BARRACUDA1968
Well-Known Member
- Joined
- May 4, 2011
Anyone have a link to where I can get a speedo gear for 28" tall tire?
Speedo gear for 28" tire
- Thread starter BARRACUDA1968
- Start date
BARRACUDA1968
Well-Known Member
- Joined
- May 4, 2011
OK, how much will I be off from stock tire height?
BARRACUDA1968
Well-Known Member
- Joined
- May 4, 2011
Makes sense. One less thing to do.
You can get gears or add-on ratio adapters at www.transmissioncenter.net, but figuring out what you need can be complicated. Come to think of it, even finding where the stuff is on the site isn't easy (look for "Speedometer World").
TR Custom Parts
Mark Hueffman - Owner
- Joined
- May 25, 2001
http://www.tciauto.com/tc/speedometer-gear-calculator
Believe you can get the correct gear from GM, easy 10 minute job to change out. Can't remember what color gear I used, been a while. You would be changing the driven gear only.
Believe you can get the correct gear from GM, easy 10 minute job to change out. Can't remember what color gear I used, been a while. You would be changing the driven gear only.
How did you change the driven gear? Does it just pull out of trans once I remove the speedo cable ?
Once the speedo cable is disconnected at the transmission, there is a retainer bolt that needs to be removed--then the driven gear assembly basically pulls out. Have a pan handy, trans fluid will most likely come out depending on how you lift the car up to get under it....
Seems to me the black gear is correct for the 28" tire.
Thank you !!! ....you are correct, the black gear is for 28" tires
You can get the GM gear Part #'s here >> http://chevellestuff.net/tech/speedo.htm
Locate parts here >> http://www.partsvoice.com/ , here >> http://www.partszoneonline.com/index.php ,
or here >> http://www.transmissioncenter.net/speedometer_calibration_______va.htm
A Ratio Adapter may be available, you'll just need to figure out what % it is off.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm#gm ratio adapter
Calculators:
http://www.montess.org/speedo_gears.html
http://www.bgsoflex.com/speedo1.html
Locate parts here >> http://www.partsvoice.com/ , here >> http://www.partszoneonline.com/index.php ,
or here >> http://www.transmissioncenter.net/speedometer_calibration_______va.htm
A Ratio Adapter may be available, you'll just need to figure out what % it is off.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm#gm ratio adapter
Calculators:
http://www.montess.org/speedo_gears.html
http://www.bgsoflex.com/speedo1.html
All changes in speedo gear(s) need to be based on percent of the ratio of the two gears. With that said you need the exact tire height as it sits on the car and you can go on any of the online calculators and determine the gears you need. 10, 11, 12, and 13 tooth drive gears are available. The stock drive gear is 11 teeth. Use this info to determine what driven gear you need.
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About 6 mph at 60 mph I have 28" tall tires. Had a buddy drive beside me with a certified calibrated speedo (cop car).
26" tall tire 807 revolutions per mile
28" tall tire 747 revolutions per mile.
Try these:
http://www.f-body.org/gears/
http://www.wallaceracing.com/speedo-calculator.php
http://www.wallaceracing.com/Calculators.htm
Tire Info, rolling circumferences etc..
http://www.gnttype.org/techarea/suspension/Tirechart2.html
Trans Info. >> http://www.maliburacing.com/auto_tranny_id.htm
2004R gear ratios are:
1st = 2.74
2nd = 1.57
3rd = 1.00
4th = .67
Revolutions per mile will be a little different for each tire brand and series. Close, but not exactly the same. This is because the tires are constructed a little differently, and flex a little differently at speed (or even at different speeds, in different conditions).
So you get in the ballbark with gearing. But it's probably a waste of time calibrating your speedometer, if doing so is difficult, unless you plan on buying exactly the same tire every time forever.
So you get in the ballbark with gearing. But it's probably a waste of time calibrating your speedometer, if doing so is difficult, unless you plan on buying exactly the same tire every time forever.
This is why I suggested measuring the exact height with the tires installed in the car.
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