OME Spring Lift and Pinion Angles

[SAString]

Adding new Bilstein shocks and OME springs was the first investment I made in my '02 KJ Sport. Everything had aged and sagged below the recommended 19" overall height, so it was time.

I followed all the recommendations of the members and decided on Bilstein 4600 shocks, with OME 927 springs in the front and 948s in the rear. The ride is AWESOME! Big improvement. Ride height is higher with 20" in the front and 21 3/4" in the rear. But, now I have driveline vibrations I cannot solve. I've come to the conclusion it's the pinion angle caused by the uneven ride height.

Many have posted that they don't have vibe issues after lifting, but I suspect the lifts are equal, front and rear, so as not to change the driveshaft geometry. Thoughts?

Before having my springs cut, I thought I would experiment with adding weight to the rear (sandbags) until I match the front height. If the vibes are gone, I've found my issue.

Are there ways of lowering the rear height besides cutting springs? Help appreciated.
Thanks

 

[tommudd]

Adding new Bilstein shocks and OME springs was the first investment I made in my '02 KJ Sport. Everything had aged and sagged below the recommended 19" overall height, so it was time.

I followed all the recommendations of the members and decided on Bilstein 4600 shocks, with OME 927 springs in the front and 948s in the rear. The ride is AWESOME! Big improvement. Ride height is higher with 20" in the front and 21 3/4" in the rear. But, now I have driveline vibrations I cannot solve. I've come to the conclusion it's the pinion angle caused by the uneven ride height.

Many have posted that they don't have vibe issues after lifting, but I suspect the lifts are equal, front and rear, so as not to change the driveshaft geometry. Thoughts?

Before having my springs cut, I thought I would experiment with adding weight to the rear (sandbags) until I match the front height. If the vibes are gone, I've found my issue.

Are there ways of lowering the rear height besides cutting springs? Help appreciated.
Thanks

Only 20 inches if front ???
Should be at 21.5 at least in front
Are you sure you received 927s in front ?
I would never even think about cutting the springs, will never set right

 

[Aceofspades]

JBA sells strut mount plates and Clevis spacers to raise the front

 

[JasonJ]

Cutting springs is by far the absolute worst way to address this. This isn't 1996 Tuner Warz where cutting springs to lower your Honda Civic HX is "the thing to do". Bud, that'll cause a world of pain for you if you approach it like that.

Tom is right, 927/948 springs should put you well above 20" in front. 20" is only 1/2"-1" max over stock ride height... OME 947's will give +2.5".

You're probably spot on about the vibrations, but I'd address the reason why your front is not correct first. After that, JBA makes a bracket that allows you to rotate the rear axle forwards to re-align the pinion.

 

[SAString]

Thanks All. Sorry about my stupid mistake with all the numbers. I have OME 2926 springs in front and 2947 in the back. I re-measured and I'm a solid 21" in the front (from center of the hub straight up to bottom of the plastic fender radius). Measuring the same way, I'm slightly >22" in the back.

Since I don't want to raise the front any higher, it sounds like the JBA bracket would be my next step? It seems if the TC output is pointing up (towards the higher rear) that the diff should point down to make them parallel. Am I thinking correctly?

Also, I always wanted to know if I need that big "harmonic balancer" disc near my front spline/UJoint. Is that necessary??? I just seems like something else to throw off the shaft balance. These vibrations are driving me mad!

 

[JasonJ]

Thanks All. Sorry about my stupid mistake with all the numbers. I have OME 2926 springs in front and 2947 in the back. I re-measured and I'm a solid 21" in the front (from center of the hub straight up to bottom of the plastic fender radius). Measuring the same way, I'm slightly >22" in the back.

Since I don't want to raise the front any higher, it sounds like the JBA bracket would be my next step? It seems if the TC output is pointing up (towards the higher rear) that the diff should point down to make them parallel. Am I thinking correctly?

Also, I always wanted to know if I need that big "harmonic balancer" disc near my front spline/UJoint. Is that necessary??? I just seems like something else to throw off the shaft balance. These vibrations are driving me mad!

