vibration when running at speed


hi guys, looking for some advice before i spend money, got a viration sunndenly appeared on the fourtrack, at tickover and on acceleration, rear prop is new, well was 1000 miles ago and joints are greased without movement, tyres are ok, bus just passed its ticket as well, vibration seemed to come together with changing tyres to a more aggressive tread, however when you take your foot off the throttle it stops, been under it and one thing i have noticed is the transfeer box bobbin has let loose and the bottom , its still there but what i am seeing is the bobbin is 1/2 way over from the plate but the rubber is not distorted, the gearbox mount seems to be still in place, what i am wondering is is there an adjustment in the gearbox mount that can be made to correct the offset i am seeing or is there something i am missing thats causing this, also the clearance between the crossmember and the trans box seems to be very little

any help appreciated


Check the engine mountings, these often split and they are not visible unless a large bar is inserted to prise the engine up.

Check the wheels and tyres, when the tyres were changed, have you checked the wheel nuts after 50 miles, they may be loose. Aggressive treads may pick up large amounts of debris, this may be causing the problem, as may a wheel balancing weight knocked off. Check the wheels are not distorted, damage such as this may occur from hitting a pothole on road, or from heavy off roading.

On the gearbox crossmember the mounting hole is a slot, this will allow the gearbox to move over slightly.


Check all the items mentioned and also the carcass of the tyres. I have had new tyres where the carcas has failed within a very short period. I refer to the tread rather than the walls, although you should check the walls as well. This often produces just a slight hump in the tread, barely noticable to the eye, run your hands around the tread and if you fell a bit of a hump it is likely that the carcass has failed. It causes the vibration and the hump will wear ver quickly. It is obviously caused by failure of the carcas beneath the tread itself but the tyre seller will insist that you have done it in a pothole or on a kerb. If found during an MOT then it is a fail but I stress if found and it can happen at anytime to a perfectly looking sound tyre.

Aggresive tyre also transmit a lot of vibration. I have an old Land Rover with MT Extra Traction tyres on and they strip your speed, are noisy and the vibration is terrible and wosten the faster you go, if 50 is fast. The may look great but are a pain. You may have seen(Heard)convoys of Army Land Rovers and heard the noise from such tyres, well those lads must have been half deaf at the end of a long haul and when I brought my landy down from Glasgow I could feel the vibration in my legs for hours after.

There is also a theory that balancing on new tyres should be re checked after the tyre have completed 1000 miles once they have "bedded in".


M J Young