How can I figure out why I have death wobble? (2 Viewers)

[bjp]

I have a 1993 with death wobble that I've tried to fix and it's still not fully gone. I'm sure there are many things I could blindly try if I had infinite money, but how can I figure out which one is actually likely to fix the issue?

I know this is a bit long, so to encourage responses: I'd be excited to send $50 to whomever first describes a diagnostic procedure which leads to diagnosing an issue that, when fixed, solves the problem. Just throwing out things it could be doesn't count unless accompanied by some test I can perform to confirm or deny whether that thing is actually the main problem before spending money and time addressing it.

When it started
I'm completely new to Land Cruisers and vehicle maintenance in general. I bought this LC in March with 163k miles and I've been baselining it ever since, so I've put less than 1k miles on it. I thought I had the minimum set of stuff done in September so I took it to an offroad picnic about an hour away by paved roads. Just before hitting dirt, I got my first death wobble around 30 mph. I thought "that was crazy", but the pavement was a little rough and I hadn't heard about death wobble before, so I did a bit of light offroading then started home. A fire forced me to take (paved) back roads for 23 miles and I got probably 8 or 9 wobbles. By the end, I was trying to intentionally trigger them to figure out what the trigger was, and I was trying various things to mitigate them instead of just braking hard, but I couldn't find any reliable patterns.

Behavior
The wobbles always started between ~20 and ~55 mph -- I took it carefully on the freeway on the way home after the wobbles on the back roads and got zero wobbles on 28 miles of freeway, then one more wobble on the 1.5 miles between the freeway and my house. The wobbles seem to be more likely to happen while on a slight curve (especially when the curve direction changes), when hitting small bumps (but larger bumps don't seem to do it), and when slightly braking, but even a combination of all these factors doesn't guarantee a wobble, and not all factors are necessary to produce a wobble. Again, I could never figure out when they would or wouldn't happen.

Initial investigation
When I got home, I found the jam nut of my front adjustable panhard rod completely disengaged, so I tightened that jam nut. I could grab the drag link or tie rod and rotate them on their axis by hand fairly easily, but I didn't feel any play. I jacked up each front wheel one at a time and tried to wiggle the wheel while grabbing at 12 and 6 and I didn't feel any play. I tried to wiggle while grabbing at 3 and 9 and did turn the wheels a bit, but didn't notice any play. I took off the mud guard of the driver front wheel and looked at the frame and panhard tower around the steering box and didn't see any cracks. I measured 30.15 PSI in front passenger tire and 30.65 PSI in front driver tire, and both wheels still had balancing weights attached (though I can't rule out some falling off). The two of four knuckle nuts I could easily access with my torque wrench were still torqued to at least 71 ft-lbs and the other two were "tight" (both sides).

After tightening the panhard jam nut, I took it back out on a 45mph street and got 2 more wobbles within 3 miles. A member of my offroad club diagnosed needing new rod ends.

Attempted fixes
I bought the Trail Gear Heavy Duty Steering Kit which includes a new drag link, tie rod, 4 rod ends, and a steering damper. I took off both rods, damper, and the steering box and had the steering box professionally rebuilt. The old steering damper was pretty much entirely done -- spring only, virtually no oil resistance. When reinstalling the steering box, I replaced the high pressure hose with Gates and the low pressure hoses with Gates from phhkit.com. I installed the new tie rod and used two aluminum angles to set 1/8" toe in at 37" wheel diameter, using two laser pointers to center the steering:

I installed the new drag link and tried to center the steering wheel as closely as possible using the two laser pointers on my alignment jig shown above. All crown nuts torqued to 67 ft-lbs plus whatever was needed to line up the cotter pin holes. The Trail Gear rods use jam nuts and do not have any indents to put a wrench on (!), so I tightened the tie rod jam nuts to TG's recommendation of 75-85 ft-lbs using a giant 14" set of vice grips and a giant adjustable wrench. I tightened the drag link jam nuts with just the wrench to "medium tight" because I knew I would need to adjust the steering wheel position a bit more. I did NOT install the new steering damper because one of the bolts was missing and Trail Gear has STILL today not delivered that missing bolt (they blame PROcomp, the steering damper manufacturer), but my understanding (which could definitely be wrong!) was that the steering damper just masks the issue and is never the root cause, so it seemed ok to leave it out initially. I also got my front wheels professionally balanced. Unrelated(?) to these fixes, I also installed a new Tom Woods DC front driveshaft.

