P38 violent wheel wobble at 55mph

There’s vibration, then there’s death wobble - they don’t feel the same

When I first got my P38 it would death wobble fairly regularly. Death wobble (as opposed to vibration) you will know, it will feel like you're going to lose the front axle. If you brake to bring the speed down it will get worse, just take your foot off the pedal. Many times it gets triggered by hitting a small hole at speed, whereas things like unbalanced wheels just cause a vibration by hitting a particular speed.
As mentioned, replacing the steering damper is unlikely to help, in fact in my case changing it made it worse, as a PO had clearly found a good damper to mask the suspension issues (was old, and orange). Quick wins: wheel nuts (right size?), spigot rings (if you are not using P38 rims), wheel balance and looking for irregular tyre wear which might suggest toe/ tracking issues, and presumably tyres are a matching pair?
How old are your front suspension linkages? Recurrent death wobble will most likely have damaged TRE/ Drag link ends - your death wobble is new, but still worth checking. You can look at the anti roll bar links if they're old, but that wasn't my issue. Likewise shocks, are unlikely to solve the issue, I replaced mine cos they were toast, but it did nothing for the death wobble. Panhard rod/ bushes worth checking, but in my case the problem was poly-bushes fitted to the front radius arms by PO. Since I changed those back to stock I have never had any recurrence.

ouch... nice vid

Just a update, I changed track rod ends, link bar and steering damper, whilst under also replaced gearbox oil filter and gasket and oil, thanks for all your help, running great.

Nice one

Wow, I've heard all about it, but didn't realise exactly what it was, that vid shows it nicely.
Is there a definitive single cause, ie bushes, does it have several causes?
I'm guessing it's something finding the right harmonic frequency

Now we'll never know if it was the gearbox filter that did it )

kermit_rr said:

Wow, I've heard all about it, but didn't realise exactly what it was, that vid shows it nicely.
Is there a definitive single cause, ie bushes, does it have several causes?
I'm guessing it's something finding the right harmonic frequency

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Yes, I think you're right - mine would run quite happily 95% of the time, but a pothole at 55 mph was enough to start a lateral oscillation of the "right" frequency. I've read many people's solutions for death wobble and it seems to be different things for people (Radius arms, TREs. UJ's), although perhaps the severity of the death wobble varied in the first place. Polybushes on the radius arms is a definite no though, I've heard that from a bunch of others on other sites, and experienced it first hand. Mine also had a loose TRE on the drag link - hard to tell if it was cause or effect - but replacing it didn't improve the situation much

kermit_rr said:

Wow, I've heard all about it, but didn't realise exactly what it was, that vid shows it nicely.
Is there a definitive single cause, ie bushes, does it have several causes?
I'm guessing it's something finding the right harmonic frequency

Click to expand...

From what I gather it’s wear of bits all over, track rods, mounts, bushes etc depending on individual vehicle.

Sorta hits a resonance like harmonics. I’ve seen it on all sorts of worn 4x4s but only 4x4s.

Im getting a steering shake at about 70, feels like a wheel balance but just had them done, MOT advisory said lower ball joint mild wear, trying to find an Indy to get it changed, Im in Kent any recommendations.?

yelnats69 said:

Im getting a steering shake at about 70, feels like a wheel balance but just had them done, MOT advisory said lower ball joint mild wear, trying to find an Indy to get it changed, Im in Kent any recommendations.?

Click to expand...

Just because the garage said they balanced your wheels, doesn't mean they actually did, they did it right, or a weight hasn't fallen off. If it started happening when you had the balancing done then get it double checked. Mistakes can happen and weights can and do fall off.

Any Indy should be able to do that.

Can do it yourself with basic tools and the know off fellow members. Depends how hands on you are.

Thanks for the input, hands tied at the moment due to UK lockdown.