Forum:
I bought my current F78 in December. When pushing it a bit too much in second gear, there was a really strong vibration through the gas pedal - so much so it is almost like an electric shock. I then always made sure I changed up earlier. However about 4 weeks ago, I was doing just under 70mph and had a vibration through the gas pedal - not through the steering wheel, it disappeared just after 70mph. Unfortunately my No 1 fuel injector sheered off about 10 mins later. I had a new one made, but in hindsight I don't think it was fitted correctly. The following weekend, again just below 70mph had the vibration and again the No 1 fuel injector sheered off. I have now had another one fitted correctly and today put the vehicle into my local garage to find out what is causing the vibration. They couldn't find the cause. They think it could be the UV joints at either end of the prop shaft but as they were unsur, didn't want to go ahead and commit me to money and parts unnecessarily.
Does anyone have any idea what could cause this vibration?
Engine mounts.
Check the engine mounts. One could be broken or weak. A casual look is not sufficient - use a 'crow bar' or trolley jack to take the weight from the engine but take care where you support the engine.
engine mounts
They had already been checked - as per your method - and are ok.
lol
if that garage cant tell if you need new uj's on a prop dont go there cos they havnt got a clue, its simple, crawl under, have vehicle in gear, grab the prop and vigerously try to twist it both ways, if theres movement youll know about it. prop shafts need greasing quite regularly, especially if your doing those speeds in a fourtrak ( i wouldnt, to unstable).
Full of ideas but no time to do them!!
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youtube: Redfourtrack
Will get other half to do
Will get other half to do this! Very rarely do 70mph - only twice on motorway and not in 4wheel drive.
Prop Shaft
Did the previous owner remove and replace the prop shaft
If refitted in a different lug the prop will be unbalanced. The car will vibrate just like an unbalanced wheel.
I fixed a similar wobble with a jubilee clip. Fixed it around the prop shaft. A close look at the prop might show where it was balanced - front end or rear. It will take some time to get the balance correct because the jubilee clip will need to be repositioned until balance is achieved - repositioning forwards/backwards decreases/increased the weight. It the vibration proves worse then refit the jubilee clip a few degrees further around etc. Needs to be driven for every 'test'.
Apart from the previously
Apart from the previously mentioned, i would check the steering and suspension joints, these give vibrations at speed if worn.
Check the gearbox mountings along with the engine mountings, these also wear.
Check the wheels and tyres for damage and balance, even a lump of mud inside the wheel rim will throw the balance out.
Check the wheel bearings and rear axle input bearing for play, these often wear, especially the rears as people do not grease them.