Slight vibration. Looking for help.

T

Team Desert Eagle

New member
I recently put on a coast front driveshaft and it feels like I have a slight vibration that can only be felt in the gas pedal. 4.5" lift 35" tires. 08 with auto transmission. Front pinion is up 2.5 degrees from level. Driveshaft is coming down at about an 8.5 degrees. Drivability seems ok with the caster being at about 3.5.
Anyone have any ideas or am I just worried for nothing??
 
wayoflife

wayoflife

Administrator
Staff member
Are you 100% sure about your caster angle? Take a reading at the front of your diff by placing an angle finder over the flat surface of the case spreader hole. It should read 0° or there about. If not, you may still have too much positive caster.
 
T

Team Desert Eagle

New member
The angle finder did read 0 degrees then I adjusted the upper control arms to bring up the angle to 2.5 degrees assuming that this would help the u joint angle.


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T

Team Desert Eagle

New member
Maybe I should have left it at 0 degrees but I thought that there was too much angle in that front u joint at 8.5 degrees. After I raised the pinion I assumed that the 6 degree difference in that joint would help, but I might be wrong.
Do you think it would be beneficial to lower that back to 0 degrees and see if I still have vibes?


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wayoflife

wayoflife

Administrator
Staff member
Well, if you're really getting a 2.5° reading on the front of your diff with the pinion up, that should have made things even better but at the cost of handling. Are you sure that the vibrations are coming from your front shaft? Did you try pulling it to make sure?
 
T

Team Desert Eagle

New member
I lowered the pinion to 1.5 degrees and the driveshaft now reads 7.5 degrees (odd). Took it out and drive it. Feels like vibration is almost gone now. It is strange, I would have thought that vibes would have increased.
I did take the shaft out last week and could not feel the vibes.
I talked to Northridge 4x4 where I bought the shaft and they explained that these vibes might be the fact that there is more rotational mass in the new shaft.
These vibes are so slight that they are almost un noticeable but I might just be paranoid with all the t case failures that I have read about.


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wayoflife

wayoflife

Administrator
Staff member
Is there a chance that you've gotten things confused and have been adding more positive caster than less in the past. If the vibes are almost gone, I might try adding a tad more and see if they disappear altogether. I like Northridge but what they told you is bunk. A well balanced drive shaft installed with the proper amount of caster shouldn't have any vibrations.
 
jeeeep

jeeeep

Hooked
I installed a coast front ds and no vibrations -but I did make sure to account for the slope of my driveway to get an accurate read.

is your jeep on a flat surface? this might be throwing your read off.
 
T

Team Desert Eagle

New member
My jeep is sitting in my garage with no slope at all. I can send pics of the angle finder an the axle if need be. When the lift was originally installed the pinion angle was at 0 degrees. After I noticed the grease flinging out I added the adjustable upper control arms in preparation for the new shaft,to get more length in the arms and roll the pinion angle up. Today I shortened the arms by two full turns each which dropped my angle back to 1.5 degrees. After a short drive in the highway the slight vibes that I felt before seemed to be almost gone. I don't feel vibes in the gas pedal anymore but with my left foot flat on the floorboard I can feel the slightest vibe, almost like knobby tire type vibe.
I plan on taking the shaft out in a few months and getting it balanced and checked out while the jeep sits in the garage for the long Michigan winter anyway.


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