Best diff ratio with a 6 speed zetec

[kenneth.mula]

Hello

I am trying to make the car more "road" friendly without killing the fun of it all. Our roads are twisty, slow (max 50mph)

The car is powered by a 2 liter zetec that has from 100 ft lb/2300rpm to 147ft lb/7600rpm. I have a6 speed caterham gearbox and my diff is 3.62.

I am thinking of changing the diff to an 3.38 ratio. I love the car in slow motion, cruising along with a smile on my face... and I like the fact that if I gear down it´l scream along quite happily..

If I change to the 3.38 my guess is that for the cruising the car will be much quieter, and if I do want to let it loose I still have 6 gears to choose from.

Any thoughs? Should I stay with the 3.62 (wich is a quiet one) or should I change to a longer 3.38?

I do not track the car, and if I would I think it still would be fast enough?

Kenneth

 

 

[Mark Durrant]

If you decide on a 3.38 I have a crown wheel and pinion for sale. Send me a message if your interested.

[Jonathan Kay]

Are you using a gearing calculator to do the comparison?

What will your engine speed be at 50 mph with the two final drives?

Jonathan

[paul jacobs]

Just keep the 3.6 diff, but knock the six speeder on the head.  The ratios are far too close for cruising and 6th is far too short, even with a 3.38 cwp, 

get hold of a standard 5 speed type 9, get BGH Geartec to put a longer 1st and 2nd into it and Bobs your uncle, a perfectly drivable and delightful Seven.

The point is, that 6 speeds does not make the gearbox right for the car.  Fine if it is to be used mainly on the track or hooning on the road, but as soon as you feel like cruising, you can't.  You want a top gear that will give you around 3500 revs at 80mph.  Use the Gearcalc calculator and see if I'm not right.  Just Google it.

[ScottR400D]

I agree, a 5 speed might be better for the OP, just on the road. 

Changing from 3.62 to 3.38 is going to drop revs by 2/300 at 70; not much difference.