Results
After these fixes, I drove a 38 mile loop including 23 miles of paved mountain roads like the ones that triggered so many wobbles. Zero wobbles. I did feel some "incipient shimmies" (vibrations like the ones that preceded death wobbles) which worried me a little, but I don't know the truck super well so I figured those may just be normal solid axle stuff. Given that I got 2 wobbles in 3 miles before the fixes, I thought for sure I would see wobbles in the big circuit if they were still a problem. The drag link did come loose from its jam nuts during the circuit because I hadn't done the final tightening yet, but even with the drag link working its way loose, still no wobbles. So, I considered the issue probably fixed and moved onto the next work.

Going to the picnic, I also had the AC shut off from overtemp while climbing a steep freeway grade on a hot day, so I did a bunch of cooling work next including replacing all of the heater hoses, replacing thermostat, replacing fan clutch with new 95F/6500cst-modded clutch, replacing radiator, and adding a temperature sensor to the upper radiator hose.

I went to do a short test drive to also re-set the drag link properly and...got a death wobble a short distance before my house. Well crap. I finished dialing in the drag link length and tightened the jam nuts to basically the gripping limit of the vice grips, then drove the same 38 mile loop. No death wobbles, but still a bunch of "incipient shimmies".

So, I don't really know what to do. I don't think tightening the drag link jam nuts should have made the difference between wobble and no wobble since I wasn't getting wobble on the big circuit even when the drag link was loose. But, it's also now apparently hard to actually reproduce the wobble. I feel like I can't take the LC on trips because I'll probably see wobble at some point since it was still present after all the fixes (not taking it on the trip I'm leaving for today because of this).

Configuration
When I bought the LC, it already had:

• 37" Cooper Discoverer STT Pro tires with most of their tread life remaining
• Method 105 beadlock wheels
• OME 419 Comp Coils in front, unknown OME coils in back, resulting in ~5" lift based on DeltaVS's panhard bolt method when lightly loaded (but still have front & rear bumpers + winch on front + full-size spare on back)
• Front sway bar removed
• 5.29 diff gears (net result from 37" tires + 5.29 gears = truck travels 92% as far as speedometer/odometer thinks it went, so slightly lower gearing than stock)
• Air locker front, Detroit locker rear

Not very many miles before the picnic, I installed new DeltaVS radius arms for a 4" lift. I tried to get before & after caster numbers, but no shop around here will measure alignment on beadlock wheels, and I gave up trying to measure the caster accurately.

I had recently removed all wheels (one at a time), deflated, carefully and progressively torqued all 120 beadlock bolts, reinflated, and reinstalled.

Both the previous owner and the one before that are members of my offroad group (I joined shortly after getting this truck). The previous owner had a bunch of stuff put on the truck (including air locker), but drove it only a few hundred miles over 2 years. The second-previous owner (an experienced amateur mechanic) said the front axle "is basically all new" -- he said he thought he did the rebuild at 13Xk, but based on CarFax, I don't think he owned it until 145k (he works on a lot of cars, so not surprising his memory may not be perfect).

Possible things to try
I can think of a number of things that hypothetically might address the issue:

1. New non-beadlock wheels + new smaller (35"?) tires
2. Knuckle rebuild, including new wheel bearings
3. Install steering damper
4. Add a front sway bar
5. Replace some of the front axle components (not sure which ones)

I'd be happy to do any of these to fix the issue, but doing all of them would be very expensive, especially when it seems like there's no guarantee that even doing all of these things would fix it. #2 seems like the leading candidate to address any wheel bearing problems, but it seems like the fact that there's no play in the wheels wiggling at 12 and 6 would suggest that the wheel bearings aren't the issue (plus, the wheel bearings were probably replaced 20k ago). #3 will probably "help", but if it were just hiding the underlying issue, that seems like it would actually make things worse by making the underlying problem harder to find. Could #4 actually affect death wobble? I'm not sure what I would be targeting in #5; are there any components that might be causing the wobble? #1 seems like the most likely solution (but I don't really know what I'm talking about yet), but $3k-$4k is awfully steep for "most likely". I want to get non-beadlock wheels eventually in any case, but I really like the Coopers and would like to keep 37s if I can figure out this death wobble issue.

Thanks for reading; thoughts?

