Getrag used an anaerobic sealant in their 3000GT and Dodge Stealth Transmission builds. An equivalent that can be used today is Permatex 51813.
Many of the transmissions we rebuild here have been rebuilt in the past at least once and its very common to see black, grey, or orange RTV sealant used instead of the anaerobic sealant.
The RTV sealant will seal up the transmission case, but there are some disadvantages. The #1 problem is excess RTV sealant will circulate through the transmission, clogging up synchros, hub/slider splines, and needle bearing oiling holes like the one below.
Anaerobic Sealant Advantage
The biggest advantage to the anaerobic sealant is that it will not cure in the presence of oxygen, so it only hardens in between the metal surfaces. Any excess sealant will be harmlessly carried away on your first trans fluid change, rather than hardening and clogging up the transmission.
The viscous coupling unit in the 3000GT and Dodge Stealth AWD cars is designed to limit the amount of slip between each axle set. It is a limited slip unit for the center differential. When they get old, or are abused by running with a broken output shaft, or towing with the car not on a flat bed they will leak out all of their viscous fluid. This fluid will often color the entire inside of the transmission black and contaminate everything in the trans. This is why its so important to clean every component and while you should not just replace parts that appear bad when taking the time to disassemble one of these transmissions.