2.5" lift installed, now have a vibration

wm69

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
God's Country
State
AR
#1
Well, finally got the extra axles under my hunting Jeep. 2.5" Rancho springs with new shocks, and locked stock axles with 3.31's

The ubolts came with aluminum shims for the springs, which I knew not to use, and after reading that with a 2.5" lift that shims usually weren't necessary, I opted to try things without shims.

http://www.cj-8.com/forum/showthread.php?43919-Epic-fails&p=351283#post351283

Of course, as was pointed out in the above post, I get a nice vibration now when driving down the road.

If I push the clutch in and coast, everything is smooth as silk. Under power I start getting vibes which get pretty bad at about 35-40. I assume this means I need to shim the rear springs, and I know I should get steel shims and not use the crap aluminum ones that Rancho supplied.

So how does one figure out what degree of shim to use? To add to the irritation, I'm gonna have to get longer spring centering pins to go through the shim. Are those standard bolts or is it some specialty part?
 

AK-RWC

Legacy Registered User
SOA Member
City
south central
State
AK
#2
I had to go through this with my CJ-7. To make matters worse, my dad had already installed longer rear shackles with a shim eons ago before he gave it to me. When I put on my 2.5" lift springs, it got complicated.

I picked up a magnetic angle finder so I could measure the transfercase yoke angle, and then ordered a steel shim that would theoretically match. Yes, you need longer centering pins; my local NAPA carries them, but I had to find the guy that knew what I was talking about and where to look for them.

Even after I did that, I still had a vibration, so I gave in and got a double-cardan shaft.
 

wm69

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
God's Country
State
AR
#3
I had to go through this with my CJ-7. To make matters worse, my dad had already installed longer rear shackles with a shim eons ago before he gave it to me. When I put on my 2.5" lift springs, it got complicated.

I picked up a magnetic angle finder so I could measure the transfercase yoke angle, and then ordered a steel shim that would theoretically match. Yes, you need longer centering pins; my local NAPA carries them, but I had to find the guy that knew what I was talking about and where to look for them.

Even after I did that, I still had a vibration, so I gave in and got a double-cardan shaft.
Not exactly filling me with confidence here!

I had longer shackles on this Jeep for years. They were heavy with a crosspiece welded in, and had two different sets of holes drilled for different height settings. I reused them, but moved the bolt to the inner hole and cut off the excess so they're just a hair over stock length now.

So trying to visualize this.

Get one of these http://www.sears.com/craftsman-magn...p-00939840000P?prdNo=1&blockNo=1&blockType=G1

Set it on the transfer case yoke, get the angle. Set it on the pinion yoke, get the angle, then if say the transfer case is 0 and the pinion yoke is 3 I would need a three degree shim to equalize the measurement?
 

AK-RWC

Legacy Registered User
SOA Member
City
south central
State
AK
#4
Set it on the transfer case yoke, get the angle. Set it on the pinion yoke, get the angle, then if say the transfer case is 0 and the pinion yoke is 3 I would need a three degree shim to equalize the measurement?
That's the theory. And if that doesn't work, then you end up like me, shimming it to point directly at the t-case and running a double-cardan shaft.
 

BRKLYNZ28

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
BROOKLYN
State
NY
#5
Yep and then you get a woody.. "Tom woods shaft" 😉

Sent from my SM-N910P
 

LetchcoreCJ7

Legacy Registered User
City
Nashville
State
TN
#6
I have never had any vibration out of a 2.5in lifts. I do think I have used a shim in the rear every time though. I also do a 2 deg shim in the front now too.

What made you go with Rancho springs?
 

wm69

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
God's Country
State
AR
#7
I have never had any vibration out of a 2.5in lifts. I do think I have used a shim in the rear every time though. I also do a 2 deg shim in the front now too.

What made you go with Rancho springs?
Picked them up used several years ago. At the time Rancho was still making them, but I think they discontinued the CJ lifts now.

Anyhow, saw a used set of Rancho lift springs for $100, snapped them up. Seller took them off to go bigger.

Like most of my projects, they've been sitting in the shop for years, and I'm just now putting them in.

They don't ride great, but are better than my worn out factory springs with long shackles, and this is a hunting rig so doesn't see a tremendous amount of road use anyway.
 

AK-RWC

Legacy Registered User
SOA Member
City
south central
State
AK
#8
If you end up needing a shaft, check out Adams Driveshaft. I've picked up f/r shafts for my wife's ZJ from them and have been very pleased with price and service.
 
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