Okay folks, here is a tough one. I am putting an aftermarket pulse sender into my C4 tranny (long story). Bottom line is it does not have a gear in the tail unit at this time. How many teeth do you think I should get for the plastic speedometer gear? I will be using a adjustable speedometer.

Thanks,

 

i thought the speedo gear was machined on the output shaft.
on this site there is a speedo calculator.
hope this helps

http://www.tciauto.com/Products/Tech...eedo_gears.asp

 

No, there is a worm gear on the output shaft and the plastic speedometer gear meshes with it when the unit is inserted into the hole on the tail shaft housing. Thanks for the help.

 

The worm gear is the speedometer drive gear.

It can have 6-7-8-or 9 teeth and is not replaceable.
As for driven gear specs you may have to experiment.

You will need, tire size, differential ratio & drive teeth count.

 

What if you have different size tires on the front and back? Also, it the number of gear teeth critical if the speedometer is programmable?

 

Unless it is not a 4wd there is no problem with different sizes front to back.

If the speedometer is programable it should not matter what the driven tooth count is.

 

That's what I thought. I am going with the mid range gear and see how it works.

Thanks for all the inputs. Very useful as always.