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Username Post: speedometer gearing        (Topic#356559)
jrhopkins 
Poster
Posts: 39

Loc: washington state
Reg: 12-23-16
05-25-19 09:41 PM - Post#2767088    

I just removed the powerglide and installed a th350. the speedometer is reading way to fast. does anyone know the tooth count of the speedometer gear I would need for a 1960 Impala ?

thanks



 
Ecklers AutoMotive
GreatNorthWoods 
"5th Year" Silver Supporting Member
Posts: 1030
GreatNorthWoods
Age: 77
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
05-26-19 04:02 AM - Post#2767089    
    In response to jrhopkins

It is reading too fast because the new gear has too few teeth. Is the old PG still available? If so and if it is an aluminum PG, pull the old speedometer gear out. It will work in the TH350. If not, at least you can count the teeth on the old gear so you will know which TH350 gear to get. The gear you need will depend on what rear end ratio you have and what sized tires you are running. The older cast iron PG used a different speedometer gear.

Vern

1953 Chevy Belair Sport Coupe - 355 Blueprint Engine, 700-R4, Vintage Air, EZ Wire, Ididit column, Cruise/Tilt, 59 Vette Steering Wheel, 4-Wheel Disc Brakes, Posies Springs, Coker Radials, Nova 10-bolt, Mustang II front, Continental Kit


 
acardon 
Ultra Senior Member
Posts: 11272
acardon
Loc: DFW TEXAS
Reg: 03-25-05
05-26-19 07:10 AM - Post#2767094    
    In response to jrhopkins

Cast Iron power glide as used until 1962.
You will need to find out how many teeth are on the drive gear on the tail shaft, the rear end ratio, and tire size. Then size of the drive gear will vary, depending on what the transmission came from. The drive gears are color coded. Here's a calculator and the color codes. https://www.tciauto.com/speedometer-gear-calc ulato...

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
jrhopkins 
Poster
Posts: 39

Loc: washington state
Reg: 12-23-16
05-28-19 05:59 PM - Post#2767253    
    In response to GreatNorthWoods

I am using the speedometer gear that came out of the powerglide.



 
GreatNorthWoods 
"5th Year" Silver Supporting Member
Posts: 1030
GreatNorthWoods
Age: 77
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
05-29-19 05:27 AM - Post#2767272    
    In response to jrhopkins

If you are using the same driven gear that was in the PG and the speedometer still reads too fast, then the drive gear in the TH350 has a different number (fewer) of teeth than the PG. Looks like you have two choices. Change the drive gear in the TH350, or you might get away with using a driven gear with more teeth. How many miles per hour is it off and how many teeth does the current gear have? You can sometimes estimate what driven gear you need by increasing or decreasing the number of teeth by one for each 5 miles per hour it is off. I say sometimes because there can be instances where there is no gear with the number of teeth you need. I have been successful doing this in previous projects.

Vern

1953 Chevy Belair Sport Coupe - 355 Blueprint Engine, 700-R4, Vintage Air, EZ Wire, Ididit column, Cruise/Tilt, 59 Vette Steering Wheel, 4-Wheel Disc Brakes, Posies Springs, Coker Radials, Nova 10-bolt, Mustang II front, Continental Kit


 
stanski 
Poster
Posts: 71

Reg: 05-05-16
05-29-19 06:08 AM - Post#2767274    
    In response to acardon

The driven gear (plastic one) are colored according to the number of teeth. Grab a few different ones, get a speedo app on your phone, and just swap gears until you get as close as possible.



 
Ecklers AutoMotive
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