Disco 2 Vibrating under hard acceleration.

May I please ask if anyone has an idea what could have happened.
The car is a Series 2 V8 Thor engine. Yesterday I had to pull off a fast A road and accelerating back into fast traffic there were a few seconds of really rough running and vibration right through the car. It picked up and ran perfectly for the rest of the trip at motorway speeds, on B roads and accelerated cleanly from roundabouts and traffic lights as its always done. Happened again on the return trip on another A road when I pulled out of a petrol station again trying to get up to speed in traffic. Ran perfectly okay all the way home.
Not sure if it's engine, transmission or running gear. The only issue I've had that was similar with it was when the front prop collapsed but thankfully at low speeds. That naturally was rough running till it ground to a halt.
Any advice or ideas should be gratefully received. Thank you.

Does it happen on a certain rpm range? Like on mine I have some resonance between 2700-3000rpm undependent of in which gear the car is.
In my case it seems that comes from drum brake....

berg450 said:

Does it happen on a certain rpm range? Like on mine I have some resonance between 2700-3000rpm undependent of in which gear the car is.
In my case it seems that comes from drum brake....

Click to expand...

No, one it's never done it before and I was more interested in looking at the road than the dash. It was full throttle I was using, I naturally backed off the accelerator till it felt smooth again. Then normal throttle.To be honest it felt more running gear/transmission than engine but could be wrong. By the way it's not on LPG just petrol. I know instead of asking I should get under it and look at both props. Try to do that tomorrow if the weather holds. But thank you.