Outer Limits 4x4 Board

I've got a pickle of a question for you guys.

My folks discoverery has recently been shuddering quite violently. Its nothing to do with the tires or steering but is in the drivetrain. We suspect it could be the tourqe convertor/lockup mechanism in the auto gearbox that could be causing it, but neither Land Rover or Robinson Brothers have yet been able to fix it. We have been quoted roughly $1000 just to get the gearbox pulled out and looked at then put back in which is a bit much when we don't even know if the problem is in the transmission. The shuddering occurs between approximately 90-110km/h and seems to only occure on certain road surfaces. I believe that the spped and surface would have to do with the natural harmonics of the car amplifying the problem.

Is this common in the auto gearboxes in the Landrovers. The model is 1997 V8 SE discovery obviously with an auto gearbox and is fitted with BF All Terrains and King Spring standard ride hight springs.

One interesting note is that when we last gave the car a good workout over rough terrain it seemed to fix the problem for a while but it soon came back. Now, however we're looking for a more permanent solution.

Any help would be much appreciated.

...Have you had a look at the gearbox mount.....? On the 200Tdi diesels,
I'm told that failure of the pad leads to some funny symptoms...like idling
as if it was a 3-bearing engine....(jumping all over the place..!)

The V8 'll be smoother in this respect....but when you say it went away
after you gave the car a workout, makes me wonder if something did'nt just move sideways for a bit..?

Stuee,
Have you realy eliminated the tyres.
4WD wheel/tyres are large and exagerate any slight imbalance.
I would get them checked whilst fitted to the car.
I think it's called a static balance. Not sure though.

Check all the bushes, engine mounts, UJs and the rubber gizmo on the rear driveshaft before you spend too many $$$$ pulling things to bits

Ralf the RR
We've had the wheels and tyres balanced twice on the car so we are quite sure its not them. Some people have told us that when you change tyres you should also change the shocks. Our tires are slightly bigger and the springs give a slight lift also (10-15mm). Could not changing the shocks cause the vibration?

Cheers for other suggestions guys, i'll get dad to have a look at the things you mentioned lowbox and to check out the transmission mount to Nick.

Thanks for the help people and please keep those ideas coming.

Is the centre difflock really disengaged? It may be still locked and a faulty warning light not telling you so. The offroad workout would have allowed wheelslip and temporarily releived the torsional stresses in the driveline.
Bill.

Nah its not the centre diff lock. its not really that type of shudder. it starts off as a vibration and then increases into a shudder. It only occurs while going straight aswell.

If it happens when the truck is not moving - its the engine/gearbox mounts, it it happens while in motion, its either the UJs or bushings, or both.

Suggest you start by moving the front of the rig sideways (by pushing on the front end right above the headlights) and check whether there is a lot of play between the body and the axle (which should not move). That tests the panhard rod bushes, which fail prematurely due to a nice OEM leaky POS system.

Check rims and tires as well.

Hell, check the whole damn truck!

Check that you still have your harmonic balance (think thats what its called) on the rear of the engine. Its a round disc, about 150mm diameter, and about 30mm thick with a rubber bush in it. Mine had a bolt running through it and a "safety cable" running to the nut.

I have knocked mine off twice while 4 wheelin' and that causes a vibration in my 96 V8 Disco from about 60-90km under accelleration.

It is at the rear of the engine/drivers side, at the bottom so crawl in underneath.

good luck.

Ive removed the axle harmonic weight on 2 Discos with no ill effects. The rubber left behind is the same as the V8 engine mount- a spare-

I think the vib is in the drive shaft, rear, donut or uni?

Bazzle

Stuee,
Have you realy eliminated the tyres.
4WD wheel/tyres are large and exagerate any slight imbalance.
I would get them checked whilst fitted to the car.
I think it's called a static balance. Not sure though.

I apoligise ralf the rr. Turns out that the tires were never balanced on the car. When my old man took the disco to the place they were fitted (Bob Jane T-marts) they balanced them up nicely and rotated the wheels for us. Turns out the 4wd service centre dad went to before did a shocker of a job and even missed a tex screw in one of the tyres. And now from them rotating the tyres the source of the shudderng seems to now come from the back of the car rather than the front and due to the proper balance the shuddering has reduced dramatically. So now we are going to change the tyres around with the spare untill we eliminate the problematic tyre. Thanks everyone for your help.

Stuee,
Glad my advice helped.
Lucky the fix is "relatively" cheap.

just in case you haven't already checked..the front bushes on the rear trailing arms were worn badly on mine even though they looked ok from the outside & as a result the diff was swinging under load. replaced the bushes & had the tyres rebalanced (then replaced ..different story!) and the shudders went.