Has anyone tried using a over drive unit in a BEC? They were once commonly used before 5 speed boxes incorporated an overdrive 5th gear. The one in a Triumph Spitfire dropped the engine revs by 25% when cruising on the motorway. I think that the units don't handle allot of torque so they were only usable in 3rd or 4th gear.

It might offer a way of running a low diff ratio without vibrating the car to bits on a motorway cruise.

Any thoughts?

One of Neds mates has a Hayabusa in his car with a normal car gearbox behind it for reverse.

Crucially though, this one is in back to front, so putting the car gearbox into third actually overdrives the output. Same effect.

Being a ford escort box, it's narrow enough to fit into the tunnel without the bellhousing.

Thats an idea! Does anyone have any idea how much the gearbox weighs?

Far too much! What are you doing on a motorway anyway!

With your helmet on you can't hear the engine that much. I think you are trying to solve a problem that doesn't really exist. At 70 in my blade car it was just over 7k revs. That's about right if you want any kind of response when you put your foot down.

Fair point Jubal - I might be trying to fix what isn't broken. I'm designing a 7 for track and road, looking for the power and weight advantage of a bike motor but don't want to make it too frenetic for the occasional road trip. As a long time biker I'm well used to the wind and vibes of a motorbike but I'm guessing that there must be a trade off between pulling away without frying the clutch and loosing your fillings on a cruise. I'll put a quiz together to see whether those who use their BECs on the road have any vibe problems.