Serious vibration problem with Disco1.... Need help/ideas/,....

[rollingstone]

Hi,

my name is Mike. I’m from Slovenia. I have been driving Landrovers for most of my adult life. I currently own Discovery 300 tdi auto. It developed weird problem after axle transplant....

So here it is. I fitted front and rear axles from a defender 90. Partially because mine were leaking diff oil everywhere, but mostly because the defender ones were fitted with ARB airlocks, HD halfshafts, 4.11 gears (or even higher, my speedo is now showing 60mph when I’m actually doing about 40) and castor corrected radius arms. The axles were fitted to a car as it would be to a defender, meaning no antiroll bars or steering damper...

I’ve also fitted front double cardan propshaft, rear 200tdi propshaft, and +2inch terrafirma springs and shocks.


Here’s my problem. When I’m doing certain speed on a road, car develops serius vibration. I shouldn’t really call it vibration, because it feels like the front of my car actually jumps from left to right. The vibration actually snapped my alternator cables off! I dont think this happens at the same speed every time, but it does happen when I go faster than 50mph.  The car is undrivable and dangerous. 

I did a run without front propshaft, and a run without the rear propshaft to see if any of the propshafts could cause this. No difference whatsoever.

I also did the tyre rotation/rebalansing. Also nothing.

 

Could a lack of antiroll bars caused this? The defeder the axles were fitted to before drove well.

Anyone ever experienced anything like this? What could have caused this?

[elbekko]

How much castor are the radius arms correcting? If they're meant for more than a 2 inch lift they could make the car very unstable...

Also, how are the panhard bushes?

[rollingstone]

Hi,

 

panhard bushes are new. In fact, all bushes have been replaced.  I'm not sure how much castor are radius arms correcting, I think 3 degrees, but will measure it today just to be on a sure side.

[FridgeFreezer]

This sounds like the famous / infamous death wobble and can be down to various worn parts, and probably not helped by modifications such as lifted suspension and steering damper removal.

There have been a LOT of threads and discussions of it over the years, I believe the common stuff to check first are all the bushes / linkages and the swivel kingpin preloads + wear.

[Bowie69]

If all the tyres are balanced/not full of mud, bushes are new, bolts are all tight, and bolt holes not worn out, then it is most likely your swivel pin preload, not a pleasant job but well worth getting right.

Don't try and mask it with better steering damper, it just won't work.

[Snagger]

I think Bowie has it.  I was going to suggest swivel bearings.  It could be wheel bearings or stub axles, though.

Jack the front of the vehicle up in a safe spot, and then try to rock the wheels holding the 3 and 9 o’clock position and then the 6 and 12 o’clock and feel for any play.  Then try it again with a helper pushing the brake pedal as hard as they can.  If you have play in both axis that disappears or reduced with the brakes on, it’s the wheel bearings and maybe worn stub axles (they can wear under the bearing inner races, so the bearings wobble about on the stubs, particularly common where oversize wheels and tyres and offsets rims or spacers have been used).  If the play is only in the vertical axis or the brakes have no effect, it’s the swivel pins and bearings.

The steering damper should be fitted, but it only assists smoothing the steering and don’t be tempted to fit a heavier damper to mask this fault - it doesn’t work because the wheels will still be wobbling in relation to the axle case and steering rods.Defenders do use steering dampers; it is just attached to the drag link instead of track rod.  Make sure you refit it.

You should not be using those altered radius arms without a lift kit.  It will be causing a significant geometry change of the steering, making it heavier and putting more strain on the steering system.  It shouldn’t cause any instability, though, as you have increased the castor angle rather than decrease it.  But it is incorrect if the car is at standard height.  It will also cause prop shaft vibration and premature UJ failures, even though you have eliminated this as a potential cause of the problem you currently have by driving with the prop removed.

In your position, I’d start by swapping the radius arms (and refitting the steering damper), and testing, then swapping the ends of you old axles (hubs and stubs on the rear, entire swivel housings on the front) to the new axles.

[smallfry]

Another vote for swivel bearings/bushes.

There are two different widths of the front radius arms at the axle end. No experience of getting this wrong myself, but could the narrow ones on a "wide" axle cause this ?

[FridgeFreezer]

4 hours ago, smallfry said:

There are two different widths of the front radius arms at the axle end. No experience of getting this wrong myself, but could the narrow ones on a "wide" axle cause this ?

The whole axle would be able to move sideways about 5mm on the bolts so yes I'd imagine it wouldn't help... but I'd really hope that would be spotted by anyone trying to fit the wrong arms

[rollingstone]

 

Same radius arms were on the defender also, and it drove well. Also, I do have lift kit installed. And I can't feel any play on the wheels.... 

 

I will try to  fit steering damper today, in addition to changing tie rods as they seem worn out.

 

Edited June 25, 2021 by rollingstone

[FridgeFreezer]

3 hours ago, rollingstone said:

Same radius arms were on the defender also, and it drove well.

But there are 2 different widths of radius arms - a narrow arm on an axle built for a wide one will move around.

[rollingstone]

 

Apparently new tie rods and steering damper did the trick.

 

Thanks a lot.

[FridgeFreezer]

Remember as others have said - steering damper does NOT fix the problem, it only hides the symptoms.

I hope the tie rods fixed it.