Did he replace the complete housing, caliper to caliper? If he did, it sounds to me like you could have an EF diff, I'm not sure without pix. of the bolt holes. EF has only one hole, EL has three.
At super low height the diff pinion angle is usually way too high, causing massive vibration and thumping and needs adjusting, you [or he] may have to fit Ef arms to correct the problem. s**t mechanic if he can't see the pinions out of alignment, if that's the case.
My EL diff is a T6AC, ie T6 series, it's in an EB and needed adjusting to stop the same symptoms you have. BenJ's EF diff is a T4AC.. T4 series.
I've attached some pix for you to compare the bolt holes and for the pinion angle before and after I corrected it, have a look here:-
http://www.fordmods.com/forums/el-xr6-d ... 59213.html
Sounds like he may be under the mistaken impression that EF and EL diff housings are directly interchangeable.
Cheers,
Paul

 

 

Attachments:

IMG_0128 (Small).jpg [ 61.3 KiB | Viewed 141 times ]

IMG_0126 (Small).jpg [ 70.09 KiB | Viewed 144 times ]

paulmac has hit the nail on the head!
thats the same problem i had with fitting a ed diff into my ea....ed has 2 holes..
and yes if the top arms are in the wrong holes the car will vibrate and the tail shaft will hit the floor..
also im pretty sure ef top arms are a different length to el ect?

yep ef diff ,my a/m panhard thingy doesnt fit no more ,they gave me my old diff along with freshly bent tone wheels and a 75% refund but refused to fix the issue ,ended up 6 mechanics looked at it before he would accept fault ,and the mechanic not the boss still swears its not his doing.
you can actually see the diff sagging down ,and my sway bar doesnt match up. i am now going to get new slotted discs,bearings ,diffbearings, and since i cant re rego my car now it will give me a chance to do it properly. i will paint the thing aswell.
any other sugestions on things i should get my mechanic to replace while i have it out ??pics tonight

and i forgot thanx for all your help guyz its amazing what a bit of info behind you can do.