Thanks,Overdriven! I have one more diff that I can swap into an alloy case.There are a few diffs on Ebay,also.I have the early differentials without the spider gear brace.I tried the Teflon shims and you are correct,the shims get eaten alive in there!
Testing yesterday,the gear mesh went WAY away.It will have to come out,again.
Maybe this one:
https://www.ebay.com/itm/Traxxas-1-1....c100005.m1851