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Username Post: Question on Transmission 200 4R        (Topic#366451)
pauldian 
Contributor
Posts: 420
pauldian
Loc: seligman,arizona
Reg: 05-14-09
09-19-21 11:46 AM - Post#2827407    

Question! What would a ( one ) tooth difference make on the driven gear on a speedometer in either m.p.h. or in a percentage. Does anyone know ?

Remember,I'm not always right. But I'M never WRONG !


 


grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17682
grumpyvette
Age: 73
Loc: FLORIDA USA
Reg: 03-16-01
09-19-21 11:55 AM - Post#2827408    
    In response to pauldian

http://garage.grumpysperformance.com/index.php?thr...

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
GreatNorthWoods 
"6th Year" Silver Supporting Member
Posts: 1317
GreatNorthWoods
Age: 79
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
09-22-21 01:51 AM - Post#2827664    
    In response to pauldian

From my own experience, one more tooth will decrease MPH by 4-5MPH. One less tooth will increase MPH by 4-5 MPH.


Vern

1953 Chevy Belair Sport Coupe - 355 Chevy V8, 700-R4, 4-wheel disc brakes, Ididit column, cruise/tilt,'59 Vette Steering Wheel, A/C

1930 DeSoto Business Coupe- 350 Chevy V8, EFI, 4-wheel disc brakes, Wire Wheels, TH400, S-10 Rear, A/C


 
paulo57509 
Senior Member
Posts: 537

Loc: CA
Reg: 07-18-00
09-22-21 02:47 PM - Post#2827713    
    In response to pauldian

There are gear calculators online. You'd have to know what you have in there now (drive and driven gear teeth), tire diameter and differential gear ratio.

You should be able to back into an answer.

1987 IROC-Z 5.0L
1992 Lumina Euro 3.1L
2003 GMC Safari


Edited by paulo57509 on 09-22-21 02:47 PM. Reason for edit: No reason given.

 
Rick_L 
Member #409
Posts: 27924
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
09-22-21 05:56 PM - Post#2827733    
    In response to paulo57509

On a 200-4R, there are effectively 2 speedo gears that you need to pay attention to. First one is the gear that's on the speedo output. That gear is similar to many other GM transmissions. Second one is the gear that drives it, which is on the governor assembly. I think all that's covered in the speedo gear article at TCI Transmissions website. Been a while since I've been there, hope it's still there.



 
65_Impala 
Very Senior Member
Posts: 4826

Reg: 12-29-02
09-23-21 08:53 AM - Post#2827780    
    In response to pauldian

If you know the number of teeth on the gear you currently have then it's a simple ratio. Say you have a 30 tooth gear. Going to 29 teeth would change the speed by 29/30 = 96.7%. Going to 31 teeth would change the speed by 103.3%.

The exact amount will change depending on the number of teeth on the gear you currently have so there is no simple fixed percentage answer. But the answer will always land in the 96-97% and 103-104% range so you could say changing a tooth would cause the speedometer reading to change by 3.5% which is likely close enough if you only need a single tooth change. I would calculate the ratio if you need a bigger adjustment.



 
pauldian 
Contributor
Posts: 420
pauldian
Loc: seligman,arizona
Reg: 05-14-09
09-23-21 09:44 AM - Post#2827789    
    In response to 65_Impala

I have the green 10 tooth drive gear and the 27 tooth driven gear which T.C.I. recommended and I'm still about 2 m.p.h slow on the speedometer. I ordered a 26 tooth gear and now I'll see where that go's. The closes one wins.....

Remember,I'm not always right. But I'M never WRONG !


 
GreatNorthWoods 
"6th Year" Silver Supporting Member
Posts: 1317
GreatNorthWoods
Age: 79
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
09-24-21 02:17 AM - Post#2827848    
    In response to pauldian

I think that will put you very close but maybe a hair over. You may not be able to get it exact.

Vern

1953 Chevy Belair Sport Coupe - 355 Chevy V8, 700-R4, 4-wheel disc brakes, Ididit column, cruise/tilt,'59 Vette Steering Wheel, A/C

1930 DeSoto Business Coupe- 350 Chevy V8, EFI, 4-wheel disc brakes, Wire Wheels, TH400, S-10 Rear, A/C


 
65_Impala 
Very Senior Member
Posts: 4826

Reg: 12-29-02
09-24-21 04:51 PM - Post#2827899    
    In response to pauldian

Say you are showing 58mph when running 60mpy so take 58 times 27 divided by 26 you get 60.2mph. Let un know what really happens.



 


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