Death wobble with FZJ80 axles on a Land Rover Discovery 1...any ideas?

[rrclassicbt550]

Hello,

I bought a Land Rover Discovery 1 with FZJ80 axles and I have a couple issues.

The first and biggest issue is a death wobble around 50ish, it is pretty violent but the wheel didn't seem to move as much as I thought it should for how violent it was. I noticed the steering rod running from the pitman arm to the knuckle is slightly bowed, but I am not convinced that would do it. Does anyone have any ideas? Supposedly the axles were completely rebuilt 28k ago. I have a suspicion that the vehicle was wheeled pretty hard since the body was "pristine" 28k ago, now it looks like a crumpled beer can. Not sure if that helps with the diagnosis, but I wanted to put it out there that it wasn't all highway miles.

The second issue is that when I engaged the front locker (ARB air locker) it took a little while for it to engage then when I went to disengage it, it WOULD NOT do it easily. It took quite a bit of forward, back, and turning to finally get it to disengage. Any ideas for a remedy? Or what the issue might be?

Should I just pull the axles apart and completely rebuild them again?

Thank you very much!
Jon

 

[MANUCHAO]

Possible bent axle?
Have you had a shop read your caster angles how much of a lift, if any?

 

[rrclassicbt550]

Hmm, I haven't checked that. I will give it a good inspection when I get a chance. Wouldn't that cause a wobble at any speed though? It drives pretty well up to about 35-40mph.

I have wondered about the caster. I believe it has just a 2 or 3 inch lift; however, the previous owner cut and fabricated/modified new/original suspension arms, so I am kind of thinking he would have addressed the caster issue. But who knows. Maybe he bent one of them.

I doubt it would have had this issue throughout the 28k miles. He drove up to/all around the article circle and then did some other adventures. It can't possibly have had this issue the whole time. So I am leaning toward something being bent or worn out. But everything feels pretty tight with no real play anywhere. Maybe he knocked the alignment out or bent something that could be effecting the caster.

Thank you, I really appreciate the advice!

Possible bent axle?
Have you had a shop read your caster angles how much of a lift, if any?

 

[MANUCHAO]

Have you checked wheel bearings for any play (lift the front axle and check for any play by pulling and pushing each wheel at 6 & 12 o'clock) in them? When was the axle rebuilt (bearings,gaskets, new grease) last? Tie rods tight? If caster was accomplished how did he get there?
Caster plates?
Caster bushings (these wear out and need replacing depending on usage).

I would get under the rig with a crow bar and make sure nothing is loose.... also a torque Wrench and make sure trunion bolts & nuts are up to spect..... the bottom nuts are known to come loose if you wheel hard....

Good luck...

 

[DaveInDenver]

Before assuming a major issue at least make sure everything is tight and solid. I'd also hit every bolt in the front end to make sure they are torqued and nothing has come loose.

Next step would be to at least service all the bearings, if not just replace. Bad wheel bearings or king pin bearings could be all it is. I agree, also check tie rod ends and that all rubber or poly bushings are still intact and snug.

Check tire balance and check alignment. Make sure you have enough caster.

You don't know the full history and people have different tolerances for issues. So it's hard to say it hasn't always had a bit of instability that has grown worse with worn components or as the tires aged. With all new parts perhaps it was mild and barely noticeable. People also used to mask steering misalignment with a new steering stabilizer.

In my experience a few years ago with them when an ARB is slow to disengage it was because it had backed up gear oil into the air side. In my case it was due to the seals and they would eventually push gear lube back into the solenoids and spit.

 

[lugueto]

It can be one of two things: Either the Toyota Axles want to break free from the LR Body/Chassis or the LR Body/Chassis wants to break free from the Toyota axles. This due to sacrilege.

Just kidding!

What I'd do is what DaveinDenver is suggesting, check all bolts and bushings first. Specially the ones where mounts had to be fabricated. I can't remember if the 80 has a bowed steering rod, but a few Toyotas do (FJ40s and 60s) so maybe the 80 one is as well?

 

[Stoffregen Motorsports]

Death wobble on a 4X4? Never heard of that before!!!

The most common causes of death wobble, at least on a Toyota axle, are

• not enough caster (depending on the vehicle, 4-6 degrees is ideal)
• too much backspacing on the wheels (wheel spacers count as added backspacing)
• loose wheel bearings
• loose trunion bearings
• incorrect toe setting

Other causes of death wobble are less intuitive

• shape of tire (crown of the tread surface)
• weight and size of tire (huge tires weigh more)
• bad tie rod ends
• loose u-bolts or other attachment points
• bad leaf spring bushings or control arm bushings
• too much rear weight on vehicle (lifting the front)
• loose steering box mesh or loose joints in the steering shaft
• loose pitman arm

The first group of causes are usually the things that actually cause the death wobble, while the second group can exacerbate a problem that exists elsewhere. I mentioned the shape of the tire. This is very hard to determine, but in my experience, a tire with more crown has more of a tendency towards death wobble. I used to work at a racing tire shop at Sears Point Raceway and my job was shaving tires. Crowning the tire was an art that had massive affect on how the car turned in and rotated through the turn. I have never gotten the chance to shave a truck tire that is known to have death wobble, but I would put good money on it that shaving less of a crown into a tire on a rig with death wobble, would cure it.

Start with the caster, wheel offset and maintenance items, but if your problem persists, you may need to try a different tire. On one rig I built years ago, I had to install two steering dampers to get the wobble to go away, so think of that as a possibility too.

 

[pnwcruiser]

You need the rest of the Land Cruiser to go back on the axles. Just Kidding! Hope these comments above helped sort it out. I've heard people fix it with a tire balance and double checking the lug nuts.