driveline vibration

adam greene

adam greene

Well-Known Member
Joined
Sep 9, 2008
Location
morganton
I have a 02 wrangler 4 inch lift. When I got it stI'll had stock control arms. Yesterday I got to installing lower control arms front and rear. Now I have a bad vibration I put new joint in driveshaft today to rule out that. I also have a trans drop. Do I need upper arms to get it back to factory?
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20141129_160853.jpg
 
Are they longer than the stock arms?
If it was fine before and now you have a vibration after changing arms thats the first place to look. Your pinion angle needs to be the same as the output shaft angle coming out of the case. So yes youmay need adjustable uppers now since you cant adjust the lowers.

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Yea there 3/4 longer I'm pretty sure. They sell 4 inch kits with just lowers I've ran them before with a transfer case drop never had any problems. But I know what ur saying just didn know if maybe the lowers caused something else to show up.
 
"nova" is spot on. Just by the pick it looks like to great a difference in the two joint angles. 2 degrees variance is about all you can get by with. Shorter the drive line the more critical that becomes. Last mod/ first problem. Usually where I start.
 
Looks like the pinion is too low. SYE will make that worse. Only reason to SYE is if you're getting bind at full droop. You'll need adjustable uppers and lowers then.
 
I'll try to get more pics and angles on them tom if I get a chance. Didn have a problem with stock arms so might just put them back on for now until I can find some adjustable uppers
 
Agreed on the adjustable uppers. That is always the first thing we recommend after a lift. If the vib is still there after the uppers are installed, I would recommend a SYE and CV shaft.
 
I agree your angles dont look that far off. (I have seen worse angles not vibrate!) I would recommend doing the SYE first. You'll want one anyway. Pretty much always need to SYE over 3" lift.

Generally, with a 4" lift...with the driveshaft angle and short length that it is, the driveshaft is pulled so far towards the end of the output shaft. Then that long ass output shaft will start to try to revolve around a geometric center. (like taking your index finger and rotating it in circles!). With the the old stock arms, with the softy bushings, may have masked some of the vibration that was there all along.
 
Pretty sure this Jeep just got totaled.
 
Seriously??
shawn said:
Looks like the pinion is too low. SYE will make that worse. Only reason to SYE is if you're getting bind at full droop. You'll need adjustable uppers and lowers then.
Click to expand...
 
WARRIORWELDING said:
Seriously??
Click to expand...

About which?

I didn't SYE until we did the tummy tuck and the driveshaft couldn't make the turn at droop. No reason otherwise.

And yes, most of his problem was due to the fact the aftermarket fixed lowers are all built longer than stock. That rotates the pinion down, making the angles at each end unequal. SYE doesn't change that, it just means that the pinion has to be rotated up even further.
 
SYE allows the driveshaft to be longer and removes the long out put shaft from the equation. The long unsupported length of the output shaft is definitely a cause of vibration. Remember that a U joint doesnt move with a constant velocity. They start and stop twice thru each 360 degrees of rotation. Hang that out on the end of a long shaft and you can visualize what havoc the would raise! Will behave much like a long shaft chucked into a lathe without supporting the other end!

As far as pinion angles and out put yoke angles being the same. I have heard this argument for years. And have never seen a consistent correlation to this and vibrations. Nor have I seen very many lifted vehicles where both yokes were the same angle. Vibrations seems to show up in some and not in others. I dont know if the CV style used in the SYEs eliminates the output angle requirements. I might guess it does. CVs only vibrate when the pinion doesn't aim straight at the CV. There is no regard to the output yoke angle what so ever.

And BTW...was it totaled?
 
I understand all the vibration bits and I've worked on quite a few different drivelines, even custom stuff on equipment and pto's ect. ect. didn't expect to read recently totaled. So how bad is it? Peices or something left to sale?
 
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