big gearbox problem

Hi, looking for some help/advice. I have a Greg cabby gti. Driving home today accelerating onto a bypass my car started to grind and judder so pulled over had a look nothing looks wrong, engine running fine. So pull out again slowly it was ok till i hit 3000rpm and and it started again so had to have a toe. It engages all the gears and is fine under 2500rpm but any more then that and it seams like it shaking apart. The clutch has been slipping a bit lately but still had some life in it. Anyone had this befor? is it new gearbox time? its my daily car so i need to sort asap, any help would be great

Could be a fuel problem. Have you checked your filler neck for rust and or holes?

I've had fuel issues befor it feels very different the engine does not cut or lose revs

if ya cluth is slipping a bit ,it sounds like its time to take the gearbox off change the clucth (about £50 to £60)and get your gearbox cheacked, just had mine done new seals and bearings and the thrust bearing and end cap done to it £120 ,S&D transmissons doncaster 01302 739897,
the extra costs you could have would be CV boots or a drive shaft if one is no good !!!!!!!!good luck with it mate