speedo question, swap 140 for the stock 85 and now it's incorrect

It's right it just made your car much faster. :smartass:

Yes you do have to recalibrate it. I am not sure how, but I think you have to replace the transmission drive and driven gear...

That's what I've said to others. Never made sense that by swapping over the 85 speedo would make it automatically calibrated to the 140. You need to swap the speedo gears and tranny gears.

Ok, so does anyone know what drive and driven gear I will need. I have 3.73 gears

I've said this before and I will say it again......

You DO NOT change any gears anywhere when swapping speedometers. Speedometers are calibrated INTERNALLY. If you swap speedometers and now the new speedometer is way off, there is a problem with it. Fix it. Take it to a speedometer repair shop and have it calibrated.

Now, if you just bought a 140 MPH speedometer that you thought was a "real" 140 MPH speedometer but is in in fact an 85 MPH speedometer with a 140 MPH face, yes, of course it has to be calibrated for that 140 MPH face. Again, gears inside the transmission is NOT the proper way to do this. Calibrating the speedometer itself is.

So.....what exactly are we dealing with here? A "real" 140 MPH speedometer OR an 85 MPH speedometer with a 140 MPH face that hasn't been properly calibrated.

.:. Mustang Performance Parts - Brothers Performance .:.
They will recalibrate your gauge for 50 bucks.

Just installed a 140 cluster from LRS for 87-89 cars, in my 89 GT with 85mph. supposedly calibrated but horribly inaccurate.

What do you do in the case of Lazlos issue? Send it back to LRS and have them recalibrate it?

Ask Fox Chassis...

The speedometer is either not calibrated correctly OR the cable wasn't installed correctly or it and or the drive or driven gears are boogered up.