That "harmonic balancer" disc is there for a reason, don't remove it. If you think driveline vibrations are bad now... it's there to maintain shaft balance, not throw it off. Meh, who needs wheel weights too? lol, j/k,m just poking fun bud. Nah, leave it alone.

The two ends of the driveshaft ideally wouldn't point up nor down.. but straight out, but that rarely happens. Just like in the picture in your post, if the tc is pointing up, you need to rotate the rear diff down, rotating the rear axially towards the front of the vehicle achieves this. Then, parallel outputs are more in line and you should be good to go, if that is the source of your problems to begin with.

 

[SAString]

That "harmonic balancer" disc is there for a reason, don't remove it. If you think driveline vibrations are bad now... it's there to maintain shaft balance, not throw it off. Meh, who needs wheel weights too? lol, j/k,m just poking fun bud. Nah, leave it alone.

The two ends of the driveshaft ideally wouldn't point up nor down.. but straight out, but that rarely happens. Just like in the picture in your post, if the tc is pointing up, you need to rotate the rear diff down, rotating the rear axially towards the front of the vehicle achieves this. Then, parallel outputs are more in line and you should be good to go, if that is the source of your problems to begin with.

Thanks JasonJ: I need a good poke now and then Good answer! Good to know you looked at my picture, understand the issue and provided concurrence of my thinking. I've replaced and balanced everything that could be causing vibrations (except the transfer case), so this adjustment may be just the ticket. (It can't hurt....only my wallet). Will the JBA website explain the item that I need?

 

[Aceofspades]

Y link extension bracket JBA

 

[tommudd]

Y link extension bracket JBA

Not really that high to need one really
Installed a lot much higher and no drive line vibes afterwards.
Have you checked the ujoints yet ? A lot of time there is your issue
Seen them froze solid almost , change angle and then vibes start

 

[SAString]

Not really that high to need one really
Installed a lot much higher and no drive line vibes afterwards.
Have you checked the ujoints yet ? A lot of time there is your issue
Seen them froze solid almost , change angle and then vibes start

Thanks Tom: Back in January, I installed new Moog greased U-joints prior to the shop balancing the shaft. Test drive= Still vibrates at 50. The shop said I should be using sealed UJoints, because they have tighter tolerances. In May, I pulled the shaft, greased the splines and pressed-in new sealed UJoints. Test drive= Still vibrates at 50. Frustrating. I've replaced everything in the front except the diff. The only things left are the transmission, transfer case, and Pinion angle. I don't know what else it could be.

 

[Myke]

Pull the rear shaft. Put it in 4wd and go for a test drive. Then you'll know for sure if it's your driveline angles or something else.

 

[SAString]

Pull the rear shaft. Put it in 4wd and go for a test drive. Then you'll know for sure if it's your driveline angles or something else.

Thanks Myke: I'll give that a try this week. It only takes 15 minutes to prep and pull the shaft. I just need to find the 15 minutes! Guests at the house all week, etc.. I'll get back on here and post my findings. I appreciate everyone's advice.

 

[SAString]

Pulled the rear shaft

Last night I pulled the rear shaft, put it in 4wheel high and drove at highway speeds. Things were a bit quieter but, lo and behold, the bad vibration is still there! Definitely coming from the front.

I have another thread going about my intermediate shaft not having a clip at the CV axle spline interface. 4Wheel Parts has ordered me a new Intermediate shaft (with clips) and CV axle and has agreed to replace them free of charge. Those spines are self-destructing without the clip and I'm sure that is a source of vibration.

While I had the shaft out, I pressed in new Spicer U-Joints. Drove this morning and the front vibes are over shadowing any vibration coming from the coming from rear shaft and pinion angle. While 4WP is replacing the shaft and axle, I'll have them check the pinion angle and we'll decide what to do next..

 

[SAString]

OK, 4WP replaced the front Passenger CV axle and Mid shaft for free. It still vibrates. They're baffled also. Told me to have a second look at balancing the rear shaft. It seems I'm going over everything twice.

