Outer Limits 4x4 Board

Ok So my old diff was on its way out (clutch plate lsd type) got myself a low km helical lsd..

so I undo the 4 nuts holding the axles in place, pop them out, undo tailshaft, and diff nuts and drop the diff on the ground..

repeat process on my donor car

reverse process to put diff back in.

OMG those helical gear diffs are heavy!

so i go for a test drive and i hear this scraping sound coming from my rhs rear brake (like theres a bit of dirt or a rock in there) I figured the shoes must have gone back in a different position and its wearing a lip off the drum/shoe..

get back home, get under car, oil is &*(%$^*# EVERYWHERE!!

Both rear axle seals a spewing oil out all over the shop!

so i jack it up (for about the 500th time this week) and pull the wheels and drums off, (oil everywhere) i go to spin the axle and it moves, not round and round like it is supposed to (well it does that too) but in and out like 5-8mm worth of play!! check the other side.. same %#$%$ problem!

I dont understand!

could someone please please please tell me what went wrong? I am at my wits end here!

In the last week I have

-pulled original overheating engine out
-pulled engine from donor car
-installed replacement engine
-modified the wiring harness to suit new engine
-changed all the oils and fluids etc
-stuffed up (somehow) the rear axle..
-lost my mind a little
-wished i had sold it with the overheating engine and bought a brand new car that i cant afford
-etc!

Ok so my brother came round to give me a hand, swapped new LSD back into its original housing, bolted it all back in.. Tomorrow I bleed the brake lines and put oil in and cross fingers... Still hAve no idea what went wrong!

Anyone?

Anyway we swapped it all back into the donor housing, chopped the abs sensors off, and installed it into my truck.. So far all good. Still don't have any idea why it turned to poo the first time. Is it possible the backs pacing to the female spline on the diff centre is different? Putting strain on the brarings?