Re-geared, now I have a vibration above 50 mph

BendLarry said:
Be careful you may have messed up your caster.


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Yes, I'm aware of this. I was just focused on getting the pinion slightly higher. Drove fine on the way home, other than the same old vibes at 65. Have a wheeling get together this weekend, then next week, going to get it aligned and forget about it for the summer. Hard top is coming off this week, so it won't bother me as much with all the other extraneous noises related to top off driving. Problem is still not resolved, and that just grinds my gears!
 
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Man I always come here excited that at some point I am going to read "I finally got it!" but no, now I get, if I don't get it by this weekend, nothing till after summer. That is a cliffhanger like the tv shows I have been eye guzzling.

Will bobthetj03 finally get what he deserves?
Will bobthetj03 buy a new TJ by next sept?
Will bobthetj03 put the TJ out of its misery?
Will bobthetj03 admit that ac_ is right, and it was a tire/wheel issue the whole time?

Watch next season for another exciting season of bobthetj03 and his vibrating TJ to find out?

The suspense is killing me!
 
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ac_ said:
Man I always come here excited that at some point I am going to read "I finally got it!" but no, now I get, if I don't get it by this weekend, nothing till after summer. That is a cliffhanger like the tv shows I have been eye guzzling.

Will bobthetj03 finally get what he deserves?
Will bobthetj03 buy a new TJ by next sept?
Will bobthetj03 put the TJ out of its misery?
Will bobthetj03 admit that ac_ is right, and it was a tire/wheel issue the whole time?

Watch next season for another exciting season of bobthetj03 and his vibrating TJ to find out?

The suspense is killing me!
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I'll be feeding your need about the tire issue in the fall, since I'll be ready for new tires by then. If you are right, you will see my happy dance. Until then, I've done everything suggested. My jeep is being a fucktard!
 
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Shouldn't admit this, but lost my digital angle gauge in the process. Yep, left it on the front diff flat on one of my test drives. Retraced my route, but couldn't find it. It's the jeep gods telling me to just give up and drive it.
 
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bobthetj03 said:
Shouldn't admit this, but lost my digital angle gauge in the process. Yep, left it on the front diff flat on one of my test drives. Retraced my route, but couldn't find it. It's the jeep gods telling me to just give up and drive it.
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That sucks! But at least that isn't the most expensive tool in the tool box.
 
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A little update on my situation, I have added the currie MML and the Savvy 1.25" BL in preparation for the TT in hopes that the angle change will reduce the vibrations. After the MML and BL, my vibes were reduced by at least 50% if not more. Prior to it would they would start right at 55 MPH and now nothing till almost 65, and to the point that I can barely notice but it is still there. I am considering stopping at this point just because the TT is pretty major to go backwards on if the vibs come back or get worse. The only thing I don't like about the MML is that I get a little more vibration at idle sitting still but I'm pretty sure that is coming through the MML, but as soon as you get past idle is smooths out to nothing.
 
Regarding my earlier post in this thread (#371). I spoke too soon. I am experiencing a harmonic/vibration that starts as if someone flipped a switch at 67 mph. Adjusting the front pinion angle to match the front driveshaft angle helped a little, but the vibration is still there. Once the vibration starts increases in speed or rpm have no effect on character or intensity.

'06 LJ Rubicon, 4.0l, 42RLE, 241OR, 5" lift, Currie Correctlync steering, 35" tires, re-geared from 4.88 to 5.36. New Tom Woods front driveshaft. No vibrations or harmonics prior to re-gear to 5.36.

See this related thread started 7/19/18: https://wranglertjforum.com/threads...ations-after-re-gear-to-4-88-or-deeper.12218/
 
Raising my front pinion seemed to help a little. I was at -1.5* and rotated it up to +1.5*. From Blaine's advise, the front seems happier when the pinion is higher, and the rear pinion is happier when the pinion is lower. That is basically where I'm at now. Vibes still kick in at 63mph and pretty much is consistent up to 80mph. Don't go any faster than that. So far my steering hasn't gotten weird yet, but I'm afraid to go any higher up front. With the top off for the summer, it isn't too annoying because of all the other extraneous noises related to an open top jeep. Soon as I put the hard top on, the vibe will be amplified by the acoustics of the hard top.
 