 

[COYS]

Good point on MOUNTING the rim off-center, I'll pay attention to that moving forward! Definitely foreseeable with these massively heavy wheel/tire combos.

I mean, they're mounting it hub-centric to balance (on a non hub-centric rim!) and then I'm mounting it lug-centric on my vehicle......as an engineer with some GD&T experience under my belt, it makes perfect sense that this could lead to repeatably inconsistent results.

This is why I dumped my beloved 16x10 D window steelies for hub-centric aftermarket wheels with acorn lug nuts. Due to the immense popularity of Toyota Tacomas, 4Runners, Tundras, there's no excuse to run anything but hub-centric aftermarket wheels (hub rings don't count) on your 80 series.

Steelies are much heavier than alloys. They're also manufactured to a much lesser quality even compared to the ubiquitous made in China Wheel Pros brand alloys on 99% of the modified trucks you see on the road today. It's not uncommon that a steel wheel has poor run-out values sans rubber.

• I only enlist tire shops that use Hunter Roadforce machines
• Whenever I rotate my 37s, I spend the money to have them roadforce balance each wheel simply because I detest any odd vibrations on all of my vehicles
• I use these centering style acorn lug nuts for extra peace of mind

 

[toyotaboy80]

Im probably looking at this semantically at this point I guess.

Nothing really prevents death wobble like caster. Caster on the right knuckle resists a right turn and caster on the left knuckle resists a left turn. As the knuckles turn, the reason they return to center because the one side is higher than the other and the raised side forces it back to the other side. When a wheel gets hit from 1 side, the opposite side is stablizing that from whipping.

As far as I know there is no other component or angle that counter acts the death wobble movement.

@bjp That video shows exactly what death wobble is. And that is bump induced death wobble. I would imagine many other driving instances would cause THAT jeeps steering to behave that way. I wonder if he had a caster only issue and if his other 2 loose components had anything to do with the substantial fix.

Also, you didnt quote the rest of what I said. I was questioning IF the term death wobble is being used appropriately. Example: just because one has a tire imbalance, doesnt mean they have death wobble. Just because one has a wobble after smacking a bump, doesnt mean they have death wobble. There is a reaction for the actiom of hitting a bump. Even im a perfect world driving a solid axle truck on 37's is going to produce a bobble wobble bounce shimmy whatever you want to call it when you slam a bump at 25mph. It might not be death wobble. Hence, if the term is used inappropiately, one might claim a perfectly normal albiet undesireable characteristic as death wobble.

 

[alia176]

I wonder if he had a caster only issue and if his other 2 loose components had anything to do with the substantial fix.

Here's the end of the video;

 

[jellis]

As far as I know there is no other component or angle that counter acts the death wobble movement.

The steering damper!!!! Take the absurd example of a nearly incompressible damper, there will definitely be no DW if all other components are tight.

With caster everyone gives the example of shopping cart wheels, but once you have someone standing on the front of the cart they tend to track correctly. The countering force of caster angle could be calculated during DW, but regardless it's going to be a pimple on a dimple on a horses butt compared to whatever is going on with BJP's data showing ~300+ lbs wobbling at 12.8 Hz. That's INSANE!!! Caster forces at that time would be like a light breeze on a spinning top. I mean, even the noteworthy force you exert thru the steering wheel is irrelevant, let alone caster forces. The problem with both steering and caster forces is that they don't vary with frequency, and in order to dampen harmonics you need frequency-dependent counter-acting forces. Hence, a steering damper....and a harmonic balancer....and shocks, etc. for all these systems that encounter harmonics. Like Mudgudgeon said earlier, there is not necessarily one single cause for the harmonics, but there really is only one component in the system designed to dampen harmonics (preferably before they really start).

@COYS Thanks for your comments on rims, what exactly did you go with? I looked into this quite a bit but the offset/stuffing issue with 37s made it less straightforward than I anticipated!

 

[COYS]

@COYS Thanks for your comments on rims, what exactly did you go with? I looked into this quite a bit but the offset/stuffing issue with 37s made it less straightforward than I anticipated!

I went with these and also the KMC Terras that recently debuted which feature the same specs as the ubiquitous SCS F5s.

