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Unread 06-09-2015, 03:56 PM   #1
cuzsis
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Tires/Jeep bounces badly after hitting bumps

The other week, I was doing 70mph on our freeway (the speed limit) and moved into the center lane. The center lane has large grooves from the semi trucks and as my tire bounced as it went into the groove. It kept bouncing and, once I was in the center lane, the entire jeep was bouncing and shuddering. At first I thought the road was really bumpy...nope.

I slowed down and pulled off to get towed. It stopped once I got back under 50 or so.

Shop said the front end was fine, but my rear diff was out of fluid (I just had it changed last year at a local jiffy lube, and the slow leak had gone 4 yrs before changing, so I'm skeptical as to how that happened....)

They put fluid in and said it would be fine.

It wasn't. Not a week went by and it did it again on a bump, I slowed til it stopped and sped back up. And then again this Saturday when I hit a bump crossing a bridge at about 55mph, stopped when I got to 45 or so. No puddles of diff fluid that I can tell when I park either.

The shop swears I did damage to the diff and that it needs a costly replacement. Problem is, my mechanic has moved shops so these guys are new and I don't trust them yet.

I've had no signs of dragging or grinding. I can get a thump when I shift into drive, but since Jiffy lube changed my trans fluid, I'm inclined to check that now too. :P

I'm planning to check my tire balance at my Les Schwab, and get a second opinion if I can swing it, but work is pretty busy right now. Sadly we just moved and the new garage is only half finished, so I'm in a bind for sussing this out.

My question is, has anyone heard of a wearing/busted diff causing this?

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Unread 06-09-2015, 04:50 PM   #2
green98ZJ
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Sounds like your front end needs some help and your jeep has death wobble. I don't think your mechanics are being truthful
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Unread 06-09-2015, 04:55 PM   #3
MrRoundel
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That sounds a bit like the infamous Death Wobble (DW) to me. Do a search on "Death Wobble", and compare your symptoms. I believe that hitting a bump usually sets it off. That said, your shop should know about DW.

I too would think you'd have some grinding or whining sounds if it was from your differential being dry. Where was the slow leak coming from? Differential cover? Bad axle seal?

(I just saw someone beat me to the draw on the DW. Like I said, use the search function, and search "death-wobble". Good luck.)
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Unread 06-09-2015, 05:06 PM   #4
kg6mov
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You have death wobble. You need to go over your front end and will probably find a couple things that are contributing to it.

Most common culprits are the track bar and the control arm bushings. If the control arms are or could be original they should be replaced right off the bat. The track bar mount on the axle side can wallow out allowing movement of the axle which causes the shaking you described.

The CA bushings are hard to test, they can look fine and be giving you wobble. The track bar is easier, with the engine running have a friend turn the wheel back and worth and look for any movement in the track bar mounts axle and frame side.
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Unread 06-09-2015, 07:39 PM   #5
merlot2twisty
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I had death wobble that was caused by a tire out of balance. I replaced teh track bar and control arm bushings before I had to buy new tires. Anything that can set up a vibration in the front end can trigger it.

Scares the bejeesus outta ya, doesn't it?
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Unread 06-11-2015, 07:11 PM   #6
cuzsis
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Thanks everyone. I agree, it's almost certainly death wobble.

Les Schwab said that since I bought rear tires only last month they're probably not out of balance. We replaced the track bar a few years ago, but I've heard that the life span of the part is less than I had hoped for. So perhaps that's it again? (Had death wobble back before the track bar replacement, but it was pretty consistent.)

My steering is loose and it appears to be the box. Our new road to the house is a mountain logging road with various potholes. My steering was noticeably worse today, which is almost certainly due to the road.

Could the steering box could cause death wobble? I've heard one person mention it can, and other people say it can't.
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Unread 06-11-2015, 07:20 PM   #7
kg6mov
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It can't cause death wobble in the traditional sense (axle moving side to side), but it can certainly cause similar symptoms.
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Originally Posted by Texas ZJ1 View Post
I heard someone yell "mall crawler" from the back porch. I'll go see who said that. Be right back.
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Unread 06-11-2015, 10:10 PM   #8
Worlocke
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Go have your front tires balanced, if it started all of a sudden, and the front end looks good I would be willing to bet a weight fell off
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Unread 06-13-2015, 10:18 PM   #9
cuzsis
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Quote:
Originally Posted by kg6mov View Post
It can't cause death wobble in the traditional sense (axle moving side to side), but it can certainly cause similar symptoms.
In what ways would it differ from death wobble? Is it something I could potentially tell while driving?
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Unread 06-13-2015, 10:20 PM   #10
cuzsis
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Quote:
Originally Posted by Worlocke View Post
Go have your front tires balanced, if it started all of a sudden, and the front end looks good I would be willing to bet a weight fell off
The weights still appear to be clipped on, but I will admit I haven't kept careful tabs on them.
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Unread 06-14-2015, 07:42 PM   #11
robrtsmtn
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I wouldn't say anything negative about Les Shwab as I have lived in the NW a while. However, let's just say generically I have had places rotate and balance for me where a vibration was worse when I left than when I pulled in. Within the last two weeks, I had a tire go flat (not uncommon here in the high desert where anything will sting, stick or bite you), put fix a flat in, aired tire up and as my son and I were heading out for a jeep weekend in the SW Colorado San Juans. I got the death wobble bad, seriously scary, before I got out of NM. This weekend, my son and I swapped front tires for rear as a last check before bushings, and the front end was smooth as glass. Just saying before you tear into the front end, having someone else balance your tires is a cheap KISS rule type of check before you spend bigger bucks.
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