Got SYE and still got vibs

[xjdavid1]

I have just fitted a 4.5"RE kit, MIT SYE and double cardin drive shaft. The back is a 6" and the front is 5.5". I still have vibes. I have removed the front drive shaft and the vibes are still there. Should I be getting vibes at this height. The only thing I can think of is the rear drive shaft is not balanced properly. I set the pinion angle at 0 with 220 lb in the back as I figure it will settle a bit and I will mostly be carring some camping gear. The vibes are the worst around 40mph and are bad enough to make the dash and centre console shake. Any ideas??

 

[JLane99XJ]

I set the pinion angle at 0 with 220 lb in the back as I figure it will settle a bit and I will mostly be carring some camping gear. The vibes are the worst around 40mph and are bad enough to make the dash and centre console shake. Any ideas??

maybe at that mph the torque load is just enough to wrap the spring slightly and cause the pinion to rotate upward making the angle obtuse causing an imbalance,
if you're using degree shims then swap for some less degreed by 2* or if you rotated the perches and fully welded them try running some 2* shims to bring the pinion down a fuzzzz

 

[Dirk Pitt]

I have just fitted a 4.5"RE kit, MIT SYE and double cardin drive shaft. The back is a 6" and the front is 5.5". I still have vibes. I have removed the front drive shaft and the vibes are still there. Should I be getting vibes at this height. The only thing I can think of is the rear drive shaft is not balanced properly. I set the pinion angle at 0 with 220 lb in the back as I figure it will settle a bit and I will mostly be carring some camping gear. The vibes are the worst around 40mph and are bad enough to make the dash and centre console shake. Any ideas??

When you say you set the pinion angle to zero, do you mean referenced from the ground or the front driveshaft.

With a SYE, the pinion should point directly at the t-case output, or 1-2 degrees below it.

HTH

 

[fordtech]

sounds like you didnt set your angles properly to me.....an sye and/or a cv shaft alone does not fix vibes, there is some adjustments to be made.

 

[xjdavid1]

I set the angle of the bottom u joint at 0 degrees. I will try turning the diff down a couple of degrees. So I take it that I dont need to lower the transfer case at all.

 

[Jeepin Jason]

zero degrees relative to what though? sounds like relative to the driveshaft from what you are saying.

Also, check the length of your new rear driveshaft against your front driveshaft. Depending on which transmission you've got, with that much lift the front and rear driveshafts may be interchangeable. Assuming the MIT SYE uses a yoke and not a flange. If the driveshaft lengths are comparable, you might swap the front shaft into the back and see if that makes any difference in the vibs.

 

[xjdavid1]

The vibration is still there when I backoff the accelerator and doesnt get any worse when I accelerate. I am inclined to think it is not angle related. Havent tried shimming the diff yet. Yes angle is in relation to driveshaft.

 

[Meeks]

Well-- I would try lowering the angle before anything.

 

[xjdavid1]

you mean lower the transfercase

 

[JLane99XJ]

you mean lower the transfercase

no.. that would make the angle obtuse like i was talkin about with axle wrapping.

lower the pinion angle...

 

[xjdavid1]

I just measured the angle on the double cardin and it is 12 degrees. Sounds way to much to me. What does everybody else think is the maximum angle for no vibrations.

 

[PETEY]

The vibration is still there when I backoff the accelerator and doesnt get any worse when I accelerate. I am inclined to think it is not angle related. Havent tried shimming the diff yet. Yes angle is in relation to driveshaft.

that is the problem then. you did not shim your axle.
http://www.4xshaft.com/
click on "tech info" at the top, then click on "geometry 101"

 

[Gojeep]

David, put a angle finder on the back of the diff housing where the diff spreaders fit in, ( flat area each side of the cover with a recessed hole in it ). That angle should be 87-88* different to what it reads when you place the angle finder on your driveshaft.

 

[Kuasimodem]

Are you sure it's a driveline vibration and not a bad balance job on your tires/rims?

My 92 would shake pretty bad between 40 and 60 after I had new tires put on, and having the tires rebalanced fixed the problem.

Try taking your Jeep back to where you got the tires mounted and balanced and have them recheck the balance without removing any of the weights.

 

[xjdavid1]

I have had 2 sets of tyres and same vibes. Driveshaft going back to get rebalanced tomorrow.

 

[XJSpencer]

If you can, take the whole Jeep to the Driveline shop. They can check everything visually. My Jeep needed the pinion to come down and the shaft was out of balance. I also had a bad joint. If you don't have manual hubs in front, You should have him do the front shaft also. I have the H+T also.

Free advice is worth what you pay for it.

Mine is smooth to about 80 mph. That's as fast as I've had it.

 

[xjhm]

The angle is not hard to set, but if you have never done it before it may be confusing....but sounds like the angle is off ...set the angle at the pinion just below the centerline of the shaft...oh and when you install a 3' shim, that doesn't always mean you will have a 3' movement in your angle, the shims can be right on or way off depending on type/manufacturer...

 

[xjdavid1]

I have just put in a 44 out of a TJ and I welded on the spring perches with 0 degrees on the bottom uni or 0 degrees between the diff pinion and the drive shaft as per the text book. I used a couple of steel rules and a plumb bob to do this. It seemed to be quiet accurate. Drive shaft goes in today to be checked. Not easy to get the whole car in there yet but that will be next I suppose.

 

[xjdavid1]

Problem solved. Got DS back from the shop today and they have moved the weights 90 degrees. I think the bloke must of went to sleep the first time he balanced it.

 

[Gojeep]

Glad it was something so simple in the end. Dont know why he didn't test run it again after the weights were added to make sure it was perfect which is normal practice?