For Sale - Los Angeles: 17x9 Summit Off-Road Sierra wheels (qty 4 in black) - https://forum.ih8mud.com/threads/los-angeles-17x9-summit-off-road-sierra-wheels-qty-4-in-black.1277945/post-14351913

Both sets weigh mid 20lbs, truly round (I verify every time I buy new wheels), and hub-centric with the Sierras sitting ~.5” more inboard than the Terras.

 

[Pin_Head]

DW is due to two factors:

1. Excessive play or slop in anything that locates the wheel. Excess play is necessary for the harmonic wheel oscillation. No play, no DW. The problem in diagnosing DW is that there are so many different things that can locate the wheel and many of them are easy to overlook.
2. An initiating force, like hitting a bump or going over railroad tracks. Caster angle players a part here because the initiating force needs to be high enough to over come the self-centering force of caster.

In diagnosing excessive play, you can find the source of the slop by putting the truck up on a lift and then using a 6 fooot pry bar to find things that move that shoudn’t, or put a GoPro camera on the undercarriage and film the DW to see what is moving. The old school way is to stick your head out of the window and look at what is happening. Sometimes what you see is surprising, like only one side oscillates or the entire solid axle assembly is moving back and forth L to R while the steering linkage doesn’t move. Sometimes you find that you whole steering box is moving because the frame is cracked. Seeing is believing.

I have never seen a situation where replacing a steering dampener fixed the problem.

The other way to diagnose it is to guess what is wrong by randomly replacing parts suggested by others that have had the same problem. The first way is faster and cheaper.

 

[jellis]

In my experience it would appear that tires alone can cause DW, and they can do so without hitting any initiating bump. I did the 6' pry bar thing on my lift a ton of times over a period of years, mostly it was totally uninteresting. I usually found something visually (e.g., cracks in frame) during this process which I corrected. Despite not finding anything with the pry bar, I replaced a bunch of crap (such a radius arms to correct caster, a lot of things damaged from DW....I literally replaced everything front & back except for steering box, even the front spindles). Replacing all the crap didn't fix it. This would indicate that my 6' pry bar analysis was correct in that there was nothing adequately loose, but it DID NOT resolve my DW.

It makes sense that a 6' pry bar is not a fool-proof analytical tool because it's a static analysis of a dynamic problem. It's like saying you can analyze a structure's ability to withstand an earthquake by slowly pushing on one wall and seeing what happens. That will tell you if a wall isn't connected to the trusses, but it can't tell you if you need twice as many nails at each connection. The huge variable is the magnitude of the earthquake, and in our situation that's set by the giant rotating masses on each wheel which sets the magnitude by:
1) Being out of balance, perhaps opposite between sides to make it worse....bent rims are also in this category
2) Reacting in a certain harmonic way to bumps ("roundness" of profile), especially across sides. Maybe static vs. dynamic tire balancing is related to this category? I haven't looked into that yet.
3) Having loose components which essentially just allows small harmonics to explode into large harmonics....this is similar to the next category.
4) Having no harmonic damping, e.g., steering damper. Once lifted the angle on the damper gets AWFUL and you probably need twice the damping of an unlifted rig just to breakeven with factory-intended damping on the steering mechanism.

In hindsight, I believe most of what I found wrong with my rig was a consequence/result of DW and not a causal factor. Bent radius arms, bent steering linkage, cracked frame, etc. This would also explain why fixing those things didn't resolve the issue.

 

[leonard_nemoy]

As far as I know there is no other component or angle that counter acts the death wobble movement.

80 series cruisers can and do develop cracks in the frame around the panhard mount and steering box. These cracks will not effect caster.

There are many instances of 80 series that are properly lifted and set up with proper caster that develop these cracks and death wobble follows. Than the owner uses fish plates and repairs the cracks curing the death wobble.

There are also instances of stock 80 series that have no suspension mods or worn out parts that develop these cracks and also experience death wobble. Again, nothing wrong with caster in these examples.

Many other things can cause death wobble in a vehicle besides caster. Excessive play in the steering linkage caused by cracks in the frame on an 80 series is a prime example.

 

[Pin_Head]

In my experience ….…. fixing those things didn't resolve the issue.

Just because you didn’t find the source of the excess play, doesn’t mean it isn’t there. Maybe you din’t pry the right places or hard enough. Fixing things that don’t create the play don’t help as you have discovered. Put a camera on it and see what is going on. Seeing is believing.

 

[leonard_nemoy]

@alia176

Did you make any progress on the DW?

