Speedo gear

[DmnStr8]

Yeah I know this question has been posted a zillion times and I did do a search I just want to check my answers.

My engine/tranny combo came from a 92. The previous owner put a set of 3.73s in, but neglected to fix the speedo. Since the car has only 62k on it I would like the odometer to be as accurate as possiable. In order to do this I need to put in a 7 tooth drive gear and and 21 tooth driven gear correct? I am running stock rims and tires.

I won't be doing this (don't have the know how or the place in order to drop the tranny) so anyone know or care to take a guess on how much this would cost me to have done at a dealership? I figure this will give me the high end of the price spectrum, I plan to look around.

Thanks and sorry for asking a repetitive question.

 

[_jb_]

check http://www.geocities.com/mgnedell/notchback/tech/speedo.html

 

[DmnStr8]

So I should go with a 6 tooth drive and an 18 tooth driven gear then? Thanks

 

[DW5.0L]

You need Ford part C4OZ-17271-A , Gear Speedometer. I just bought one from the dealer for my 3.73's.

 

[jrichker]

Rather than remove the aft end off the trans or pay someone else $$$ to do it, use a speedo gear correction adapter gearbox.

The stock range of speedo gears work correctly with a limited range of tire sizes.

See http://www.corral.net/tech/gearcalc.html for more help

Check to see if there is a speedometer shop in your area. If there is, ask about the Stewart-Warner speedometer gearbox. I believe it is either a 777 Series Drive Joint Kits and Parts or 666 Series Drive Joint Kits and Parts. It is a small gear box that fits between the speedo pickup gear on the transmission and the speedometer. It has quick change gears that allow you to choose almost any tire size and rear end gear ratio you want. This will allow you to get the accuracy with within 1%-3%.

Please excuse the typo (their's, not mine) in the following picture - it should read Custom ratio adapters, not Custom radio adapters.

See http://www.gaugeguys.com/ratioadapt.htm for more info.

 

[MrKwik]

Anybody know how many teeth the drive gear on a C4 has? Its like a 79 modelf that mate.

 

[DmnStr8]

Dropping the trans is not going to be a big issue, my mechs going to be down there to check another issue anyway. The egine/trans combo is from a 92 so I can't just change the driven gear.

Just checking before I order if the 6 tooth gear and the 18 tooth gear is what I want or if its the 7 and the 21. Thanks

 

[DmnStr8]

I went to stewart-warners site to look up the gear box you told me of (I am examining all the possibilities) but the link on the catolog wasn't functional. Any other place where I could learn about these as well. Thanks

 

[jrichker]

Check out the link to Gauge Guys, http://www.gaugeguys.com/ratioadapt.htm - it works. That's where I pulled the picture of the ratio adapters from.