What difference does overdrive make?

[Rich_s]

Hi Guys,

Still searching for a spitfire 1500 and have been offered one but it does not have overdrive, just wondered if anyone knows what difference it will make in terms of mpg, most of the driving it will do will be on motorways sitting at between 50 and 70, i know it will use more fuel as the revs will be higher, just wondered how much more though.

Thanks
Rich

[BrendanD]

The OD reduces your RPM by 20%. It allows you to drive at 70+ at the engine's most efficient point (4,000-4,500). It makes a lot more than a 20% difference in fuel consumption, decreases noise, engine wear and oil consumption. Its really 'essential' if you plan much motorway driving.

[Richard B]

932 wrote:

i know it will use more fuel as the revs will be higher, just wondered how much more though.

It will also cause more engine wear.

If you are going to do lots of high speed driving in it, budget on a conversion to O/D. Anything from £200- £900 depending if you're buying SH (eBay etc) or fully reconditioned from a supplier.

Gearbox inc O/D, Speedo angle-drive, propshaft, gearstick, switch, O/D mount & plate.

[Spitty2Dream4]

well.... i'm pretty new to spitfire ownership, by my 1500 has overdrive in 3rd and 4th. It drops the rev's by about 500rpm i think. I haven't worked out mpg yet as I'm still tinkering, but I'd expect you'd see more benefit on motorways.
After driving 5 and 6 speed cars, I find myself searching for a 5th gear in the spitty, I then remember that I have overdrive and it makes a huge difference... I really does provide an extra gear. Also, at town speeds of 30mph, I find that 3rd gear in overdrive is better then 4th gear out of overdrive.

[Paudman]

I used to drive the Gt6 around town in 3rd flicking O/D in and out at the steering column.... a very handy and lazy option for urban driving.
My current Herald 1200 rebuild goes from yes / no / yes / no / yes / no depending on my mood... if I can get the bits at Stafford this year I'll convert, if not... I'll probably regret it. It's brilliant for dual carriageway / motorway driving.

[Rich_s]

Thanks guys,

Thats what i needed to know, will definately only get one with O/D then, my daily commute round trip of 46miles is about 90% motorway so O/D will be a must.

Can't wait to get one now, currently drive an old mini 1000 auto and the motorway is not really the best place for it, hence why i am getting a spitfire, sucker for the old classics, can't help it. Trying to get descent info out of the mini owners clubs is not easy but your guys have been very helpfull so far so thank you all very much and will hopefully be able to help other people out in turn.

Thanks again

Rich