If you are really enterprising, you could mount a reverse switch to the end of your transmission. Anytime the clutch is engaged, the OD shifts to low. You could also put it on the clutch, which would be more useful, I think. Anytime the brake is engaged, the OD shifts back to low. I may add a brake or clutch over-ride as well. Maximum Overdrive has a schematic for a brake override to protect the OD. I have a dash light that reminds me when it is on. There are a lot of warnings about putting them into reverse, so I'm going out of my way to see that it doesn't happen. I have two units and both seem pretty solid. I've never heard of anyone blowing one up.
It is possible that the clutch material may wear out. The gears are pretty much bullet proof, unless they are sheared off by a load, and it would have to be a really big load. There just isn't much to these units, and not much to go wrong unless you put the seals in incorrectly-generally, either the electric solenoid goes bad, or the hydrauling unit needs the o-ring kit. If you get the o-ring kit, you'll also get some very nice images of how to rebuild the OD.
