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High Speed Vibration

976 Views 2 Replies 2 Participants Last post by  C4
Never had this symptom:

0-45mph - no issue
45-55 - ever so slight vibration and movement of the steering wheel only
55-65 - everything smooths out
65-80 - it feels like I'm driving on a cobble stone road and there is this low pitched rumbling throughout the vehicle. Scary! Especially doing 80 (which is the legal speed limit here in places before anyone asks)

What I know it isn't: Wheel Blanace, out of round tires

What mods I got: SA 4" TFP LCA's, 1" wheel spacers, stock rear DS (I have an 05 unlimited), TW Front DS, no lowering kit on the tranny, brand new Blistein 5100's on the corners. Other than that I can't think of anything else that would be relevent. I got to get this resolved because I need to go cross country in a few months.
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Two things from what I've dealt with on my rig-driveshaft balance-both front and rear to critical shaft speeds of around 4000 rpms. Not sure if you're running stock gears or a deeper set like 4.88's or 5.13's per se but with either, at 80mph you'll be spinning those shafts quick enough that a "standard" balance won't cut it and you'll get the symptoms you describe. Also if the joints are going bad in your shafts.

2nd thing that I'm going to take care of HOPEFULLY tomorrow when I do new brakes-your unibearings. They'll do similar/same type of thing. Are they still factory with 82K? Mine are making an intermittent squeel from time to time here and there, and at varying speeds like you mentioned, are emitting vibes. I'm all but 100% convinced that is the issue on mine-everything else is tight. They "feel" tight checking at the wheel, BUT don't spin SMOOTH like new-you can feel ever so slightly a rough spot in them. Mine stockers have about 73K-74K somewhere in there for reference and quite frankly, I'm surprised they're in as good a condition as they are.

Check those two things as they're a good possibility, somewhat easy to handle and basically somewhat cheap overall compared to other higher priced items that hopefully you won't need to mess with...

Another thing that is somewhat of a stretch but not really-I'm having a brain fart but what CA's are you running and what joints? Not decifering the code very easily tonight... :oops: If they're anything like stock rubber/clevite stuff, with that many miles, you can easily get enough movement in the axle to transmit vibes that show themselves in MANY different ways. If they are a factory type bushing, replace them with either new take-offs for cheap to get you through your trip, or something with a JJ at each end. This was the ONLY thing that totally eliminated the vibes from my front end and has kept it vibe free for the last several years. Mine are both ends, top bottom with the additional housing kit. Little more money though for this round of mods.

Best of Luck,

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Thanks for the reply. Stock upper CA's, Tera Flex Plus Lowers with their ends which are the same as JJ's. All check out good. Stock R & P for a Rubi. Wouldn't surprise me if that rear stock DS is out of balance for as much as I beat on it. I've been averaging 2,000 miles annually off-road. Unit bearings are still my originals so that could definitely be possible. I just replaced the wheel bearings in the rear, but it was doing this before that.
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