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Front driveline vibes after Currie lift install

5K views 36 replies 8 participants last post by  METT-TC 
#1 ·
So i did Currie kit for a friend. 4" springs lift, 8 double adjustable control arms, yada, yada. No SYE yet. Getting front driveline vibes. Low Pinion Dana 30. I read that pinion and caster are 12 degrees apart. I put angle finder on those circles right/left of diff cover. Set -7.2* pinion, which makes +4.8* caster. Pinion is pretty much pointed right at diff case. Uppers are not binding. Should i lessen caster angle? Increase to 5.5*?

Any help would be appreciated.
 
#2 ·
Pay no attention to the angles some angle finder says, they are just confusing 90% of the time. Simply put, the pinion angle takes precedence over the caster angle every time. Set the Caster angle as high as you can until vibes are encountered then back it off a degree. The front pinion angle can be no lower than the driveshaft angle since it deflects downward under acceleration which would make its angle excessive and cause u-joint vibrations. The front pinion angle can point as high as 1-2 degrees above the driveshaft but that's it.
 
#4 ·
So i did Currie kit for a friend. 4" springs lift, 8 double adjustable control arms, yada, yada. No SYE yet. Getting front driveline vibes. Low Pinion Dana 30. I read that pinion and caster are 12 degrees apart. I put angle finder on those circles right/left of diff cover. Set -7.2* pinion, which makes +4.8* caster. Pinion is pretty much pointed right at diff case. Uppers are not binding. Should i lessen caster angle? Increase to 5.5*?

Any help would be appreciated.
Seems odd that the pinion would be pointed directly at the T-case. Positive caster is steering knuckles rolled back (or pinion down). Guess I would have to see that.

I have the same lift and mine is set at 5 degrees positive caster and its not pointing at TCASE, pointing under it. It is a Rubicon and an LJ, so that could be the difference.
 
#5 ·
The front driveshaft is a CV, on all TJs, so the pinion must point directly up it and point directly at the t-case. The knuckles are welded on by the factory to give the proper caster angle with the pinion pointing correctly at the CV (t-case) as it must.
 
#7 ·
I adjusted 1° up from inline with driveshaft, test drove, and it's still happening. Adjusted to +2°. About to go for a drive. Btw, this vibration only happens under acceleration.

So dude from Savvy said for steering wheel vibration I should be checking trackbar and steering components. No excessive play. Trackbar is tight. Axle is centered. Axle is square to frame. He said other possibility is that this revealed bad ujoints/driveline components. I will say his previous shocks were beyond gone. A couple were practically floating. Zero rebound left. Rear trackbar relocation bracket was loose. Besides a lot of clanking, his jeep had no major vibes.
 
#8 ·
Still happening. So here's a question: how do I even know it's front driveline without removing it? And how would front driveline make the steering wheel shudder under accel when in 2H?
 
#9 ·
I had a vibration in my rubicon after a 4" lift I also have all adjustable control arms and I thought it was my rear DS and that I needed to readjust the rear arms but before I got to it my front DS developed angry sparrows so I pulled it to service it and had to drive my jeep without for a few days and lo and behold no more vibration so I took the front DS to a repair shop to be checked out and it turns out it was out of balance, there was no sign of any missing balance weights and it was not bent but the lift must have been enough to bring out a vibration. Had it re balanced and no more problems so you might want to have yours checked it might save you some work
 
#11 ·
Thanks man. Good info.

My friend (it's his TJ) is ordering a Teraflex SYE/Driveshaft combo from Adams as we speak. Here's why:

1) Driveshaft actual angle is WAY too steep.
2) D44 rear pinion is 1" longer than D35, thus putting more angle on each cardan (for tcase and pinion angles that cancel)
3) His tcase drop is only 1/2" and i'm thinking his 3" lift might have been only 2"....regardless

The rear pinion is parallel with tcase output and rear driveshaft absolute angle is 27 degrees!!!

Jeep will not be getting driven until Adams stuff gets here.

My jeep. 7* absolute.


His jeep. 27* absolute (actual angle that cardans see, accounting for pinion and tcase angles, is 17-18*)
 
#10 ·
You might want to check the condition of your transmission and motor mounts. Also check front drive shaft clearances between front of skid and exhaust header pipe.

I'm assuming you have disconnected your front drive shaft and driven it with it tied up to verify that it is actually coming from the front.
 
#12 ·
You might want to check the condition of your transmission and motor mounts. Also check front drive shaft clearances between front of skid and exhaust header pipe.
Mounts look good, no visible cracks. Clearances look good. (Had a front driveshaft hitting intermediate pipe after recent install on my jeep, so i know clearances there are fine)

I'm assuming you have disconnected your front drive shaft and driven it with it tied up to verify that it is actually coming from the front.
No i have not. Not after seeing the rear driveline angle. I'm gonna install this SYE & CV Driveshaft, set the proper pinion angle and test drive. If vibes are still present, i'll proceed from there. I ASSUMED it was front driveshaft because i was getting vibration feedback thru steering wheel.

Also, wheels and tires have maybe 1000 miles on them brand new. None of this even remotely existed prior
 
#17 ·
Pics wont do you much good right now. I will post some after she is all put back together.

