Currie 4 inch Springs and SYE Vibrations

box12360

box12360

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Original poster
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Nov 12, 2018
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Florida
Recently installed a 4-inch lift Metalcloak adjustable arms, track bars. 4 Inch Currie Springs. Adams driveshaft (used was on this exact axle but 3.25-inch lift instead of 4-inch), rough country SYE (really good price on the sye could not pass it up). 35 Inch Tires

I took it to a local Jeep 4x4 shop to have the alignment done after I installed the lift. They tried different pinion angles within the range up and down a few degrees and it's still getting vibrations. They installed a 1-inch skid plate drop and said it went away but had just a slight vibration at 60 also said it could have been the new tires. They took the skid drop off when I went to get the jeep (it was for a YJ all the holes did not line up) if that matters lol.

Prior to putting the lift on I had the drive shaft and sye on for a short period of time with my 2-inch lift and 31's.

I've ordered Browndog rubber 1-inch motor mounts to try and get the pinion down. Coming in next week. I also went and got washers/longer bolts to make a temp skid drop kit.

I really don't want to lose the clearance and drop the skid plate.

My question is should there be a vibration with a sye installed and pinion angle set correct? Has anyone else had this problem?
 
I had a bad vibration recently and it was driving me nuts. It was just the tires. Were your new ones spin balanced or road force balanced?
 
I've got no vibes. Something is up if you have vibration. When first adjusting my pinion to get rid of the drop the Jeep had when I bought it you could feel the heat in the pinion bearing after a very short trip. After an adjustment it's much cooler even after a long drive.
 
like @LittleTankTJ said the first thing I would check is the tires. Next, I would pull the front shaft and see if the vibs go away. If not reinstall the front then pull the rear shaft, put it in 4 high and test again. At least then you will know which axle needs adjustment. I also run a currie 4 inch lift, sye, and MC arms. No vibs but it took a lot of dialing in to get there.
 
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I have beads in the tires. They did the test by removing each drive shaft and test driving. With the rear removed it rode fine with no vibes.

I did just put in washers on the. Trans skid that lowered it 1 inch and that helped out greatly, it still have some vibration around 60+. Maybe the tires?
 
How much lower than the diff will the drive shaft ghng if it's not connected to the diff? Could it be your DC is binding? Did you check the centering ball on the DC?
 
box12360 said:
I have beads in the tires. They did the test by removing each drive shaft and test driving. With the rear removed it rode fine with no vibes.

I did just put in washers on the. Trans skid that lowered it 1 inch and that helped out greatly, it still have some vibration around 60+. Maybe the tires?
Click to expand...
It sounds like your angles are off. Im going to assume the shaft is fine since it worked vib free before the lift. What is the angle of your ds and the pinion. The easiest way to find pinion angle is to put an angle finder on the back of the case on the machined flat area next to the diff cover.
 
How old is the driveshaft? If you ran it for a long time with the smaller lift the u joints may have " worn in" to that angle. I have had this happen to me . The u joints felt fine, but were old and used to running at the original angles. New joints took care of the vibes. This could be your problem.

You do need to check your angles. Rear u joint should be 1 degree or less but not pointing up.

Google double cardan u joint angles if you need a visual . There is tons of info out there on setting rear u joint angle properly.
 
So this weekend I adjusted the angles, they were off 6-8 degrees but to the shop's defense, I did lower the trans skid and inch. I adjusted the pinion angle to about 1-2 degrees lower. A lot of the vibrations are gone but I'm still getting a little vibration around 50+ mph.
My tires are bead balanced so I've tried shifting into neutral when the vibration starts and it seems to go away.

The driveshaft was on the previous setup maybe 500 miles.
 
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Try to get the pinion less than 1 degree down from the driveshaft but not any higher than 0 degrees.

They u joint needs to move slightly to keep the needles from wearing into the cross excessively. Bearings like to turn.

0 degrees would be the smoothest, but the u joint needles would not move.

There is a lot of info out there about how u joints work. They actually speed up and slow down during each driveshaft revolution. The 2 joints at the t case in a double cardan cancel each other out, but the single at the axle is on it's own. That is why angle at the axle joint is bad. There is not another joint to cancel out the acceleration and deceleration the u joint sees.

I believe Spicer actually recomends 3 degrees to be the optimum angle for u joints for life expectancy. This amount of angle keeps the grease moving in the joint and makes the needles turn......but we cannot run 3 degrees with a DC style shaft.
 
98628


Your pinion and driveshaft angle should match at the pinion. This is from Tom Woods site. MAybe 1 degree less but you should shoot for 0 degrees at the pinion.
 
Your pinion and driveshaft angle should match at the pinion. This is from Tom Woods site. MAybe 1 degree less but you should shoot for 0 degrees at the pinion. One reason to have the sye with 4" lift is to get rid of the skid drop. With SYE you need to adjust your pinion angle, not drop the skid.

I hate when I go to edit and accidentally reply.
 
BillNyeIsHigh said:
Your pinion and driveshaft angle should match at the pinion. This is from Tom Woods site. MAybe 1 degree less but you should shoot for 0 degrees at the pinion. One reason to have the sye with 4" lift is to get rid of the skid drop. With SYE you need to adjust your pinion angle, not drop the skid.

I hate when I go to edit and accidentally reply.
Click to expand...
I agree I was kinda stunned when the shop said it was vibrating so bad.....
 

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