boomerang shackles and vibes

[blondejoncherokee]

im a little confused now, so i can figure this out, if i only shimmed the rear 3 degrees id be at say 8 degrees at the pinion and the same 5 deg at the tcase shaft. thatd be bad to have the pinion point up 8 degree and the tcase shaft point down 5. so hypothetically if i pulled the drop kit and say the t case is at like zero degrees, id want the pinion pointing down 3 degrees? so if the t case is at like 10 degrees pointing up, id want the pinion at like say 7-8 degrees pointing up, which would be like replacing the 6 degree shims with 3 degree shims?

 

[JNickel101]

you want to lower your pinion angle down to 2-4 degrees...with 3-4 being ideal.

reason being, when you hit the gas, your leaf springs will ever so slightly "wrap", and that will cause your pinion angle to tip up slightly. to me, it sounds like you need a 2* shim to push your pinion back down.

the TC drop is to reduce the angle of your driveshaft - once you start lifting higher, even IF you keep your pinion and TC output shaft relationship ideal, you'll get binding in your u-joints.

an SYE works 2 ways, it allows you to run a longer driveshaft (reducing the angle of your DS) AND it reducing the binding effect by using a CV type joint.

 

[xjbubba]

Blondejoncherokee, maybe a little Googling will help you understand.
Here's a start: http://www.drivetrain.com/driveline_angle_problem.html

 

[blondejoncherokee]

thanks guys for the help, after all your help i know i need my pinion another 3 degrees lower and i already thought the 6 degree shim was overkill, then i need like a or 9 degree shim on a 4.25" lift in the rear? the pinion did point way the hell up after i added the boomerang shackles though.

 

[blondejoncherokee]

ok, so after not realizing how fine and precise of measurements i need to take from my protractor( i thought maybe the angles would be way off by like 10 degrees) i remeasured far more carefully, and the pinion is between 3.5-4 degrees and the yoke at the tcase is actually more like 6-6.5, so that is actually where it should be. before i said both are at 5, but tcase is above 5 and pinion is below 5. so theres my 2-3 degree difference. so now im narrowing it down to the u joints? i just changed the pass side motor mount and the t case mount too, so maybe a combo of bad mounts and old u joint operating angles wore the u joints bad, and at this new angle it just aint workin for them? they feel tight, but maybe they wore to the old operating angle. im gonna replace em tomorrow and keep my eyes peeled for a cheaper yj slip yoke

 

[blondejoncherokee]

a driveline shop near by here in sac had a yj slip yoke for 50$ brand new and also gave them my measurements and they may or may not lengthen the shaft and are gonna check it for balance , along with new u joints. im hoping this will cure it, i told them i had my pinion down 2 degrees less than the tcase and they said they should be the same, but i told them i was accounting for axle wrap and they were still leaning towards having them be the same angle, but i thinking you guys make way more sense. i would hvae done the joints and yoke myself but so damn busy with work and i have a ton of other projects on the rig right now like getting the dana 44 on, so im gonna fork up the 120$ bucks for the sho to do it all(including lengthening) by the way, my dana 44 spiders are welded(not to the carrier) and i cant get the shafts out yet with all the brakes off and the axle retainging palte off, i thinking when the previous owner welded the spiders it heated the spiders to the shaft ? my buddy was telling me he did something similar in a welding class, but on purpose.
anyone had a similar problem?

 

[blondejoncherokee]

ok, got the yj slip yoke, lengthened the read shaft by 1/2 via retube, and new u joints, now i dont get vibes until like 65, but i still get em on acceleration,
angles are better too, like 4.5 at the case and 3 at the pinion . i dont get vibes on decceleratin, and i can go up to 70 without vibes, but sometimes not, its a little random. im thinking the old worn down swampers are outta balance again? i just got em balanced less than 2k ago, in june, but i took a few chunks out of the drivers side rear out on the trail before i bump stopped it and cut the fenders out a little more along with new shocks and used bushwackers for 50$, so is it possible that along with the few small chunks missing and some uneven wear due to the swampers nature, they prob need to be balanced and are giving me vibes at high speeds?
before i got em balanced i got death wobble at 35-45, so im guessing vibes at 65 could be an option
i also know the passenger rear bearings are going out, but im waiting to swap in the d44 so im not gonna waste cash for bearings for the d35. you cant tell by hearing it, but there is a little play.

 

[RCP Phx]

Post #2,option #5.You need a SYE kit.You have already spent about 1/2 the price of a PORC kit!

 

[blondejoncherokee]

ya, i just realized that and now im kicking myself in the ass. i dont know what i was thinking. ill prob go to a sye before june now...prob in the next few months