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Vibrations > 45 MPH... Close to Fix?

rmoorex

NAXJA Forum User
Location
Indiana
1991 Two Door, 5 Speed, 3 inch lift. All drive-line components, steering components, suspension, track bar, control arms, etc have less than 3,000 miles. Totally new/rebuilt front Dana 30 front, 44 rear.

SYE with new Tom Wood's double cardigan front and rear propeller shafts.

At 45 MPH plus, mean vibration. Constant and distinct.

Until last night.

This is round II.

First tried a 1" T-Case drop based upon recommendation from several people. Then did my own research. Learned that A) a t-case drop is more or less a potential solution that is just luck-of-the draw; B) t-case drop can result in accelerated motor-mount damage.

Called Tom Woods. A tech told me about the need for a double cardigan to be within 1 degree of pinion angle on the axle side.

Measured. Did a 7 degree shim install.

Now, with each imperfection in the road, the vibration "stops" for a brief moment. Each pot hole, rail road tracks, less than smooth road surfaces.

Upon research, axle assembly and/or propeller shaft angle will flex 1 or 2 degrees when a vehicle "encounters" uneven surfaces.

Could it be that I am within 1 or 2 degrees of being in-range?

Also, maybe I am measuring wrong? I measured on top of the "collar" on the Dana 44 and on top of the rear propeller shaft. Right now both angles match. Makes me think that I am placing the angle finder in the wrong place on the Dana 44.

Hope that a patron can provide more insight.
 
You should be placing your angle finder on the back of the diff and on the driveshaft itself.
 
I thought that I heard/read, "Place the angle finder on the 'service area'."

Next to the fill plug?

Angle from "the back of the diff" + angle on the propeller shaft should = 90 degrees?
 
If you have an SYE installed, then there is no reason for transfer case drop spacers.

The angle finder is placed on a machined flat surface of the differential housing casting. Typically the machined surface where the diff cover is to be installed, or the pinion snout.

The rule thumb for shimming an SYE is about 1° of shim per inch of lift. I would say you have too much shim installed.
 
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Also remember that a 2* shim will make a net change of about 3*.
 
The comments about pinion angle are spot on. Also, don't ignore the possibility that the new driveshaft is out of balance.
 
Your driveshafts (front and rear) should look like this:

cv_angle.gif


(Image stolen from: http://www.4xshaft.com/driveline101.asp)

If they don't, you're going to have driveline vibes.
 
Yup changing the pinion will have an effect on the driveshaft as well. If you have a 6 degree difference I would start with a 4 degree shim and recheck the angle, for example.

Thanks to everyone for the info/input!

Put in a 4 degree shim. Worse. Far worse.

When I had the 7 degree in, I placed the angle finder on the top of the snout of the centersection (also called the pumpkin) and on top of the drive shaft. In both cases the angle matched. Have photos. But I guess I cannot post those here.

Now it looks like things are 2 - 3 degrees off.

Pulled the rear drive shaft all together. Smooth as silk up to 55 MPH.

With the rear propeller shaft in, things start shaking at 45 MPH.

Discouraged for sure.

Last ditch effort before I take it to a shop is to send the shaft back to Tom Woods for recheck on the balance. They advised that driving with the angle off, and "exposing" the thing to so much vibration, the shaft could be damaged/out of balance.

Possible, I don't know.

This all started when installing the SYE and the Tom Woods custom shaft.

Crossing my fingers.
 
7° vibes, 4° vibes. No drive shaft - no vibes, kinda makes one suspect the driveshaft.

Simple test of above theory, install the front driveshaft on the rear axle.
 
Vibrations > 45 MPH... Close to Fix?

Send the driveshaft back to tom woods for re balancing - it’s free and then you will know if that’s it or not


Sent from my iPhone using Tapatalk
 
7° vibes, 4° vibes. No drive shaft - no vibes, kinda makes one suspect the driveshaft.

Simple test of above theory, install the front driveshaft on the rear axle.

Moved the front to the rear as advised. Same result. Vibes @ 45 and higher.

Waiting for a SYE yoke to arrive. Tom Wood's advised that maybe the yoke is out of wack. Will see.
 
What SYE kit did you buy?
 
That could easily be the problem if it is one of the chinese units.
 
Moved the front to the rear as advised. Same result. Vibes @ 45 and higher.


Crown SYE kit.


Cheap crappy Chinese clone parts are always suspect. Everything from Crown Automotive and Omix-Ada I have bought for my CJ-7 and XJ's has either fit poorly, worn out quickly, or done both at once.
 
I recall seeing a video on Xj drive shafts and making sure that if the 2 sections are separated they have to go back together the way they came from the mfr. They are stamped. Could be a simple fix, good luck
 
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