Mike, like Phil mentioned, you'll need to ascertain what speedometer drive gear your transmission currently has. It's part of the governor assembly which is accessed by removing the transmission pan and the 4-bolt governor cover. Alternatively, perhaps Jim Burek can tell you what's in there. Once you know what you have, you can use the information at http://www.tciauto.com/tech_info/speedo_gears.htm to correct your speedometer.
One thing people always forget is that these old speedos are exactly that...very old. They are not very accurate and seem to vary quite a bit so this isnt an exact science..you need some magic in there as well. You know it was fast at several points....and you know what was in there so adjust from there...if it doesn't match the charts, oh well!! later Tim
Old/new cars can all be off. Even new cars can be off 2-3 mph at 65 mph. All they do is get as close as they can given the different gear combinations available.
The majority of new vehicles don't use speedo gears anymore. They use electronic vehicle speed sensors which output X pulses per revolution and the PCM then drives the speedometer based on the programmed tire size and gear ratio. Of course, changing these parameters means PCM reprogramming or else the readings are off just like old cars.
You can swap the drive gear , you need to go to more teeth than what you currently have. The driven gear for the 200-r4 is part of the governor and requires oil pan removal to change that. You can also put an adapter between the speedo cable and speedo hsg. Probably a .85 to .9 ratio would be a good start. Jim Burek
I put in the 43 tooth gear and my speed is right on now! Still doesn't make sense to me that the 43 gear is correct based on all the information. Thanks for your help. Tim
