As Todd mentions, if this is an area your not familiar with, I also suggest someone else doing or at the VERY least helping you with the job.
Is it your third member, (the ring, pinion and side gears) or has your housing also suffered damage?
There really is no such thing as a temp fix. About the closest thing to it is buying a third member with high miles and getting it cheaper.
Heavier oil will prolong the issue at hand, but not if you already have an issue.
Also, just to confirm, it is the rear end, not the front end you need parts for, correct?
I just did a search and found some as low as $125.00 that were still worth buying. I found some at $99.00 but the have MEGA miles on them.
I also found several around the $200 range that had fairly low miles, right around 30 to 40 thousand miles.
Let me know...