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bobthetj03 said:
Raising my front pinion seemed to help a little. I was at -1.5* and rotated it up to +1.5*. From Blaine's advise, the front seems happier when the pinion is higher, and the rear pinion is happier when the pinion is lower. That is basically where I'm at now. Vibes still kick in at 63mph and pretty much is consistent up to 80mph. Don't go any faster than that. So far my steering hasn't gotten weird yet, but I'm afraid to go any higher up front. With the top off for the summer, it isn't too annoying because of all the other extraneous noises related to an open top jeep. Soon as I put the hard top on, the vibe will be amplified by the acoustics of the hard top.
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Am I misunderstanding this? When you say 1.5 do you mean above the stock 7?
Mine is right at 7 in the front. if change it the caster is all screwed up and it either wanders or the opposite and the steering doesn't return. I can run anywhere 6-8 or mine doesn't steer right. I don't have vibration issues, but also I am not geared like you guys either.

disclamer. this is with my 2 inch OME lift. as you know I ma in the middle of a currie so all of that above may be out of the window, but for now it I stand behind it.
 
bobthetj03 said:
Raising my front pinion seemed to help a little. I was at -1.5* and rotated it up to +1.5*. . .
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My front pinion angle was approx. 1 degree lower than the driveshaft angle. After the first adjustment the pinion angle and driveline angle are now each at 11 degrees. The vibration/harmonic has diminished somewhat but still begins at exactly 67 mph. [Speedo is calibrated with a SpeedoHealer.]

I have to drive 150 miles to a Cal4Wheel district meeting in Upper Lake on 7/21 and will take notes on what has changed since I adjusted the front pinion angle. Then back to my shop for more "fiddling."

What was your "sweet spot" for the front pinion angle [or more accurately the front pinion angle that has minimized your vibrations the most]?
 
Mr. Bills said:
My front pinion angle was approx. 1 degree lower than the driveshaft angle. After the first adjustment the pinion angle and driveline angle are now each at 11 degrees. The vibration/harmonic has diminished somewhat but still begins at exactly 67 mph. [Speedo is calibrated with a SpeedoHealer.]

I have to drive 150 miles to a Cal4Wheel district meeting in Upper Lake on 7/21 and will take notes on what has changed since I adjusted the front pinion angle. Then back to my shop for more "fiddling."

What was your "sweet spot" for the front pinion angle [or more accurately the front pinion angle that has minimized your vibrations the most]?
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I'll be working on the jeep tomorrow at my shop in Lakeport. I'd be interested to see what your vibes are like compared to mine.

As it sits right now, the rear pinion angle is 1.5* lower than the driveshaft angle. The front pinion angle is 1.5* higher than the driveshaft angle. I'm measuring using a digital angle finder, placing it on one of the diff flats for the pinion angle measurement,
20170707_082809.jpg

And on the driveshaft tube to get the driveshaft angle,
20170707_082731.jpg

I was double checking the digital angle finder with my dial angle finder for accuracy.
 
Trying to visualize the tummy tuck scenario. My crude drawing helps me picture what's going to happen, sort of. by raising the TC skid, using the motor mounts as the fulcrum point, you are actually decreasing the operating angle of the cardan joint at the TC input. Inversely, you are also increasing the rear drive shaft angle.
20180720_140951.jpg

If indeed the vibe problem is happening as a result of the TC input yoke angle and increased driveshaft rpm's, then it's a crap shoot if you end up just trading the problem to the rear driveshaft if the operating angles become too steep. It is surely a slippery slope screwing with Jeep's drivetrain geometry.
 
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Raising the front diff pinion angle will also lower the angle of the front drive shaft, thus lowering the operating angle at the TC input.
 
bobthetj03 said:
Raising the front diff pinion angle will also lower the angle of the front drive shaft, thus lowering the operating angle at the TC input.
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That line of thinking illustrates why I asked about your "sweet spot" (or least worst spot) for the front pinion angle, i.e. the front pinion angle that has minimized your vibrations the most, in terms of degrees +/- equal pinion and driveshaft angles. I think I read that you tried +1 degree with no change but am not clear exactly what angles you tried on the + side.

In the case of my particular vibration it appears that if a simple front pinion angle adjustment is insufficient the only sure fix will be to convert to manual hubs. I think I'm good for one or two more adjustment sessions before I bite the bullet and move forward with new hubs. Your observations when you raised your front pinion angle above the driveshaft angle may help make those one or two adjustment sessions more productive.
 
Mr. Bills said:
That line of thinking illustrates why I asked about your "sweet spot" (or least worst spot) for the front pinion angle, i.e. the front pinion angle that has minimized your vibrations the most, in terms of degrees +/- equal pinion and driveshaft angles. I think I read that you tried +1 degree with no change but am not clear exactly what angles you tried on the + side.

In the case of my particular vibration it appears that if a simple front pinion angle adjustment is insufficient the only sure fix will be to convert to manual hubs. I think I'm good for one or two more adjustment sessions before I bite the bullet and move forward with new hubs. Your observations when you raised your front pinion angle above the driveshaft angle may help make those one or two adjustment sessions more productive.
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Agreed @ making one or two more adjustments. Probably will happen when I change out my Duroflex joints. I figure I might as well go till my caster turns to shit, then back off from there and see what I net. Changing to manual hubs up front will be a very tough sell to the Mrs. That is, if it is even possible with my BBK.
 
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