Just out of interest are you sure it has standard hight springs on it are the if not it may need castor correction ?
 
Update: Fitted new Monroe shocks last weekend. Car immediately felt better, took it over bumps which normally cause wobble and car felt good. However, during the week it has started to return, today 7 days later the wobble is back! Next plan is to replace Packard rod bushes with poly which was planned for last week but I did not want to carry out two jobs together.
 
Sorry for the slow update, I have been away for a while....
I changed the Panhard rod bushes to urethane items, the old ones were not worn or soft. I then took the car for a run and it felt no different.

Over the next week the car began to feel better with a noticeable change to the vibration/shaking. A week later the car is fine and I can now hit the bumps that caused problems previously at considerable speed with no shaking. I can however feel a very small tug on the steering wheel when going over the bumps. The previous death wobble has completely disappeared though, at long last! It seems that the new shocks needed to bed in for a while before the the problem stopped, strange but true.

In summary it appears that the wobble was caused by two sets of faulty shocks and a faulty steering damper.
Moral of this tale is do not buy Britpart Foam shocks or steering damper and if you do be prepared to change them in the near future. Please note that the car was not operated off road with these items, but the temperature here in Brunei is very hot and this may have effected them.
 
as a matter of interest, did you prime the shocks prior to fitting of both sets
Hi Johnlad,
Yes I did prime the shocks by fully compressing and extending about 6 times. I also diid this with the previous shocks I fitted. The car has been improving over the last two weeks and I can no longer detect any wobble or vibration at any speed. Great at long last.
 
Just like to say a big thanks to all who have posted replies to my issue. Lots of good advice was given and any one with a similar problem should be able to fix it by reviewing this thread. I think that there is possibly a lesson to be learned about buying non OEM parts such as Shocks and steering dampers. Buy a good well respected brand if you don't buy original equipment.
 
Hi All,
I don't know if anyone will see this update, but I thought it important to add some final closure. Not long after the last post the wobble came back, it was not so bad, so I changed the shocks again and fitted old man emu items. These felt great and the wobble all but disappeared for a quite a while. Then just a month ago it came back with a vengeance!
I found that the steering pump was leaking and replaced it, (bleeding the system afterwards as per the book). The next week the the steering got worse and worse, shaking hard at the slightest bump, until I felt car was unsafe to drive. I put the car up on ramps and went through the suspension checking every joint and bush, no play was evident anywhere. I then noted a small leak from the Steering pressure hose from the pump to the steering box. I pulled off the hose and replaced it, I carried out the bleed procedure and topped up the system. I took the car for a drive and it has never felt so good! I am left wondering if I have had a steering issue all along. Although I did rebuild the steering box once and then replaced it, making sure it was bleed properly every time.
All that I can say is that the car now feels secure and no sign of shaking. Nobody ever mentioned air in the steering, and its not something I ever thought about, but it will be first on the list if the problem ever returns.
 
Probably the reason that it wasn't mentioned is that there is usually a tell-tale screechy sound when air is in the hydraulic steering system, and you hadn't mentioned it.
 
I have only just picked up this thread and have nothing positive to contribute, except to say I spent many years in the Army and drove the MOD 110s all day every day.
They all ( We only got old ones ) did this. The REME response was its the steering giro, nothing can be done.
Pretty scary when you going down the Autobahn with your pedal on the floor.:eek::eek:
 
OK, a few years later but another update! The death wobble returned in 2016. Did a quick review of all the front steering and suspension mechanical parts for play and nothing found amiss. Steering pressure hose however found wet and was replaced. The system was bleed and the wobble went away. Some time later the wobble started again, this time the steering box output shaft seal was found leaking. Replaced steering box seal and bled system. Started engine and turned steering to full lock, where upon the output shaft seal promptly blew out past the circlip! Replaced steering box and bled again, all fine this time when trying lock to lock. I am not sure if the circlip was not in properly, or if the pressure relief valve in the pump jammed. The steering has felt light since this episode and I wonder if the relief valve is sticking. Maybe time to change pump.
 
The steering has felt light since this episode and I wonder if the relief valve is sticking. Maybe time to change pump.
I don't think you have said but I'm assuming your Disco is a D1, it must be because it has swivel bearings not ball joints ..............right?
The relief valve bleeds off pressure produced by the pump, if it was sticking, (I presume you mean in an open position), there would be less assistance i.e the steering would be heavier and not lighter, the valve should only operate in those instances where the steering is jammed on full lock or against a kerb or such, but from that you may deduce that your old steering box may have been a bit below par, the torque valving system in the power steering box is a bit complex and can produce some unusual symptoms.
Your original problem with the "shimmy" reminded me of my first Land Rover, an ex Australian Army, high ground clearance Series 2A, it was a terror on the highway at it's maximum speed of 90 Kph when you hit a bump and the steering wheel, (manual, not power assisted), would near rip your arms off, that was eventually totally cured with castor adjustment, not easy with semi elliptic springs but I made wedges for the spring mounts, problem no more. Worth a look maybe, someone earlier suggested castor correcting bushes?
 

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