proper speedo cable gear for C6 ?

[Kermit 460]

O.K. guys,

So just got my marti (have not posted it yet) originally my car had 351C with the FMX,it now has the 460 & C6 2.75 gears .I know my speedo is off without even checking it against anything.Does anyone with a C6 know the proper amount of teeth or color code for the plastic gear that goes in tranny to correct this setup ? :huh:

 

[c9zx]

Drive gear tooth count and circumference of the tire are variables you will need figure out. But, this link should help. http://npd.dirxion.com/WebProject.asp?BookCode=mtg12flx&archival=1&from=2# (go to page 158)

The revs per mile of the tire can be calculated or you can go to the Tire Rack site and look it up based on your tire size. Chuck

 

[Kermit 460]

Drive gear tooth count and circumference of the tire are variables you will need figure out. But, this link should help. http://npd.dirxion.com/WebProject.asp?BookCode=mtg12flx&archival=1&from=2# (go to page 158)

The revs per mile of the tire can be calculated or you can go to the Tire Rack site and look it up based on your tire size. Chuck

Thanks Chuck, much appreciated. Eric

 

[adm22]

When I changed my transmission the speedo was off. I reset the trip meter while passing a mile marker on the freeway. Then noticed what it registered when I passed the one ten miles later. Then figure out how much you are over or under. Then count the teeth in your gear and find figure out what the closest one that they make is to what the proper one should be. I dont recall the numbers but the best one for me was 1 less tooth than they actaully make- so had to go with the smallest one they had. So it is off by about 4% a lot better than the 25% it was off before. Chances are you will not get it exact but can get it close.

 

[Don C]

Here's some more information, the separate calibration box can be more accurate:

http://www.ringpinion.com/TechnicalHelp/ContentFrame.aspx?FilePath=~%2FContent%2FHowTo%2FGeneralInfo%2F%2FCalibarating_Spedometers.inc

And here is a lot of information, including a speedometer calculator:

http://www.transmissioncenter.net/speedometer_calibration_______va.htm?gclid=CO_4z7LF8rQCFUqoPAodZgoAkw

 

[Kermit 460]

When I changed my transmission the speedo was off. I reset the trip meter while passing a mile marker on the freeway. Then noticed what it registered when I passed the one ten miles later. Then figure out how much you are over or under. Then count the teeth in your gear and find figure out what the closest one that they make is to what the proper one should be. I dont recall the numbers but the best one for me was 1 less tooth than they actaully make- so had to go with the smallest one they had. So it is off by about 4% a lot better than the 25% it was off before. Chances are you will not get it exact but can get it close.

Thanks, I guess when it warms up I'll have to get in there to count the numer of teeth I actually have on the trans. & cable end ,then start doing some math.

 

[Flatback72]

When I put a NOS metric speedo in mine, using a GPS I found it was reading low by 5 kph (3.1 mph) across the range. Everywhere I read on the internet people were saying that altering the gearbox driven gear by one tooth will make a 3 to 3.5 mph difference - less teeth make the dial read faster and more teeth make the dial read slower.

So rather than use the calculations I decided that the gears were cheap enough on ebay, and managed to buy a group of 5 new driven gears each with a different amount of teeth for about $20 the lot. The first one I put in (one tooth smaller) gave me the exact 3.1mph that I was looking for.

So my opinion: first count the teeth on your current driven gear, then GPS test the speedo at a few different speeds across the range to work out how much it is out by and use 3 - 3.5 mph as a general guide as to how many teeth less or extra you will need, and maybe buy a couple of different gears like I did to give you a better chance of getting the right one.

 

[Kermit 460]

When I put a NOS metric speedo in mine, using a GPS I found it was reading low by 5 kph (3.1 mph) across the range. Everywhere I read on the internet people were saying that altering the gearbox driven gear by one tooth will make a 3 to 3.5 mph difference - less teeth make the dial read faster and more teeth make the dial read slower.

So rather than use the calculations I decided that the gears were cheap enough on ebay, and managed to buy a group of 5 new driven gears each with a different amount of teeth for about $20 the lot. The first one I put in (one tooth smaller) gave me the exact 3.1mph that I was looking for.

So my opinion: first count the teeth on your current driven gear, then GPS test the speedo at a few different speeds across the range to work out how much it is out by and use 3 - 3.5 mph as a general guide as to how many teeth less or extra you will need, and maybe buy a couple of different gears like I did to give you a better chance of getting the right one.

Thanks, I can borrow a gps ,give it a check then count the teeth.