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Unread 08-21-2014, 07:27 AM   #1
rjlaraway
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2005 TJ Wrangler 
 
Join Date: Nov 2012
Location: New York, NY
Posts: 48
Changing Speedo Gear

Dana 30/186MM Front Axle
3.07 Rear Axle Ratio
Dana M35/194MM Rear Axle
4.0L I6/Manual

Put 31x10.5 tires on with the existing 2" BB and noticed speedo is off, at 65 (confirmed by GPS app) it's actually 59-60 on the speedo.

Changing the gear looks pretty straight forward. I think this is the piece I need
http://www.quadratec.com/products/55200_6127.htm

Any advantage to going up or down a size here? It doesn't actually affect my gears correct? It's just a sensor for the speedo and odometer, right?

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Unread 08-21-2014, 07:44 AM   #2
bisleywrangler
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1997 TJ Wrangler 
 
Join Date: Dec 2013
Location: Gloucester, Gloucestershire
Posts: 50
There is no legal advantage in making your speedo read higher or lower than it should. Changing the gear will only affect the speedo and not the actual gearing of the axles.
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Unread 08-21-2014, 10:44 AM   #3
treemagnet
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2003 TJ Wrangler 
 
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Location: Montreal, Quebec
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The only thing u have done is change ur tires for larger than stock, so ur speedometer is reading faster by very little than what ur actual speed is. I would suggest not bothering to do this at this time
Wait till you decide to change ur gears to say 4.10 or 4.56 from the 3.07 then buy the correct one as now u would be paying twice for it. I did just that waited till i did my gears. As u cannot get a ticket for going
to slow normally but u can for overspeed.
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Unread 08-21-2014, 11:10 AM   #4
rjlaraway
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2005 TJ Wrangler 
 
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Location: New York, NY
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Quote:
Originally Posted by treemagnet View Post
The only thing u have done is change ur tires for larger than stock, so ur speedometer is reading faster by very little than what ur actual speed is. I would suggest not bothering to do this at this time
Wait till you decide to change ur gears to say 4.10 or 4.56 from the 3.07 then buy the correct one as now u would be paying twice for it. I did just that waited till i did my gears. As u cannot get a ticket for going
to slow normally but u can for overspeed.
Good point, out of curiosity what are the costs associated with going to 4.10 from 3.07?
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Unread 08-21-2014, 04:22 PM   #5
Knuckelhead
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2000 TJ Wrangler 
 
Join Date: Aug 2005
Location: Colorado
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Quote:
Originally Posted by rjlaraway View Post
Dana 30/186MM Front Axle
3.07 Rear Axle Ratio
Dana M35/194MM Rear Axle
4.0L I6/Manual
Put 31x10.5 tires on with the existing 2" BB and noticed speedo is off, at 65 (confirmed by GPS app) it's actually 59-60 on the speedo.
Changing the gear looks pretty straight forward. I think this is the piece I need
http://www.quadratec.com/products/55200_6127.htm
Any advantage to going up or down a size here? It doesn't actually affect my gears correct? It's just a sensor for the speedo and odometer, right?
Installing a speedometer gear 2 teeth smaller would get you close, 1 tooth equals approximately 3 mph at 60 mph on your speedometer. HTH
Quote:
Originally Posted by treemagnet View Post
The only thing u have done is change ur tires for larger than stock, so ur speedometer is reading faster by very little than what ur actual speed is.
I think you've got that backwards...
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Unread 08-21-2014, 05:58 PM   #6
2jhanna
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2002 TJ Wrangler 
 
Join Date: Jun 2007
Location: Denton County, TX
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OP, if you check out this thread below, you may can do a speedo gear swap for close to free, just shipping.

http://www.jeepforum.com/forum/f9/ta...o-gear-643981/
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Unread 08-21-2014, 07:30 PM   #7
sarkaukar2000
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2001 TJ Wrangler 
 
Join Date: Nov 2013
Location: , Texas Panhandle
Posts: 43
On the installation paperwork at the Quadratec site, a very important piece that gets missed at times.

Quote:
8. You will notice that there are a series of number located
along the side of the speedometer gear housing. Select the
appropriate tooth gear range you just installed and rotate it
until it is aligned with the raised dot on the transfer case as
shown in the picture to the left.
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