How many Teeth do I need...........

you were expecting a Kentucky joke, weren't you ??

What I need to know is, how many teeth do I need on the Speedo Gear for a 3.70 rear gear and a muncie 4 speed ??


I can not believe the people who sell the gears can not recommend the correct gear based on that info. One place wants to put the car on a dyno to figure it out.


I just want to be able to do this :3gears: without worring about the police doing this :spank:

 

MIght this helpo No:

http://www.bgsoflex.com/speedo1.html

Basically, type in your tire Dia., Rear gear info, and pull the Speedo drivin gear to see how many teeth are on them, then it will tell you what the other gear is supposed to be

 

well, thank you, now I just have to find a way to count the teeth on the drive gear

 

LOL.... Good luck, I was under there on a TH400 for 40min, I kept getting a different count. I figured I was good if I got the same number 3 times in a rowou:

Is there a Muncie web site or tech article that might have the info??

 

I was hoping there would be

 

Donny:

If you can't find what you're looking for, you might try asking over at www.yenko.net, as it's come up a couple times before in the past...

 

I found a post buried on a web site with a guy who has an olds with 19 drive teeth.

you can figure out the drive teeth if you know the Drivin teeth...

Just type in your OLD values from when the speedo was correct before the changes.

Like if you had a 3.08 rear with 28in tires, and a 40 tooth drivin gear, that will tell you the Drive gear teeth, then use that figure with the New info to get the Drivin teeth number you need.

Of course, it only works that way if the old parts were correct to begin withou:

 

they were,


but


I changed rear ends and transmissions, so no telling in the old trans has the same gear as the new trans......

 

..... and that's precisely why the people selling the speedo gears can't tell you which one you need.

 

So, they could not sell me a set ?

 

Sounds like your best bet is just to throw it together, then take it to a trans shop. There is one down here that will drive it... Find out exactly how far off the speedo is, then make a reducer box the goes where the speedo cable plugs into the trans. Like $75, but its better than pulling your trans just to count teeth.... Unless, you need the correct appearance.

If you have to count, then I'd get a mirror on a telescoping rod (kinda like a Roach clip but with a mirror), then get in there with a chalk stick, mark a tooth, and count. It helps for your third or fourth hand to be holding a flashlight too.... ou:

 

Don: there a place on Woodward in Royal Oak called Specmo. They can help you out. I bet you will have to take the car there, but ~maybe~ they can do it over the phone if you can provide the info needed. The police use them to Officially Calibrate their speedos. Specmo is between 12 and 14 Mile Rds.

 

Donny, if this is for a GM car, just chuggle over to the GM counter. There is a specific and clear chart for this in the GM books. They have everything listed based on tire size, trans option and rear-end ratio. From that, you pick the correct trans adapter, driven gear and drive gear from the chart. It's very simple, i've done it a bunch of times myself. I did it on Mighty Mouse with 4.56 gears, G70-14 tires and T350 tranny, and it's reading is almost dead accurate.

HTH...

J