speedometer gear

[roger gunter]

Can any one help
my speedomter is not reading correct
when my tach is showing 3ooo rpm everyone tell's me im doing about 70 mph
my speedometer shows 45 mph
anyone know what color and # of teeth I need for the speed gear (driven gear )
the driving gear in the tranny is white which is a 8 tooth gear ( I think )
I am running a Auto Meter tach which according to them, it is calibrated at the factory, and no calbration can be done in the field:evil

I have changed out the gear to a black 23 tooth and @3000rpm it showed 40 mph
changed it to a blue 21 tooth ( in now )@3000rpm showed45 mph

I guess I need to buy another gear, but not sure which way to go

any help would be appriciated

Ronnie
If you read this carbs are working fine now ( with the new spacers that solved all my problems)
heating was in my mind and not with the car

Even enjoyed driving the car yesterday even if it was just for 12 miles to check out the speedometer


Roger

 

[skipxt4]

????????

Roger: What size tires are you running? What type of transmission? And finally, what rear end gears are in the car? Can't help, without knowing these. Skip

 

[roger gunter]

skip
tire size is p235/60r15
gears are 356
tranny is muncie 252 low should not make any difference ( 4th gear is 1 to 1)
thanks
roger

 

[chevymusclecars]

Roger

I posted this before for someone who had the same question, I think you can answer the question there.

The attached web site has a lot of useful information that may help. The four speeds all had a final drive of 1:1 at that time and the only thing that changes the gear is the tire size and rear end ratio. By looking through the different charts you should be able to find the tire size, rear end ratio and color of the gear to find the number of teeth to give you accuracy in the speedometer.

http://www.teufert.net/speedo/speedo.htm

Bill

 

[roger gunter]

Bill
Thanks but that is no help
my tire size is not listed
according to other web sites , the old tire size is 26-91/4-15
not sure what the 91/4 would be ( e,f,g,h, etc. )
I emailed this guy about 3 weeks ago
he thought that the black gear 23 tooth was what I needed ( that is also what I thought )
anyway it isnt
I checked myu tach a little while ago with another meter
(tach point dwell)
the tach showed to be 200 rpms slower then the autometer tach
guess i will see if any one else has any imput
thanks
roger

 

[chevymusclecars]

Roger

Try this site.

http://www.enginebalancers.com/Products/TechInfo/speedo_gears.asp

Bill

 

[roger gunter]

Bill
thanks
still looking
according to their site I need a 36 tooth natural gear
according to my chart they do not make such a gear
the comp you sugested sells them, but they are caling them a 11/2 gear
I need a 3/4 inch gear
maybe im looking at everything wrong?
thanks
roger

 

[gbafus]

http://www.transmissioncenter.net/speedometer_calibration_______va.htm#Misc. Gears
http://www.bgsoflex.com/speedo1.html

 

[chevymusclecars]

Roger

Does the speedometer cable hook directly to the transmission or is there anything between it and the transmission?

Bill

 

[roger gunter]

straight to the transmission
I will call the local chevy dealer today and see if the part # I have is correct and if they sttill can get the gear
I have two choices
36 tooth # 1359270 or
15 tooth # 8642620
thats a very wide span between the two

one site I looked at yesterday said tahe 36 the other said the 15
thanks
roger

 

[skipxt4]

Speedo gear

Roger: Try a 22 tooth green gear. If that doesn't get your speed closer to normal, then try a 19 tooth white gear. You're probably never gonna get it perfect, but you can get it closer. Hope this helps. Skip

 

[Ronnie Russell]

My remedy. Put wife in her car with the cell phone. Follow her in your car. You with your own cell phone. Cruise the highway and tell wifey to set her speedo on 55 mph , She says, " okay honey, it's on 55",,,, check your tachometer,,,,,, Tell wifey to increase speed to 60 mph, check tachometer, repeat at 65 and 70 mph. Jot speed readings @ rpm on a note pad ,, Works for me.

 

[rstreet]

My remedy. Put wife in her car with the cell phone. Follow her in your car. You with your own cell phone. Cruise the highway and tell wifey to set her speedo on 55 mph , She says, " okay honey, it's on 55",,,, check your tachometer,,,,,, Tell wifey to increase speed to 60 mph, check tachometer, repeat at 65 and 70 mph. Jot speed readings @ rpm on a note pad ,, Works for me.

You're a lucky man Ronnie
Robert

 

[roger gunter]

Ronnie
If I put the wifey in her truck and had her drive 55
First she would call me on the phone and tell me about the big sale that was going on ,then shewould want me to check out her truck for a little noise she hears and no one else cah hear it
now we are doing about 65
she calls me and tells me about her day at work and she has decided to go over to another town and shop
O then she tells me to hav ea nice day and enjoy working on the car

roger

 

[oldskydog]

straight to the transmission
I will call the local chevy dealer today and see if the part # I have is correct and if they sttill can get the gear
I have two choices
36 tooth # 1359270 or
15 tooth # 8642620
thats a very wide span between the two

one site I looked at yesterday said tahe 36 the other said the 15
thanks
roger

Roger,
Have you looked into one of these? I recall they were used on high numerical ratio posi rears with 4 speed in some cars. 67-68 Camaro comes to mind but I haven't verified it.
http://cgi.ebay.com/ebaymotors/MUNC...9QQihZ006QQcategoryZ33733QQrdZ1QQcmdZViewItem

 

[Bungy]

Roger, Are you 100% sure your drive gear is an 8 tooth? Are you sure of the rear gears? Is the 3.56 a typo? sould it be 3.36? Anyway, here's a site that doesn't get any simpler. Plug in your tire size to get the diameter and then calculate the driven gear. Your info shows an 8 tooth drive and a 22 tooth driven. Also TH350 tranny gears are the same ones used in the Muncies.

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

You won't find a driven gear cheaper then this.

http://cgi.ebay.com/ebaymotors/SPEE...022106168QQcmdZViewItem?hash=item260022106168

 

[Bungy]

One more thing I forgot to mention. Your tach might be off. There is a switch inside to switch between 4-6-8 cylinders. It might be switched to the wrong setting.

 

[models916]

They even have ratio adapters

Near the bottom of the page. They carry all the speedo stuf you could want.




http://www.400raptor.com/?OVRAW=th400&OVKEY=th400&OVMTC=standard