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#1
12-15-2019, 05:32 PM
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Speedometer reads too fast.
Muncie 4sp. If I want to SLOW my speedometer reading, do I reduce the
Teeth ???? Thank you. |
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#2
12-15-2019, 05:34 PM
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No, you increase the teeth.
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#3
12-15-2019, 06:22 PM
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Quote:
__________________
 1969 Firebird 350 convertible, t-5, Carousel Red 2008 Solstice GXP 5speed manual, Sly 2008 Grand Prix, Ink Slate, Winter daily driver 2009 G8, Switchblade Silver, summer daily driver |
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#4
12-16-2019, 09:39 AM
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I've seen charts from doing an internet search that shows the teeth, and the number of MPH diff between each gear.
Remember, there are 2 drive gears, and each works within a range of driven gears. To change a drive you, you have to remove the output shaft and press on/off. The drive gears are not that tight of a fit, you can freeze/heat to aid with R&R. .
__________________
. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
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#5
12-16-2019, 12:27 PM
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Have bought gears from TCI, worked very well. They have a whole site showing how to determine what gear(s) you need and then a list for the gears they sell.
https://www.tciauto.com/speedometer-gear-calculator
__________________
"No replacement for displacement!" GTOAA--https://www.gtoaa.org/ |
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#6
12-16-2019, 05:16 PM
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Before you go to the trouble, make sure your error is linear. Use a GPS type app and a helper to operate your phone. Let's say the error is 70 indicated (on the speedometer) is 60 actual (on the GPS). If linear you should also find that 35 indicated is 30 actual. If this is how your speedo is operating then go ahead with the speedo gear change.
I once had a speedo that was dead on at 60 MPH. 30 indicated was about 38 actual. 75 indicated was around 70 actual. No gear changing would fix it at all speeds. Had to have the speedo overhauled.
__________________
My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
| The Following User Says Thank You to Bill Hanlon For This Useful Post: | ||
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#7
12-17-2019, 09:27 PM
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Thank you.
I changed my ring&pinion gear.
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#8
12-18-2019, 02:33 PM
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Taller rear tires would fix this also. I had tires replaced on my Jeep, told guy I wanted the stock size but he put slightly larger ones on and when I used my Garmin it showed my speedometer was reading slower.
__________________
“Nothing in the world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan Press On! has solved and always will solve the problems of the human race.” ― Calvin Coolidge |
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#9
12-18-2019, 03:17 PM
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The best option would probably be a converter box type of unit.
The gears in the tranny are sometimes never correct, and the combinations may entail a lot of work to get them to work. Some speedo gear combinations require different housings etc. 
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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#10
12-19-2019, 12:32 PM
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Changing tire size is only an option if you need new tires. Then, what if the correction is too little or too much.
The converter box works with the gears you have. It would be cheaper to just get the correct gear as long as you don't have to change the internal "drive gear". I have a box of gears that I have accumulated over 30+ years. I think I have every possible combination of drive and driven gears for GM manual transmissions. IIRC one tooth difference on the driven gear results in roughly 3 mph up or down on the speedometer.
__________________
1969 Firebird 350 convertible, t-5, Carousel Red 2008 Solstice GXP 5speed manual, Sly 2008 Grand Prix, Ink Slate, Winter daily driver 2009 G8, Switchblade Silver, summer daily driver |
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#11
12-24-2019, 06:25 PM
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I went from 17 tooth to 21. Satisfied with results.
Thank you all, Merry Christmas and seasons greetings. 🌲 |
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Linear Mode