 

[u2slow]

Have the bushings/bearings in the ends of the front diff housing been renewed? How old/worn are the front unit bearings?

The KJs with the NP241J don't have a damper ring on the driveshaft. Not sure when or why it is required on other cases.

FWIW, the rear tri-link extension bracket isn't really needed until you're tall enough that you're tearing up UCA bushings repeatedly. The 3/8" bracket thickness raises the pinion up even with zero shims. May be good for a CV style shaft, but makes for unequal ujoint angles otherwise.

 

[Myke]

FYI you can't adjust the front pinion angle on an IFS vehicle. Lifting it does not affect the front pinion angle nor does having an uneven ride height.

I would check the easiest things first working down to the more difficult parts.

balljoints > unitbearings > front shaft t-case side cv joint > can skip checking your axles since they were replaced twice > diff housing bushings > pinion bearing > carrier bearings

 

[SAString]

FYI you can't adjust the front pinion angle on an IFS vehicle. Lifting it does not affect the front pinion angle nor does having an uneven ride height.

I would check the easiest things first working down to the more difficult parts.

balljoints > unitbearings > front shaft t-case side cv joint > can skip checking your axles since they were replaced twice > diff housing bushings > pinion bearing > carrier bearings

Thanks Myke:
I bought the Y-link several weeks ago with a set of new JBA front A-arms. I need to double check the spline angles, but last I recall they were a few degrees different. If the Y-link can get them exactly the same, then I can rule that out. For your other recommendations:
balljoints > Uppers and lowers replaced with JBA and Moog
unitbearings > I'm unclear on what these are. Can you provide a location for me?
Front shaft t-case side cv joint > Vibes still occur without the front shaft installed.
diff housing bushings > I'm unclear on where these are. Can you provide a location for me?
pinion bearing > I'm unclear on where these these are. is this out of the transfer case?
carrier bearings > I'm unclear on what these are. Can you provide a location for me?

 

[u2slow]

The JBA Y-link bracket doesn't help pinion angle. What it does is keep the upper arm closer to level (when lifted) so it doesn't strain/tear the upper control arm bushings as easily.

unitbearings > I'm unclear on what these are. Can you provide a location for me?
Front shaft t-case side cv joint > Vibes still occur without the front shaft installed.
diff housing bushings > I'm unclear on where these are. Can you provide a location for me?
pinion bearing > I'm unclear on where these these are. is this out of the transfer case?
carrier bearings > I'm unclear on what these are. Can you provide a location for me?

unit bearings > the front wheel bearing/hub... wheelstuds are mounted in them

diff housing bushing > in the ends of the aluminum front axle housing; supports the inner end of the CV axles

pinion bearings > slip/press fit on the pinion gear, inside the diffs, behind the yoke

carrier bearing > inside the f & r diffs, supports the axis the ring gear turns on

 

[SAString]

The JBA Y-link bracket doesn't help pinion angle. What it does is keep the upper arm closer to level (when lifted) so it doesn't strain/tear the upper control arm bushings as easily.



unit bearings > the front wheel bearing/hub... wheelstuds are mounted in them

diff housing bushing > in the ends of the aluminum front axle housing; supports the inner end of the CV axles

pinion bearings > slip/press fit on the pinion gear, inside the diffs, behind the yoke

carrier bearing > inside the f & r diffs, supports the axis the ring gear turns on

Thank you U2Slow ! Since I've been all over this KJ replacing and balancing the "low hanging fruit" to solve the vibration, these "Internal" areas are going to be much more challenging. It could be one bearing our a combination. I'm driving with the front shaft out to help me zero in. The vibes get bad around 50, only when applying gas, especially when going uphill. Coasting- smooth and barely noticeable.

Any ideas where I should start? Based on the list, maybe rear pinion bearing?

 

[u2slow]

Worn pinion bearings normally make noise all the time... maybe changing pitch with speed. Not vibrate at a specific speed.

I would re-check the rear shaft... ujoint angles, slip spline, how much does the pinion rotate upward under load? I'd even try remove the shaft for a quick spin (4Hi) to see if it goes away.