Where can I get info on diff gears

[Mundy]

I have a 2004 TD5 disco and have and run 245/75/R16s (Cooper STTs). Means my tacho is out by 5% and worse, makes take-offs worse and can't ooze along as well as I'd like when I need to. I'm thinking of changing my diff gears or transfer case ratios. Does anyone know where I can get some info on what options are available and at what cost?

Mundy

[BigJon]

I don't think changing tyres wil make your tacho read incorrectly...:cool:. Perhaps you mean speedo and trip / odometer...

The small change you have made is basically not correctable with gearsets. A larger change in tyre size would require ratio changes.

[Slunnie]

It's probably cheaper to chip it so regain the power and improve performance, and to fit a truspeed to correct the speedo. You must be very sensitive to changes.

Diff gears are 3.54 standard. The Rover type options are 3.9, 4.1 and 4.7.

[Mundy]

I don't think changing tyres wil make your tacho read incorrectly...:cool:. Perhaps you mean speedo and trip / odometer...

The small change you have made is basically not correctable with gearsets. A larger change in tyre size would require ratio changes.

Yes, you are quite right, BigJon, not tacho but odometer and speedo. I was thinking one thing and writing another.

I have 'rechipped' with a BD do-over but at 750 to 1000RPM it makes little difference. Its great when the RPM is over 1500 and the turbo is spooled. Perhaps I'll wait to see what its like after I've done away with the EGR (soon).

Thanks for info on ratios, Slunnie.

Cheers
Mundy