Hey guys I've always had this issue with my EB I6 auto whenever I sit on 1400RPm the car feels like an earthquake it's so aggressive. I did the timing the other day (which isn't quite as accurate as it was before) and I noticed the vibration has been even more aggressive since, the car is on LPG only, the entire ignition system is brand new too. It's been serviced, I haven't had the gas serviced, maybe it just needs a tune? It only happens at 1400rpm it's fine everywhere else in the range.

Cheers.

Sounds like rooted harmonic balancer.

+1

Make sure you check the oil drains on the LPG converter......and check your harmonic balancer as previously mentioned.

Definitely sounds like a balance problem ,do you get the vibration in neutral or only when driving ?
If nothing in neutral revving to 1400 rpm check tail shaft & uni joints .
It does sound like harmonic balancer $95 new ,but will def vibrate revving in neutral

Hey guys I checked the balancer and it hasn't spun, is there anything else I should be looking for?

I noticed a clunking under takeoff today and jacked the car up to check the diff and spun the rear wheel, there's around 1-2cm of play before the other wheel starts spinning, would a stuffed diff cause this? Seems to use a lot of fuel too, I was amazed at how loose the rear wheels felt.

does it do it in neutral if you free rev it or only while driving??

Get if off the ground and unbolt the torque converter from the flex plate, Push the converter away from the flex plate and then start the engine and bring the revs up. see if it still does it.

Engine mount/s? mine had these symptoms untill one day it got so bad you could hardly drive and a big clunk after you let off the gas.
One mount completely broken off and the other had split and dropped the top under the bottom, never been quite the same.

It only seems to do it when driving, the entire car vibrates and it's loud lol, exactly like driving on a corrugated dirt road, it was no where near as bad as this a couple months back, it just felt like a tiny flatspot around 1400rpm, now it's doing it around 1200-1600 and like I said vibrates crazy. It's off the ground at the moment haha I have a spare 3:23 lsd I'm putting in because the current diff has almost 2cm of play in it! If a stuffed diff can cause this then I'd say that's it, it started clunking after take off a couple of days back, sounded like it was going to fall off the car, weird thing is I haven't heard any diff whine or anything close to it, it's stuffed though lol I can turn the tailshaft 1-2cm with the handbrake on and spin one wheel to the next wheel nut before the other one starts moving it's pretty loose.