The last alignment sheet reads 5.8 degrees caster. 5 is the recommended per Currie.

No SYE as its a Rubicon. The front is stock DS, the rear is a double CV.
 
#19 ·
Update:

Got the SYE in. Adams driveshaft in. Set pinion, then realized i'll have to reset because i don't have belly pan on because i'm doing fluid fill and tranny change in the AM (Couldn't get to local performance shop to get some Redline C+ and MT-90).

So just to be clear, i'm setting rear pinion to be essentially equal to driveshaft which means it's aimed at tcase output yoke? Or 1* difference down to allow for acceleration?
 
#20 ·
Update:

Got the SYE in. Adams driveshaft in. Set pinion, then realized i'll have to reset because i don't have belly pan on because i'm doing fluid fill and tranny change in the AM (Couldn't get to local performance shop to get some Redline C+ and MT-90).

So just to be clear, i'm setting rear pinion to be essentially equal to driveshaft which means it's aimed at tcase output yoke? Or 1* difference down to allow for acceleration?
I put mine back in on Weds and set mine 1-2 degrees below to allow for pinion climb during acceleration. Let us know how it goes!
 
#24 ·
yeah. still have some feedback. pretty consistent at pinion 1* up, even or 1* down. less feedback seems to be at 1* up (which comes out to 3.5 caster), but i could be imagining that its better when it's not. Might have to go 2* up.

800 miles on new tires, so it's not that. dry steering test looks good. Toe-in acceptable. Everything torqued correctly. Rear axle is off 1.5", that's my last obvious adjustment.

Sidenote: a nutsert is spinning on a skid plate bolt. it's against the frame so that's good. Gonna have to replace that tho...
 
#25 ·
Sorry about above post, didn't realize you were this far into it. Did you by chance isolate it to the front driveshaft? You never said whether you pulled the front shaft to check or not even though it was mentioned. The other thing I would check as it happened to a friend of mine, is make sure your pinion nuts are tight. Also check the output shafts on the t-case. His was WAY loose and couldn't figure out where the vibe was coming from.
 
#26 ·
I'll check front and rear pinion yoke nuts, and front driveshaft mounting bolts. T-case outputs are good, as I removed case completely for sye install. And yes, taking driveshaft out is in the next few steps.
 
#27 ·
#28 ·
That rotational movement is normal since those are ball joints inside. If they couldn't rotate like that, they'd snap when the axle moved up & down. I'd rather see if there's any movement at the passenger-side track bar mount when the steering wheel is turned left/right with the tires on the ground.
 
#30 ·
Laggy,

If you haven't pulled that front DS off yet and given the TJ a test drive to confirm that isn't it, imho I'd move that way up in the priorities of work. It is unusual that the OEM front CV DS (it is a CV after all) is the vibe cause after a lift (and rear CV install), but I'm living proof that it does occur. My particular vibe (40 mph and building as you go up) would disappear with the new rear CV DS removed and only running on the front DS. Gotta be the rear, right?

Hell no. After a couple weeks of working with my local Vegas smart guys, we took out the front DS just to confirm and it ended up that it was the culprit (new angles after lift exacerbated whatever was worn in her). Rebuilt the front DS and no more issue. And why did the vibes disappear when the rear CV was removed? Front would not duplicate the vibes when it had a load on it is the best we can ascertain...

Since it is easy to remove the front (and more importantly doesn't cost any $$), I'd work that higher into your isolation troubleshooting.

And most importantly? Good luck. Isolating vibes does suck.
 
#31 ·
^^^ Thanks for the info brother ^^^

Looks like I'll pull it. I've been driving it around tonight and 90% of the vibes are gone. I realized, after driving my jeep around northern AZ this weekend, that vibes can be transmitted thru the jeep from crappy roads. This may seem obvious. But when going thru a jeep suspension you always gotta wonder.
 
#32 ·
Removed front driveshaft. Vibes still the same. Noted with and without DS that the vibes are under accel. I'll readjust rear pinion angle, as of right now it's 1* down. I'd be surprised if that's causing it, but then again i'm a noob in the ds department. Also thinking it could be motor mounts, even though visually they look good. Maybe i'll sell him my 6 month old Brown Dogs for $50 since i want the 1" MML version (didn't realize with my 1" body lift that i needed them).

Anyway, the scientist in me says to run without new Adams rear cv ds, although i think that's probably a waste of time.
 
#36 ·
So owner took jeep back today. He's beyond stoked. He said nothing seems different in vibrations. After getting the bad vibes to go away, I was overthinking it. Pinion 1° up, 0, 1° down netted no noticeable difference. Roads are pretty bad in Phoenix and I was test driving the same stretch of road, didn't even think to change route.

He says the jeep pulls slightly to left. I centered the steering wheel with drag link but it's a touch off right. So when he centers, it pulls lol. Wheels seem to return to center well. I think I'm gonna get 1° more caster and put front pinion at 0 relative to driveshaft (it's 1° up right now). Should technically help road manners and now I know it won't make more vibes.

I learned A LOT. Probably spent equal time researching and actually doing work on the jeep. God knows how much dirt is on my PC keyboard lol
 
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