I've seen leaks where whoever put in the pinion seal did not fit it all the way into the recessed area before putting the metal retaining clip on. When they pushed the speedo gear in, it shifted the seal and a leak occurred. I've never had to use RTV to cover a seal leak on the housing. Simply put on fresh seals & applied a little dielectric grease (vaseline would work too) to the seal & pinion shaft. When inserting the gear into the housing, slowly insert it while turning it to keep the seal from moving out of place.
