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Ecklers AutoMotive
Username Post: speedometer gear        (Topic#354794)
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-10-19 05:36 PM - Post#2757068    

I was messing with the 64 today and decided to check the speedo gear in the power glide. It's a 19 tooth gear and my speedometer is 10 MPH slow. I need a 16 tooth according to the TCI transmission websit but they don't have anything other than 19/20 tooth's. Per their sit each tooth is about 2mph taken away are added.
Does anybody know if there is even such a animal? If so could you be kind enough to post links so I can order one. I have found 17 tooth but no 16.

Thanks


1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


Edited by Andy4639 on 01-10-19 05:37 PM. Reason for edit: No reason given.

 
Ecklers AutoMotive
DZAUTO 
Senior Member
Posts: 8585

Loc: Mustang, OK, USA
Reg: 12-25-99
01-10-19 06:05 PM - Post#2757074    
    In response to Andy4639

There is not, and never was, a 16teeth plastic side gear. There are/were: 17, 18, 19, 20, 21, 22teeth gears.
The 17 teeth gears (GM part number 3987917-purple) are getting harder and harder to find.
The 18 teeth gears (GM part number 3987918-brown) are fairly common.



 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-10-19 06:15 PM - Post#2757075    
    In response to DZAUTO

  • DZAUTO Said:
There is not, and never was, a 16teeth plastic side gear. There are/were: 17, 18, 19, 20, 21, 22teeth gears.
The 17 teeth gears (GM part number 3987917-purple) are getting harder and harder to find.
The 18 teeth gears (GM part number 3987918-brown) are fairly common.



Thanks,
This is what I was thinking also since all the sits I checked today offered only the 17. I guess I'll order the 17 and get as close as I can.:toast:



1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
omarine 
Contributor
Posts: 185

Loc: San Diego
Reg: 06-29-15
01-11-19 11:55 AM - Post#2757129    
    In response to Andy4639

you could also get a sppedo corrector (I think it's called)

it screws into the trans, then the cable screws into the ratio corrector.

I got mine from Art Carr transmissions in Huntington Beach, CA. was like $75 I think.

they ask you for some #s - actual speed vs displayed speed at 20, 40, 60 mph if I recall correctly....

61 Impala bubbletop, 283, 2bbl Rochester, generator, points and drum brakes- daily driver
'49 Harley Davidson FL - Panhead


 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-11-19 01:09 PM - Post#2757130    
    In response to omarine

  • omarine Said:
you could also get a sppedo corrector (I think it's called)

it screws into the trans, then the cable screws into the ratio corrector.

I got mine from Art Carr transmissions in Huntington Beach, CA. was like $75 I think.

they ask you for some #s - actual speed vs displayed speed at 20, 40, 60 mph if I recall correctly....



Yes I have been looking into one of those also. Gear Ratio Adapter to speed your Speedometer up.
I'm going to order the 17 tooth gear first and see where it ends up at and then try one.



1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
62chevy427 
"12th Year" Silver Supporting Member
Posts: 2146
62chevy427
Loc: laurens sc
Reg: 04-13-06
01-11-19 05:05 PM - Post#2757150    
    In response to Andy4639

according to my experience,each tooth on the driven gear makes 4 -5 mph difference. you can also change the drive gear on the output shaft on the transmission.

56 bel air ((since 2002)
62 impala ss (since 1965)
65 el camino (since 1969)
66 nova (since 1987)
67 malibu convertible (since 1981)
72 el camino ss454 (since 1985)
83 gmc 4wd (since 1991)
95 impala (new)
14 camaro (new)


 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-11-19 06:56 PM - Post#2757163    
    In response to 62chevy427

  • 62chevy427 Said:
according to my experience,each tooth on the driven gear makes 4 -5 mph difference. you can also change the drive gear on the output shaft on the transmission.



I hope your right because I ordered the 17 tooth tonight. If it's that much I should be right on the money!


1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
64ausbelair 
Contributor
Posts: 271
64ausbelair
Loc: Australia (QLD)
Reg: 10-26-06
01-11-19 09:40 PM - Post#2757170    
    In response to Andy4639

I need to get a different gear on mine also. It reads about 73 when I’m actually doing about 63. (100 kmh here )
Less teeth increases speedo readout speed?



 
junky 
Valued Contributor
Posts: 2791

Loc: Northeast CT
Reg: 06-27-10
01-11-19 10:14 PM - Post#2757173    
    In response to 64ausbelair

From a post that I made about speedometer error correction last June.

http://www.tciauto.com/tc/speedometer-gear-c alcula... and I entered the number of teeth on the drive gear (8), the tire size P215-75-14, and that gave me tire diameter of 26.40 .. I entered all this information into the calculator, and it came back with "number of driven teeth" 20.223312268256087.

