Speedo Drive Location- Rover V8

[fairyglass]

Hi everyone, I'm a new V8 owner, and I hope you can help. I've bought a hot rod, which I'm making ready for the road. It's powered by a Rover V8 which I believe to be a 3.9l based on the engine number, with twin carburettors. It's mated to an automatic gearbox. The vehicle has no speedometer, which I'd like to remedy but in keeping with the age of the car I'd like ideally to go down the mechanical route.
I've read that Rover V8 gearboxes can have either a mechanical or electronic feed for a speedo. How do I go about identifying which I have, and where should I be looking? Access is quite tricky as the car is on air suspension and very low! I understand that I'll need to work out drive ratios to get an accurate reading, so perhaps there's a modern option that I could fit that would allow me to use an older speedo unit? All advice welcome- thanks in advance.

[ChrisJC]

Any idea what the transmission is from?

Generally, the speedo outputs come from just in front of the output flange, pointing towards the left hand side of the vehicle (facing forward).

The mechanical ones have a place to put a wire, and the electronic ones have a lucar terminal.

Chris.

[fairyglass]

Thanks Chris,
I'm pretty sure it's a Rover transmission- there doesn't seem to be any adaptor plate, the bellhousing bolts directly to the engine. I'll have a closer look where you suggest.
Cheers,
Ben

[GDCobra]

Photo would be a great idea.
Personally I'd go down the electronic route, much more flexible and should be possible to easily re-calibrate.

My car has a mechanical speedo but since building I've changed the 'box which has different speedo' gearing and the diff' ratio so now reads out, I'm currenlty looking at picking up the cable rotation via a sensor which I currently have fitted for triggering the ECU and then driving the mechanica speedo' with a motor. Hoping to have a way forward sorted soon.

[Ian Anderson]

Why not have the Gauge recalibrated?

https://www.speedycables.com/speedometer-calibration/

[GDCobra]

Why not have the Gauge recalibrated?

https://www.speedycables.com/speedometer-calibration/

Although I'm getting on quite well with my electronic/mechanical speedo' drive it is unforutnately taking place to several other projects so I may look into going this way myself. I fancy the electronic idea as it makes future modifications to driveline easy to recalibrate for but given that this is less likely going forward it may be more desirable to simply get it re-cal'd.

I've had a few dealings with Speedycables previously and always found them very good and efficient to work with so don't have any worries there.