Speed and RPM indicator

[pete jackson]

Just a small question for the more technical minded.

What speed should your 2.5 be travelling at in 4th gear overdrive with a 3.45 diff, 25% higher ratio gearbox and rev-counter reading 4700rpm?

Reason for question is that I don't think my speedo is reading correctly with 195/60/14 tyres. 

The needle was pointing at my left foot 🤣 

[JohnD]

You need to say what is the overdrive ratio. Or, what type of O/d you have.  And what is a "25% higher ratio gearbox"?
Pointing at your left foot sounds like zero.

Edited February 12 by JohnD

[Clive]

http://www.mintylamb.co.uk/gearspeed/

Use that site, put in all the correct parameters etc.

If unsure, top gear no overdrive is always one to one, so can remove the different OD options. 

[Adrian Girling]

At a steady speed on a straight road a satnav will give you a speed reading which is probably more accurate than your speedometer.  Typically speedometers over estimate the speed to keep within the law. 

[pete jackson]

21 hours ago, Clive said:

http://www.mintylamb.co.uk/gearspeed/

Use that site, put in all the correct parameters etc.

If unsure, top gear no overdrive is always one to one, so can remove the different OD options. 

Thanks Clive, I think I must have been at max speed for going up a hill, I should really get this one on the dyno 🤣