I have not, but have heard the t14 is pretty simple to rebuild even for just the hobbyist. I have had a spicer 18 tcase apart which is pretty much the same as a 20 and it looked pretty simple as well and not to complex. I have not rebuilt a transmission or tcase yet but would not hesitate to attempt the 18 or 20 after having mine apart. I would get a manual and Just pay close attention to how things came apart and in what order.