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Unread 11-18-2007, 05:49 PM   #1
webqaz
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Symptoms of bad pinion angle?

I have been trying to track down a vibration problem. When the pinion angle is off what symptoms do you generally, have. I know you can measure the angle. I am currently having a problem where I get a small vibration and a loud lower tone hum when I drive around 70mph. When I drive faster it appears as though the hum gets louder but does not change much in frequency. It almost seems like the sound is coming from the transfer case area but I am still trying to track it down. The hum goes away when I take my foot off the gas. I have a 1999 XJ with a 3.5 RE AAL lift kit, and SYE. The problem started occurring when I first put the lift on. I have tried both 4 degree and 6 degree shims. With the 4 degree shims the hum appeared to occur at a lower speed (around 60mph). I am just trying to figure out if when the pinion angle is off if you get a hum like this? Any ideas guys?

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Unread 11-19-2007, 03:44 PM   #2
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Bump

Bump..................
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Unread 11-19-2007, 04:27 PM   #3
Wheelin98TJ
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Other than measuring, you can remove the rear driveshaft and go for a ride.

If the vibration is gone, there's your problem. Its either a bad u-joint or the pinion angle is off.
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Unread 11-19-2007, 04:51 PM   #4
webqaz
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Im ruling out that the u joint is bad because the DS was brand new. I also tryed using the front shaft on the rear and still had the vibration. The 6 degree shim measures too high by about 2.5 degrees but the vibration occurs at around 70mph. But when I had the 4 degree shims the vibration occurred around 65mph. If the pinion angle is the problem do you usually get a loud low hum and just a small vibration? For some reason I am almost suspecting something from the SYE installation, I dont know.
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Unread 11-20-2007, 05:39 AM   #5
mdm
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Quote:
Originally Posted by webqaz
Im ruling out that the u joint is bad because the DS was brand new...
Don't overlook "new" parts when trying to determine the source of a problem. New parts can be defective, installed incorrectly, not lubed properly,...
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Unread 11-20-2007, 09:59 AM   #6
webqaz
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I also used the front DS in the rear and the sound was still there. It is probably not tires because I have tried three different good sets on the vehicle. I did have an alignment done on it after the lift was installed and I had the hum. It didnt really affect things too much. I wonder if I should have the front end aligned again. I am also suspecting maybe a bad wheel bearing or something like that. It just seems weird though if it was a bad bearing why it would show up right after the lift was installed.
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Unread 11-20-2007, 10:01 AM   #7
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I guess there is also a possibility that it could be something with the SYE installed but I have not heard of many people having problems with theirs.
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Unread 11-21-2007, 05:20 PM   #8
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I guess my question is after I put on a lift and the jeep then started a roaring sound at highway speeds is that an indication of in proper pinion angle? I have measured the angle but 4 degrees seemed a little low and it looks like 6 degrees is a little high.
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Unread 11-21-2007, 10:59 PM   #9
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Could be anything. As above completely remove the rear driveshaft and see if the problem is still there. Swapping another part in place and going for a test drive isn't going to eliminate the rear end as a source. That's going to run you around in circles and you'll still need to troubleshoot. Until you've eliminated 1 potential as a problem you don't know whether or not to move forward.
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