The Dodge Challenger Message Board

Would it be possible to use stock miles per hour speedometer to display kilometers per hour by playing with speedometer gear on transmission? That would require spinning wire at 1.6 times as fast as normally of course..

Interesting question.

I guess it might be possible.

Lets start with what gear you need to read correct mph. Then go from there.

So what are your rear tyre and gear sizes?

Tyres are 245/60R15 and rear-end 2.76. Today speedo displays exactly correct MPHs so obviously gear suits my rear-end ratio and tyre size. No idea how many teeths there.

So you must have something like a 27 tooth speedo gear wheel in there.

Mmm.

So you would need something like a 17 tooth gear to make the speedo 1.6 times faster?

Not sure one exists.

So I suspect you would need to change the speedometer.

The Euro Challengers came with Km speedos. Or at least both mph and Km on the same face.
Were they calibrated different or was the face of the instrument just marked differently?

You could just fit low gears in your rear axle!

Something around 4.40:1 should do it.

dave-r wrote:The Euro Challengers came with Km speedos. Or at least both mph and Km on the same face.
Were they calibrated different or was the face of the instrument just marked differently?

Wouldn't odometer be still in miles if just face is replaced? Odometer gear inside speedo needs to be different at least.

TCI page lists 25 as smallest speedo gear.
http://www.tciauto.com/Products/TechInf ... _gears.asp

I also found adapters to speed-up and slow-down speedo cable from PATC. Search for "speed up" on http://www.transmissionhead.com/

Going to 4.40 on rear.. Might not be that good idea after all.