Vibes after SYE install

[Ghostrider]

OK, 2001 XJ. I lifted it (mild- OME JC1A + MJ shackles) several years ago and shimmed to cut down the vibes, I lived with it until I could afford an SYE. So here's the issue- before the SYE I had a funny "chuckle" sound at acceleration, and a low frequency hum/thrum at speed (70). Now the chuckle is gone (helps when the d/s is the right length!) but over 65 I have some vibes that were never there before. Also a vibe going through 35 (or thereabouts). Vibes disappear when you let off the gas, and seem to vary as the suspension flexes while traveling down the freeway. Should I have removed the shims that I installed to eliminate the vibes before installing the SYE? Or should they stay in there? Real experience please, not conjecture- I know with the number of folks on this forum with SYEs there has to be someone that can answer! Thanks.

 

[RCP Phx]

Most likely the vibes are changing do to axle rotation,you might try reducing your shims(pinion angle) by 1* or 2*!! What are your actual angles,the newer T-cases are harder to cure!

 

[Ghostrider]

It's been a few years since teh shims were installed. I think the shims in there are 2 degrees. Taking them out would put it back at stock pinion angle. Will that work with the MJ shackle in there? Opinions? Experience?

 

[LR_2000_XJ]

Are you sure you have as close as possible, 0 * at the pinion? That's what you need with a double cardan joint up top side of the DS. I just wanted to throw that in, though I didn't really check your degrees of shims to figure your results. hope you get the vibe under control. My mom's (yes, my mom's) XJ has a 3.5" RE lift and a hack 'n tap on the 242 TC for the DC RE DS, and she has bad vibes despite having close to 0* as I could get it at the pinion. I fount the splines were a bit worn at the hack site, so maybe it's time to upgrade to a true HD SYE when the wallet says I can. I did finally find the problem, it was the ball joint in the cardan joint between the two u-joints that needed to be replaced and had alot of play.

My XJ however is still using the stock DS at 4" and little vibes!

 

[THISISWEIRD]

You have seen the links like this, right?
http://www.highangledriveline.com/tech_corner_for_drivelines.html

Sorry, if I'm telling you what you already know, but a CV shaft means the shaft has zero angle between the it and the pumpkin. In a standard, U Joint (both ends) the pumpkin angle and the transfer case angle are equal or there about. You've got to get that yoke on the pumpkin pointed to the TC.

EDIT: I see I was beaten to the punch. Always a day late and a dollar short, I guess.

 

[icewolf73]

You have seen the links like this, right?
http://www.highangledriveline.com/tech_corner_for_drivelines.html

Sorry, if I'm telling you what you already know, but a CV shaft means the shaft has zero angle between the it and the pumpkin. In a standard, U Joint (both ends) the pumpkin angle and the transfer case angle are equal or there about. You've got to get that yoke on the pumpkin pointed to the TC.

EDIT: I see I was beaten to the punch. Always a day late and a dollar short, I guess.

X2.

Your pinion should be in a straight line with your driveshaft or slightly (maybe 1*) below. If your shims worked (somewhat) before you had the SYE you might still be at too great an angle between your DS and your pinion.

 

[djblade311]

no, actually the pinion should be 2* below the driveshaft. Why? because during acceleration and load, the pinion shifts up.

 

[icewolf73]

no, actually the pinion should be 2* below the driveshaft. Why? because during acceleration and load, the pinion shifts up.

Aftermarket leaf springs are stiffer/stronger than stock and tend to have very little axle wrap. 2* would be the very most I would allow since there are no control arms in the rear of an XJ. I lift Jeeps all the time that have CV driveshafts (most with coils in the rear) and we set them with around 1* or less. No vibes or issues from axle wrap. The guys I work with have been doing this much longer than I have. This is their advice also.

 

[LR_2000_XJ]

no, actually the pinion should be 2* below the driveshaft. Why? because during acceleration and load, the pinion shifts up.

X2 on this, actually I did forget to mention that I have someone on the brakes with the e-brake on too, and the Jeep in gear when I measure for a rough idea of what the angle is under actual acceleration. Also, with RE 3.5" leafs, it does change the angle by about 1* even though the leafs are heavy duty to me compared to my other Jeep with stock packs. I had done the mistake of making measurements before without doing this, and also with the weight of the Jeep in park facing down on the driveway, which changed the angle enough to cause the extra vibes it had. I learned my lesson there.

My question on this now is, would it be sufficient enough if I take the measurements while it's parked facing up the driveway? I have checked what the pinion looks like when the brakes are released after it's put into park and it definately moves up towards the TC. Is this a good similation of acceleration to take a good measurement?

 

[blondejoncherokee]

did you measure your pinion angle? t case output shaft angle? if you left the shims in thats no good, since before you wanted your pinon/output shaft angles to be equal, now you want your pinion to be 1-2* below the driveshaft angle. two different animals. you prob need to pull that 2* shim out and prob turn it around so the fat part is facing rearward. but i have no idea without measuring it. i went from a non sye setup in jan with a 2* shim (facing forward) that helped but still bad vibes to a sye in june with 4* shims, (fat part facing rear) i have tried alot of shim/shackle/tcasedrop/leaf spring combos over the past 6 months, about 11 different combos of shim/shackle/tcasedrop/leaf spring and i still need to tinker with it a bit, i still have my pinion 3.5* below the ds angle and after careful measuring a mj shackle will be like perfect for my setup. everysetup is different. measure and research and remeasure. dont be afraid to have to take those rear leaves off 2 times a day if you must.

 

[Ghostrider]

Thanks guys. I'll yank the shims and see what happens, then try flipping them around if I need to. Measured the angle but every time I do it comes out slightly different- old eyes and too small a gauge!

 

[blondejoncherokee]

i understand about the angle being differnet....i always measure it 10 ten times and take the average and throw out any wierd numbers that are way off. i think youre on the right track. but measure before you pull the shims and that way you dont have to pull the shims then put it all back together then add the shims and then put it alltogether again. for example say your rear pinion angle is at 8* with the shims, the ds angle is at 15*. if you pull em out youll be at 10*(since you had them facing forward) then if you basically turn em around(id reccamend replacing center pins while youre at it, youll be at 12*. so that 12* is good for now until you can afford a 4* shim or some lift shackles(commanche shackles will add + 1-2* of pinion angle roughly) to get you to about 14* below that 15* ds angle.