Very interesting post, I have only recently suffered the same failure of my Roverdrive (Roamerdrive early version), I use this unit almost exclusively for towing my 3 ton off road caravan using only 4th gear in my R380 gearbox. I spoke to ray at length prior to purchase about my intended use and if the overdrive was up to the task. Well nearly 12 years later I finally suffered an overheat failure as I missed seeing the temperature rise soon enough to prevent permanent damage.
It is possible I could have rebuilt the old unit but I decided to purchase a new unit with a modification that will include a low volume oil pump from the LT230 transfer case to the filler point of the Roamerdrive activated by a thermostat and an override switch when needed. The installation is almost complete with the only difficulty was having to make my own electric gear type oil pump as I could not find a suitable off the shelf one capable of delivering no more than 2 litres per minute and able to opperate at temps up to 110 degrees C. Please find photographs of my installation including an additional small round finned oil cooler that will give an additional 750ml of oil in the system.
I hope other can benefit from my modification as I have spoken to Ray and although he admits my modification will improve significantly the lubrication and temperature reductions he feels most users would never need these improvements, I will let you all be the judge of that but this post certainly would have benefited if this was in place before the damage shown. I do not see how I can upload my photographs so if someone can email me for help please.