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-12-19 06:09 AM - Post#2757179    
    In response to junky

  • junky Said:
From a post that I made about speedometer error correction last June.

http://www.tciauto.com/tc/speedometer-gear-c alcula... and I entered the number of teeth on the drive gear (8), the tire size P215-75-14, and that gave me tire diameter of 26.40 .. I entered all this information into the calculator, and it came back with "number of driven teeth" 20.223312268256087.



I have questions on this:

1. How do you decide the driven gear inside the transmission? If it's out of the car I do but not when it's in the car.
2. What does the wheel diameter have to do with it? The tire diameter yes but the wheel it's part of the overall tire measurment???
3. Tire width, again what does this have to do with it?
I don't understand.
I called them (TCI) and talked with a CS guy and he told me what tooth count I needed. Which is 16 but there isn't such animal so I'm going for the 17 and call it good I hope.
I may get a gear ratio also later if the 17 doesn't do it.


1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
japete92 
"5th Year" Silver Supporting Member
Posts: 1121
japete92
Loc: No. Virginia
Reg: 01-18-13
01-12-19 06:57 AM - Post#2757184    
    In response to Andy4639

I would expect the rear gear ratio to be a significant (the most significant back the '60s) variable.

As noted by others, tire diameter would be another. But back when the cars were designed, tire diameters (as provided by GM) were not as 'variable' as those available/used today.

The state police used to (likely still do) get their car's speedo's calibrated every so often. There may be a procedure available some where.

Pete





 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-12-19 09:53 AM - Post#2757196    
    In response to japete92

  • japete92 Said:
I would expect the rear gear ratio to be a significant (the most significant back the '60s) variable.

As noted by others, tire diameter would be another. But back when the cars were designed, tire diameters (as provided by GM) were not as 'variable' as those available/used today.

The state police used to (likely still do) get their car's speedo's calibrated every so often. There may be a procedure available some where.

Pete





Yes there was a place locally that would calibrate your speedometer for you but they went out of business. Yes the size of the tires makes a more interesting challenge to get the right gear as well. Hopefully the 17 tooth gear does the trick.



1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
55Brodie 
Contributor
Posts: 236
55Brodie
Age: 66
Loc: Little River, SC
Reg: 12-26-15
01-12-19 11:45 AM - Post#2757202    
    In response to Andy4639

What you really need to know is the loaded radius of the rear tire.



 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-13-19 07:40 AM - Post#2757259    
    In response to 55Brodie

The measurement was with the car on the ground. 25" tall tires with weight of the car but no driver. He was doing the measuring!


1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
55Brodie 
Contributor
Posts: 236
55Brodie
Age: 66
Loc: Little River, SC
Reg: 12-26-15
01-13-19 09:55 AM - Post#2757269    
    In response to 64ausbelair

If your speedometer is reading "fast", you need to ADD more teeth to the driven gear. 73 ÷ 63 = approx. 1.16. Multiply that times the number of teeth you have now to arrive at the correct gear.



 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-13-19 10:32 AM - Post#2757270    
    In response to 55Brodie

  • 55Brodie Said:
If your speedometer is reading "fast", you need to ADD more teeth to the driven gear. 73 ÷ 63 = approx. 1.16. Multiply that times the number of teeth you have now to arrive at the correct gear.



Dang it, I knew I should have ordered the whole set of gears!

My speedometer says 64/65 but my GPS said 55. That's close, with holding a constant 65 is hard to do. According to what you said and the old gear is 19 now so that means a 22.04 gear is needed.


1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
55Brodie 
Contributor
Posts: 236
55Brodie
Age: 66
Loc: Little River, SC
Reg: 12-26-15
01-14-19 01:45 AM - Post#2757313    
    In response to Andy4639

I was responding to 64ausbelair, but yes, the math says 22 teeth for you.



Edited by 55Brodie on 01-14-19 01:50 AM. Reason for edit: No reason given.

 
Andy4639 
Frequent Contributor
Posts: 1258

Age: 58
Loc: Liberty, SC
Reg: 08-06-16
01-19-19 08:53 AM - Post#2757724    
    In response to 55Brodie

  • 55Brodie Said:
I was responding to 64ausbelair, but yes, the math says 22 teeth for you.



I ordered a 22 tooth this morning.


Been busy working on the 67 ramp truck.



1956 Bel Air - LT-1/4l60
1964 SS Impala -350 crate/powerglide
1967 Ramp truck - 350/ 4 speed
1971 C 10 - 6.0 LS / 4l80e 4:10 gears 30 years owner
94 Elderado
2000 S-10
2008 LTZ Tahoe
2011 Treverse


 
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