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Old 07-23-2012, 03:49 PM
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Default Death wobble

I've read about it for years, but never actually experienced it fully. I had been getting a weird steering vibration ever since the ride home from Moab this year, and had been gradually tracing it down.
I found a loose pitman arm, loose knuckle studs on one side, and one wheel bearing was slightly loose. My guess is that several years of pounding the truck on these Maze trips has taken its toll on the hardware.

I thought I had it all fixed, but the problem was still there. At highway speeds, I would hit a bump and it felt like a tire was out of balance for a second or two after. Not a huge deal, but weird. I took the truck by Robbie one day at lunch and in about 5 minutes he diagnosed shot TRE and trunion bearings. Funny part is that the TRE's were replaced 5 years ago or so.

On the ride home that day, I watched a Cherokee nearly wipe out on the interstate from this problem. Bump and then violent wheel shakes and he barely kept it under control to pull over. Friday on the way back from the Boulder, the same thing happened to me. Had to nearly clean my shorts after that experience!

All that said, I will be planning a full on knuckle rebuild along with a lot of other stuff that's overdue.

The tech part of this, is has anyone else with five five five TRE's had similar early failure of these parts? I think the main problem I'm feeling right now is more TRE than trunion, but it all has to go.
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Old 07-23-2012, 04:05 PM
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My TRE's have had to be replaced every 50k or so. I use the 555 brand.

I think we beat the **** out of that kid of stuff.

Oh, and if you figure out the DW, let me know. I still have a hint of it after replacing everything but my axle. Driveable, but you can feel it.
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Old 07-23-2012, 04:08 PM
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The 555's on my 40 are 3-4 years old and seem fine - no issues. But I don't drive my 40 nearly as much as you.
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Old 07-23-2012, 04:43 PM
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Quote:
Originally Posted by rover67 View Post
Driveable, but you can feel it.
And that is exactly why I posted this. I felt the same way. The wear in the TRE was only apparent when Robbie used a huge prybar on the joint to press it away from the knuckle arm. When he did that, you could just barely see it move. The Trunions have a slight "spot" in them that you can only feel when both tires are lifted off the ground and you turn the tires side to side by hand. I NEVER would have guessed that amount of wear would have produced the situation I had on the freeway. It was some scary stuff that I never want to experience again, especially in a SWB at speed. In fact, I may very well escalate doing the 450 to sooner rather than later because I suspect it also needs this maintenance.

The only other thing I can think of that may cause the DW might be slop in the steering box? Marco, I think both of us had our steering boxes rebuilt by the same guy...
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Old 07-23-2012, 07:40 PM
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good timing on this tread. I've developed an intermitant DW on the 80. I have not had a chance to really look into it but suspect TRE's as I replaced all the bearings last year during the knuckle service.

It was really bad over the Friday in Silverton and Ouray however only while braking. Not as bad in a corner. But Sunday driving to Pagosa and today around town nothing?
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Old 07-23-2012, 09:10 PM
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You know, I keep going back to the steering box, but I went through mine twice since the time I built it first. It sure seems tight, but maybe I am missing something?

I'll research the subject more...
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Old 07-23-2012, 09:28 PM
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Sure you don't just have hot brakes Corbet? My 80 would always shake about midway down Monarch Pass... but once on the flats again would be good for another year.
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Old 07-23-2012, 11:32 PM
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Granted, I've only read about death wobble, but I've read a lot. And talked a lot. That being said, take this with a grain of salt

You guys hit the common issues, but caster is often the root cause. A lifted truck without a cut and turn done often has it's caster out of spec, or just on the edge of spec. Combine that with worn parts, and death wobble ensues. Poor caster is very common on most leaf spring trucks. Especially if the axle has been turned at all for driveline correction.

Also, I know Marco has replaced everything, but look into the bushings on both ends of your springs.

On my buddies 87 4Runner with a SAS, he still had death wobble, even after brand new TRE's and new bushings in the leaf springs. Much of the issue can come from a lack of inner sleeve on the bushings. Some lift kits don't come with an inner steel sleeve in the bushings which is necessary for proper driving and keeping the spring immobile. Without the bushing, you just mash the bushings together, and they get destroyed quickly, and there is no support in the bushing for the spring to ride against.

And, be glad you guys have the 555 stuff. I used to burn IFS TRE's in a few months, and that was on 33's. 35's, and I lost a new one within 3 weeks.
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Old 07-25-2012, 09:30 AM
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Robbie was quick to mention the spring bushings as well, and I have never had mine out. The lift came on the truck when I bought it, and I hate it, so I had planned on swapping to something else. Coilovers would be my choice (ala TLC Icon style) but I have mixed feelings about continuing to modify my 40. Meh, it's parked now for a while, so I have time to pull it all down and find the issues.
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1978 13BT-40, 70 series mechanicals
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2003 100 stock
1974V8J40, 1992FJ80, 1985FJ60, 1971FJ55, 1978FJ40, 1974FJ40, 1997 LX450 all long gone.
KD0PZL
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Old 07-25-2012, 07:40 PM
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Quote:
Originally Posted by nakman View Post
Sure you don't just have hot brakes Corbet? My 80 would always shake about midway down Monarch Pass... but once on the flats again would be good for another year.
Could be but I don't think so. The rotors are only a year old and DBA slotted units. The worst wobble was right after exiting a trail that was mostly uphill. Then I climbed up the rest of the way to the top of Molas pass before descending into Silverton. So the brakes should have been cool going into my wobble.

I've tried to recreate the DW on my way to work this week. I drop about 1500' into Durango on my morning commute. Even riding the brakes I can't get it to wobble again.

I think the beating on the trail might be shifting a worn TRE? But I need to get the pry bar out this weekend and take a closer look.
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