Might just do that thank youYou can swap from a E4OD to a AOD and keep your existing T-case.
You will need the Driveshafts, kickdown cable. shift linkage, PCM, and cross member to help complete the swap. If you have all those parts already then this swap will be easier then not. Would even be great to have a well documented swap from a meber here on the site.
However in my opinion, if you have to source parts then you might consider fixing the E4OD. I was working on swapping my E4OD for a C6 and I even purchased the parts to make the swap happen. In the end I still took my E4OD to the trans shop and had it repaired. Cost less in the end.
The E4OD is a decent transmission if you add a Transgo shift kit. Makes a big difference.The E4OD requires a computer, the AOD does not.(unless you are talking the AOD-E)
Though it may physically bolt in place the AOD will need a kick down cable ( I think can't remember)
Also I believe both transmissions used the 1356 transfercase so you should be good to go there.
I am assuming you have one just laying around? The AOD is kind of a backwards step.
E4OD is longer so drive shafts will need reworked and cross member moved.