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Northern Virginia Jeepers Association
July 20, 2018, 07:33:10 AM

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Author Topic: Vibrations.... Still....  (Read 232 times)
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sirjames186
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05 LJ
« on: July 11, 2018, 01:34:38 PM »

Need some help, I've been fighting drivline vibrations at and over 60mph since I regeared to 4.88 and installed a HPD30. I'm moving on Monday and took it to a ORI to get it all fixed before the move. They replaced the trans fluid and filter (auto trans), gave it a full alignment, and rebuilt my front gears because they were all jacked up (plus some other odds and ends). Figured that would solve my issues. Wish I could say it did. It still has a pretty bad harmonic driveline vibration over 60. It's definitely not tires or anything like that. The shop has now rebuilt and balanced both front and rear driveshafts, triple checked angles and alignment to no avail. They say without the front shaft in, it'll go to 70 before the vibrations start, but it's kicking their butt to get them to go away completely. It has to be something in the transfer case or transmission at this point and I need to pick it up on Friday. Anyone have any ideas or had something similar? I'm at my witts end with everything else going on and this on top of it.

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overhead
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Crap, someone call Trevor.
« Reply #1 on: July 11, 2018, 01:49:19 PM »

stupid things first.

did you check t case mounts, engine mounts, and the like with all that? what about sticking a gopro or what not underneath to see if something is happening that's identifiable

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The only thing about a Yj that's reliable is its mechanic.

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atjeep-Every time a YJ passes inspection, an angel gets it's wings.
highlandercj-7
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« Reply #2 on: July 11, 2018, 02:40:39 PM »

Where do you feel the vibs? Floor, seat, steering wheel, or is it just audible?

Do this too: put it in 2nd gear and turn the RPMs that you would at 70 and see if it comes in at the RPM as well and not just at the speed. IE if you did 2800 at 70 in drive do 2800-2900 holding 2nd and see if it's there.

Also does it do it if you rotate the tires? I know you said it's not them but I have has several sets do that at 65 ish MPH. 60 and below they were fine 70 and above they were fine.

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HighlanderCJ-7
sirjames186
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05 LJ
« Reply #3 on: July 11, 2018, 02:49:40 PM »

Feel them in the seat. It shakes the change in my cup holder. They roated the tires while at the shop and it's still there. It rotates pitch in a low growl type noise every 2 seconds or so. High/low vrrrrrVRRRRvrrrrrVRRRR Tough to explain over text.

It's still at ORI so I'm not sure if it's RPM related. I know I've driven it and they have as well, everything is fine until 60 mph. I normally turn about 2400 rpms at 70 so I'd definitely be hitting that range around town in lower gears under 60 with no vibration.

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sticksout
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« Reply #4 on: July 12, 2018, 06:50:25 AM »

Did you replace your speedo gear to account for your new tire/gear ratio?

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2001 TJ Sahara - black
sirjames186
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« Reply #5 on: July 12, 2018, 09:06:06 AM »

Did you replace your speedo gear to account for your new tire/gear ratio?
Yes, 49 tooth I think it was.

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TakHardRock
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« Reply #6 on: July 12, 2018, 10:02:06 AM »

I had vibration after upgraded to 4.88, but my was at about 50 to 60 then go away when I pass 60. My vibration is from the floor. I met a guy at some jeep meet and he had the same issue.

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sirjames186
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05 LJ
« Reply #7 on: July 12, 2018, 10:45:05 AM »

I had vibration after upgraded to 4.88, but my was at about 50 to 60 then go away when I pass 60. My vibration is from the floor. I met a guy at some jeep meet and he had the same issue.

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Thinking about it I would say it's more the floor than seat. I don't feel it, but I hear it.

I've been asking a lot of the LJ guys and it seems this is a common thing for the 42rle transmission and 4.88. They all solve it by disconnecting the front shaft unless wheeling. I'd be fine with that except the vibes are still there with the front shaft out.

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sirjames186
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« Reply #8 on: July 12, 2018, 03:15:27 PM »

I think I've figured this out. On paper at least.