 

[alia176]

@alia176

Did you make any progress on the DW?

I don't drive the 80 frequently but did go into town for breakfast. I had no DW last sat and no wheels are out of balance. I found this to be interesting as I took the same route to get to the freeway, hit the same bumps, expansion joints, etc.

I checked the torque on ALL the suspension hardware (F+R). I did find one loose hardware that I didn't torque after front radius arm bushing swap (last Oct). I haven't gone for a drive since then. The knuckles are still had the correct torque values.

Tie rod ends were tight. I have a 3" lift with Slee caster plates running OEM bushings everywhere.

I still need to check front wheel bearings play after I bring it down from the rack.

If I still have DW, I'll swap the tires front to back to see if that makes a difference.

 

[OffRoadScott]

While driving back from grabbing food last night I hit a bump in the road after going over a bridge and got what I thought was/is death wobble. I crawled under the LC and checked the suspension components, I could not see anything wrong. Also, lifted the front end and checked for play in the wheels and nothing other then grabbing at 3/9 and getting play from the steering link. Could that be my issue?

Read in this post that tire balance could be a issue. It has been sometime since mine have been checked and it did sit for awhile prior to being my DD again. Do have an appointment Friday for a rotation and balance.

This morning I drove the exact same road nothing.

 

[alia176]

@alia176

Did you make any progress on the DW?

It's been a while since my last update and I got back from a road trip to UT last sunday. I do have a front tire slightly out of balance around 45-50mph but other than that, no more DWs for me.

 

[alia176]

Yup, I have DW and I'm leaving for a trip in two days. Wheel and trunion bearings are my only suspects.

It comes on at approximately 48 mph to approximately 52 mph and ALWAYS going straight. My GF drove the 80 without me in it and she pulls up to my house and asked me WTF is up with your 80

New panhard rid bushings, torqued hardware.
Tie rod ends are tight
Radius arm bushings are also new and hardware torqued.

That leaves two sets of bearings to check, should be easy.

 

[Zjohnsonua]

I do have a front tire slightly out of balance around 45-50mph

If you're heading out for a trip imminently, here are a couple others to check and/or complete:

-get your tires balanced on a road force / dynamic balancer. If you've got a tire failing it'll show as imbalance and can cause DW. This balancing method will show that failure if it exists.
-you mentioned tie rods, but not drag link. check your drag link ends, too.

 

[COYS]

-get your tires balanced on a road force / dynamic balancer. If you've got a tire failing it'll show as imbalance and can cause DW. This balancing method will show that failure if it exists.

+1

I’ll even recommend that hunter road force balancing should be standard procedure for every mount and balance job. You can look up locations of shops that have their latest machines on their website. Ensure you explicitly tell the rep you want force matching but your priority #1 is to give your business to a reputable shop who have trained techs and maintain their hunter machines to deliver the intended results.

Also don’t assume your wheels even new are true. Have them check for wheel run out.

Good luck!

 

[cruiserdan]

Yup, I have DW and I'm leaving for a trip in two days. Wheel and trunion bearings are my only suspects.

It comes on at approximately 48 mph to approximately 52 mph and ALWAYS going straight. My GF drove the 80 without me in it and she pulls up to my house and asked me WTF is up with your 80

New panhard rid bushings, torqued hardware.
Tie rod ends are tight
Radius arm bushings are also new and hardware torqued.

That leaves two sets of bearings to check, should be easy.

Check the frame for cracks around the panhard brackets and steering box. My wife's truck had a crack in the frame at the left side panhard bracket. I had that welded up and her problem was solved.

 

[MMaxim]

My DW started after installing new to me tires and wheels. I bought them from a close friend and he said they were good to go, no balancing needed. I went ahead and replaced panhard bushings, radius arms bushings, tie rod ends, but DW was still there. So bad, actually, that the panhard rod mount cracked on the frame side.
Then I switched tires between two sets of rims and balanced both sets. No more death wobble even with 39.5" tires mounted on very heavy double beedlock Rock Monsters.

 

[cruiserdan]

Are you sure the wobble caused the crack and not the other way around?

 

[MMaxim]

Are you sure the wobble caused the crack and not the other way around?

Not 100%, but I was under my truck a lot replacing all bushings for a couple of weeks leading up to the discovery of that crack. Most likely would have noticed. Additionally, fixing the crack and reinforcing the mount did nothing to prevent DW.