rotating the pinion up!And enjoying your additional lift!
 
sye would be nice, i just dont have the cash right now. i figured i could fix it cheap with some shims and shackles for now, and not do the sye for another year...
 
Maybe you should try measuring the angles of the driveshaft, pinion and transfer case.

This will show you what degree shim you should be using.

Guessing isn't the smartest way and u-bolts are only meant to be used once. I have used them over a few times and had one break.
 
shims are right. without a sye you want your pinion angle and t case angle to be parrallel. i think im gonna swap in the stock shackles or mj shackles and pull the shims just for now, i drive it to the bay area alot from sac and i need the vibes gone asap.anyone have any mj shackles for sale btw?
 
6* sounds like WAY TOO MUCH.

Can you get us some pictures?
 
remove the shims and t/case drop completely and see what you're vibrations are so you can set a base-line for your troubleshooting adjustments... first place i'd look is at your stock XJ slip yoke.. they bind on themselves at around 4.5" of lift or so.. i've run a few XJs with 5" in the rear with no shims or drop kit with a simple YJ slip yoke swap. t/case drop would be next step.. then a small shim.. one change at time to see how each item has an effect positive or negative.. we worked on an XJ last month that had "self clearanced" its own slip yoke by close to 1/2" just by binding on itself and a moron behind the wheel not being aware of his vehicle. you should be able to get a YJ slipyoke for a few $$ from someone local.. do not pay $85 for the RE "extended slipyoke" its simply a copy of a stock YJ item.
 
just picked up an angle finder, now i need to go pick up some stock t case bolts. ive never been a fan of the t-case drop, but it was on the jeep when i got it. a local jeep wrecker here in sacto has the yj slip yoke for 50$ that ill grab tomorrow, and ill pull the 6 degree shims off this weekend, should i throw on new u joints while im at it?
 
re-use the current t-case cross member bolts. There is ample room for them to thread in.

New u-joints isnt a bad idea. Buy quality, moog or precision or spicer.
 
ok, so i just measured the driveline angles, and i measured the slip yoke angle, and the angle from both the slip yoke knuckles, they all read about 5-6 degrees, then i measured the pinion angle via the pinion yoke knuckle, top and bottom, and i get also 4-5 degrees, so the angles are all good? well maybe the u joints were worn a certain way for the 3" lift and now with the shackles added even though they are tight they could cause vibes?, could i just need new u joints? or did i measure from the wrong spots? the top of the diff is also 4-5 degree, so im guessing the pinion angle really is like 4-5 degrees, and the slip yoke is definetly at 5 degrees as well.
 
if i try to measure from the tail cone of the tcase i get like 10-11 degrees?
 
my driveshaft angle is 15 degrees, and my pinion angle is 5, my slip yoke angle is 5 also
 
so since the angles are the same it should be the u-joints? i havent lengthened the rear shaft yet either, could that be it? ill prob pick up the yj yoke and some new u joints tomorrow and see if that kicks it
 
DO NOT PAY $50 for that slip yoke.. check out your local club forums.. YJ guys have them laying around because they do SYEs all the time.
 
Your pinion angle needs to be lower than your transfer case output angle. This is required to account for spring wrap that occurs under acceleration, and under torque loads experienced at higher speeds.
The rule of thumb is your pinion should be 3 degrees max, below your transfer case output shaft.
 
You must log in or register to reply here.

Similar threads

S
Humming noise after SYE
2
Replies
32
Views
6K
Rockwood
R
W
2” Budget boost and rear leaf pins: do i need to replace them?
Replies
6
Views
1K
Woodswanderer
W
T
Death Wobble Questions (I searched first)
Replies
11
Views
3K
Anak
Anak
Jeepguy91
Huge list of parts for sale
Replies
0
Views
550
Jeepguy91
Jeepguy91
C
Before I Get the Head Milled (Overheating)
2
Replies
31
Views
8K
maxbraketorque
M
Back
Top