As mentioned all the LJ guys have the same issue with 4.88 gears and auto trans. Almost all (few I don't know the specs on their lift for) have a motor mount lift. My thinking, and something I noticed when I tried to align the front pinion as well, is the mml tilts the engine and transfer case up ever so slightly. Normally this isn't as issue. However with the 4.88 gears things are spinning faster than normal. The slight upward tilt of the transfer case with the faster driveshaft speed is enough to cause the vibrations in the front. The cv joint is supposed to solve this, but for some reason at highway speeds it just can't hold its own. To solve it, add a tummy tuck and raise the transfer case like you did with the mml. I figured this out because everyone with a tummy tuck doesn't have the issues but those with the stock skid do.

Sounds weird I know, but it's what the evidence suggests. Am I going insane? Maybe. But that's my theory and I'm sticking to it!

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overhead
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Crap, someone call Trevor.
« Reply #9 on: July 12, 2018, 03:20:27 PM »

I think I've figured this out. On paper at least.

As mentioned all the LJ guys have the same issue with 4.88 gears and auto trans. Almost all (few I don't know the specs on their lift for) have a motor mount lift. My thinking, and something I noticed when I tried to align the front pinion as well, is the mml tilts the engine and transfer case up ever so slightly. Normally this isn't as issue. However with the 4.88 gears things are spinning faster than normal. The slight upward tilt of the transfer case with the faster driveshaft speed is enough to cause the vibrations in the front. The cv joint is supposed to solve this, but for some reason at highway speeds it just can't hold its own. To solve it, add a tummy tuck and raise the transfer case like you did with the mml. I figured this out because everyone with a tummy tuck doesn't have the issues but those with the stock skid do.

Sounds weird I know, but it's what the evidence suggests. Am I going insane? Maybe. But that's my theory and I'm sticking to it!


So... If I'm reading this correctly. You're gonna convince the wife to tummy tuck the lj the week before a move to solve a vibration issue potentially?  Big Eyes


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The only thing about a Yj that's reliable is its mechanic.

Joey to Mike- That's more like it! Never done.....just outta money at the moment.

atjeep-Every time a YJ passes inspection, an angel gets it's wings.
sirjames186
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Posts: 2392
05 LJ
« Reply #10 on: July 12, 2018, 03:23:10 PM »

I think I've figured this out. On paper at least.

As mentioned all the LJ guys have the same issue with 4.88 gears and auto trans. Almost all (few I don't know the specs on their lift for) have a motor mount lift. My thinking, and something I noticed when I tried to align the front pinion as well, is the mml tilts the engine and transfer case up ever so slightly. Normally this isn't as issue. However with the 4.88 gears things are spinning faster than normal. The slight upward tilt of the transfer case with the faster driveshaft speed is enough to cause the vibrations in the front. The cv joint is supposed to solve this, but for some reason at highway speeds it just can't hold its own. To solve it, add a tummy tuck and raise the transfer case like you did with the mml. I figured this out because everyone with a tummy tuck doesn't have the issues but those with the stock skid do.

Sounds weird I know, but it's what the evidence suggests. Am I going insane? Maybe. But that's my theory and I'm sticking to it!


So... If I'm reading this correctly. You're gonna convince the wife to tummy tuck the lj the week before a move to solve a vibration issue potentially?  Big Eyes
Lol, I'll pull the front driveshaft and convince her of the tummy tuck later.

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zuke
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« Reply #11 on: July 12, 2018, 05:46:21 PM »

Have you considered removing the MML? With a 3 inch lift on an LJ, I don't believe it's really neccessary though it's right at the limit...

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John
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sirjames186
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Posts: 2392
05 LJ
« Reply #12 on: July 12, 2018, 06:49:25 PM »

Have you considered removing the MML? With a 3 inch lift on an LJ, I don't believe it's really neccessary though it's right at the limit...
At this point it would be more work to remove it. It's been in there for almost 2 years and wasn't an easy install. Broke a bolt and everything. Disconnecting the front driveshaft until a tummy tuck is no problem. If this tune up hadn't gone over budget I had that on the list for this fall anyway.

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"I'm no longer ashamed to wheel with you." - Jeremy
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