240 turbo diff ratio-what are you running?

[heckflosse]

Questions coming thick and fast, I know.
What is the best diff for a 230 turbo'ed 245.I'm running a M46 box and at present a 3.9.
Due to the speedo woes Ive posted elsewhere on here, I want to swap in an earlier axle (with the metal diff cover, not alloy).
Ive got a 3.73 axle which would fit the bill nicely, but before I start grubbling around extracting axles, I'd like to know what others are running.
I think a 3.5 is a bit tall for our local roads in O/D.
Cheers, I'll get my anorak
Jim

[classicswede]

The 3.54 is ok but a little low geared for my liking. It is ok for local roads but too low geared for distance cruising. The 3.31 is better for distance and not really much loss on the lanes.

[Laird Scooby]

The 3.73 is a nice compromise round this neck of the woods between the long distance cruising of the 3.54 and the low geared "off the line" acceleration/torque of the 3.91.

It all depends what you want really, something that will fly off from the traffic light GP or cruise the A47 with lower revs. The 3.73 fits in between these two extremes.

The 3.31 is a bit too high geared for round here unless you're aiming purely for a cruiser but you will spend longer in the lower gears. As such any economy gains might be written off against having to use lower gears to maintain driveability, especially when you get stuck behind some numpty doing 38mph in a 60 and can't get past because of the traffic and bends.

[heckflosse]

Ive gone for the 3.7,mainly because we had an axle with that ratio and an early speedo pickup. Looking forward to driving the beastly thing one day!
Jim