I'm just wondering is it possible to somehow get a speedo to read the speed from the tach isntead of the VSS on the tranny. I know it sound complicated but hooking up the speedo to the tranny is not an option so I figure if I can judge speed by RPM myself, shouldn't a gauge be able to do that as well...

 

I would not think you could convert your tach to work like a speedo. BUT you might be able to have someone drive next to you and figure out how fast you are going in relationship to your RPM's.

John

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You might be able to make it work, but say you calibrate it to read 65mph at 2000rpm, then it's going to read 65mph at 2000rpm, regardless of which gear you are in. For this reason, it won't work right, even if you can hook them together somehow.

 

Why is hooking the speedo up to the transmission not an option?

 

Like okfoz said, it's probably best to get on the highway in top gear, have a friend with a known good car and cell phone drive alongside or behind, and log your RPM at various speeds, say, from 40 to 80mph.

Also, remember that leaving transmission inefficiencies aside, double the RPM equals double the speed........ if you know that 2000RPM gets you 60mph, and you're driving along at 3000RPM, you know you're doing about 90.

If you don't have a friend to drive alongside you, get a passenger with a stopwatch, and record the time it takes to travel between highway mile markers; a mile per minute is exactly 60 miles per hour, of course.