If you get a chance do the coast thing again in neutral first and see if it does it.
How long ago was it rebuilt? Have you checked the diff fluid? Something inexpensive you could try, is to put some friction modifier in the diff. Not gear oil with modifier in it, but straight modifier. I don't know if it will help, but if it doesn't have or have enough modifier in it it might give you that lurchy feeling. Again, it's just a guess but something you can try that doesn't cost an arm and leg.
I know when I rebuilt my center section it felt like a spool when turning for a bit, catch and release catch and release.