Pulsating vibration

bfnc27201

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Feb 20, 2018
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North Carolina
4 in suspension lift running 33x12.50x15s. When I bought Jeep it had a slight vibration between 60-65mph that you felt in the steering wheel slightly. Cupped tire on front passenger side was found to be the culprit. Ended up moving that tire to the rear as my spare was cupped as well. Moving it to rear reduced steering wheel vibration but obviously moved a slight vibration to the rear.
I ended up finding a Dana 44 with disc brakes and opted to grab it before replacing the tires. Replaced front and rear rotors, calipers, and shocks. Had Dana 44 installed, SYE, Adams driveshaft and adjustable control arms in the rear and had transfer case lifted back up.
The shop found a busted tranny mount and replaced this as well.
Leaving the shop I had what I described as a pulsating vibration very faintly felt in the seat. At 45-50mph it would last for 2-3 seconds and reoccur every 5 seconds. No other vibrations at lower speeds or highway speeds.
The pinion angle was found to not be set correctly and they readjusted. I Left the shop and the vibration was less frequent but now at 70mph there was a vibration that is constant. So, I decided that knowing my tires were in need of replacement I’d bite the bullet and replace them. Was hoping to run the other tires for awhile even though they had some issues.
Now, Brand new tires, and the issue is still there.
There is no death wobble, no weird noises, Jeep rides really smooth and maybe I’m being anal about it but I know what I’m feeling in the seat that was never there before.
For what it’s worth, my shifter used to rock back and forth when hitting a bump, the 4wheel lever would rattle at low speeds and it was occasionally hard to shift, since the transfer case was lifted and the mount replaced everything is tight, doesn’t rattle, and Jeep has never shifted so smooth.
I’m at a loss. The shop has been more than helpful but something still isn’t quite right.
I still believe it’s in the driveshaft angle personally. None of this was an issue with the 35 installed.

In summary, 40-45 mph there’s a 2-3 second faint vibration followed by 5-10 seconds of no vibration. 70mph on the dot vibration is constant and feels like it’s all in the rear of the Jeep.
 
A pulsating vibration like that is normally a driveshaft vibration resulting from incorrect pinion angle, or possibly a bad U joint. First you need to isolate whether it's coming from the front or rear by disconnecting the front DS and driving the Jeep and seeing if it's still there or has it gone away? If it's still there, then remove the rear DS, put in 4HI and drive it . If it's gone away, then you know it's the rear DS. Which ever one it is, look at pinion angle and U joints.
 
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Check front pinion angle as well. Moving t case back up may have been enough to cause some issues in the front.
If that doesnt work try removing each shaft one at a time and driving to see if vibs go away. That can pin point which may be the culprit.
 
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A pulsating vibration like that is normally a driveshaft vibration resulting from incorrect pinion angle, or possibly a bad U joint. First you need to isolate whether it's coming from the front or rear by disconnecting the front DS and driving the Jeep and seeing if it's still there or has it gone away? If it's still there, then remove the rear DS, put in 4HI and drive it . If it's gone away, then you know it's the rear DS. Which ever one it is, look at pinion angle and U joints.
Yep, this my next step. I’ve had the shop look at and they say it’s right.
I had them do most of the work as I am very limited on my time with my work schedule. I guess I’m going to track it down myself.
They’ve been more than helpful but running it up and down the road to them is not an option.
 
Like mentioned above, pull the front ds, then the rear. Isolate which end it's coming from. I'm very familiar with the harmonics you are mentioning.
It was not there before the Dana 44 swap and the other work. I’m certain it’s something minor but it is irritating to say the least. It’s not my daily driver, only a weekend road trip vehicle, few trails, beach rides, etc.
 
Well, the SYE/DCDS is a pretty big change in itself. Chances are your tc output had a harmonic balancer, and when doing a SYE, that balancer can no longer be used. These TJ's seem to be really sensitive to change. Some do ok, others go wacko at the smallest change. Harmonic frequencies have a lot to do with it. Double check your rear pinion angle and make sure it is in line with or 1* lower than the ds angle. front ds needs to be close as well.
 
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Well, the SYE/DCDS is a pretty big change in itself. Chances are your tc output had a harmonic balancer, and when doing a SYE, that balancer can no longer be used. These TJ's seem to be really sensitive to change. Some do ok, others go wacko at the smallest change. Harmonic frequencies have a lot to do with it. Double check your rear pinion angle and make sure it is in line with or 1* lower than the ds angle. front ds needs to be close as well.
Was 7* out when I picked it up from shop originally. It’s been pouring rain here so was unable to recheck since they said it’s correct. I’m hoping to get to it this week.
 
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Double check it. It is amazing how many shops have no clue what it takes to get these things to drive down the road correctly. Buy an angle gauge or if you have an iPhone they have one built in that will work for this.
 
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I have angle finder. That’s how I knew it was 7* difference when I took it back. They assured me it was within specs now but after having new tires installed today it’s apparent that it’s not correct.
Hate to keep bothering the guy, but I’m thinking I should’ve just done all the work myself. I just didn’t want my Jeep being down for long time with the way my schedule is. Kinda look forward to jumping in it and going when I have a day off.
 
Put the angle finder on the ds. note the angle. Now put the angle finder on one of the flats of the rear diff.
78761

Subtract from 90* to get the pinion angle.
 
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What is the front DS and pinion angles? Possible when they changed tranny mounts it changed angles a bit. On mine 1-2 degrees out was all it took for vibrations. Try driving with out the front DS connected. When I was tracking down vibrations I disconnected front DS at axle and just zip tied it up to frame for a quick test drive. Quick and easy way to eliminate the front from the cause. Just make sure your not in 4wd.
 
Also check to make sure the DS is aligned correctly. An out of phase DS will cause some issues as well.79094