I have recently lowered my EL Fairmont Ghia with superlows all round. It now has a driveline vibration at approx 20km/h (shaking with every revolution of driveshaft) then hums at approx 80km/h. Now i suspect the pinion angle has changed, however i hear that the EL XR's have a different upper trailing arms (350mm compared to EL Falcons 320mm) Has any others had this same problem and did changing the upper trailing arms fix it, also did they have to be bolted on the rear holes on the diff? Now the driveshaft is perfecty straight and balanced, the UJ's are not old enough to be worn (12 months old) but the lower and upper trailing arm bushes may be worn but i dont want replace the upper arm bushes if i need the XR arms anyway.

Any help would be appreciated.

You can buy adjustable lower arms, to adjust pinion angles, not sure who from tho.

I was under the impression that the only difference was the XR items were boxed

I know that ef XRs had a trick bracket that the top arm bolted to on the body end, that moved the top arm backwards approx 10-25mm.
Also dont ELs have a number of different sets of holes in the top arm bracket? If yours does, try bolting through the forward most hole, to tilt the pinion up.

I've had slight vibrations and humming in my EF since i had my suspension redone a few motnhs ago. Funny thing is that the hum disappears in third, I.e it disappears when shifting back into third at 80km/h. Definitely has something to do with the height of the car cause its noticebly worse with a full tank of juice. I'd love to know how to fix the thing..

My diff does have 2 mounting holes on the top but already is attached to the forward hole. The rear one would bring the diff forward way too much. Anyways i have to raise the rear as Vic police gave me a "minor defect notice" It sunk 25mm lower than the spec of 350mm HTG This will improve the pinion angle but i will still look into the XR trailing arms.