How fast am I really going

plumber1 · 07-21-2009, 10:17 AM

Well now that I got my 33's on and re-geared to 4:88 I have no idea how fast I going down the freeway. How hard is it to change out the speed-o gear to get it back to read correct ?

**timatoe** · 07-21-2009, 10:41 AM

Changing the speedo gear is at most a 5 minute job. The hardest part about it is seperating the $80 from your wallet. Here's a chart... http://www.jeep4x4center.com/jeep-speedometer-gears/index.htm

Looks like you'll need the 41 tooth gear. http://www.jeep4x4center.com/jeep-speedometer-gears/index.htm#41

Oh yeh, you'll need the short shaft one.

Here's a couple of quick little write ups. http://www.nagca.com/grandtech/speedometerregearing.htm and http://www.eriejeeppeople.com/Jeep_tech/misc_instructions/SpeedoGears.htm

**Louie4** · 07-21-2009, 10:50 AM

I'm planning on getting a new speedo gear after my 33's. I just regeared to 4.10's and I am still running 31's. So for now, I was driving on the highway behind my gf and just called her to ask how fast she was going. Now I just subtract 15 mph off the speedometer.

**foggybottombob** · 07-21-2009, 10:58 AM

Your speedo will not be off by a constant amount. It will be off by a percentage. The faster you go the greater the error in actual vs indicated speed. So at 30 mph actual speed your indicated speed will not be off by 15mph.

plumber1 · 07-21-2009, 10:59 AM

Timatoe, why did I already know it was going to cost me more $$ than I thought ti would. Welcome to the world of Jeep ownership. Thanks

**timatoe** · 07-21-2009, 12:05 PM

Quote:

Originally Posted by plumber1

Timatoe, why did I already know it was going to cost me more $$ than I thought ti would. Welcome to the world of Jeep ownership. Thanks

Check eBay too, I've bought two (used) gears in the past on there for well under $20 each.

plumber1 · 07-21-2009, 12:54 PM

Thanks will do, thats more like I want to spend

azgurney · 07-21-2009, 12:56 PM

Borrow someones gps and note the speeds on your speedometer verses the gps at various speeds.

**Louie4** · 07-21-2009, 02:10 PM

Quote:

Originally Posted by foggybottombob

Your speedo will not be off by a constant amount. It will be off by a percentage. The faster you go the greater the error in actual vs indicated speed. So at 30 mph actual speed your indicated speed will not be off by 15mph.

Yeah, I thought it would not be constant since its not linear with gearing involved. I think I remember reading about it on another thread too. I just suggested it because it was quick and its a little easier than taking a percentage for every speed.

Uberjeep · 07-21-2009, 03:05 PM

Quote:

Originally Posted by plumber1

Timatoe, why did I already know it was going to cost me more $$ than I thought ti would. Welcome to the world of Jeep ownership. Thanks

Or do what I did and go to a pick and pull yard, find the gear you need (they are almost always stamped with the tooth count on the gear) and swap it out in the parking lot with a 1/2" wrench in 5 minutes for $6 including the buck to get in the pick and pull yard.

**Louie4** · 07-21-2009, 03:44 PM

Quote:

Originally Posted by Uberjeep

Or do what I did and go to a pick and pull yard, find the gear you need (they are almost always stamped with the tooth count on the gear) and swap it out in the parking lot with a 1/2" wrench in 5 minutes for $6 including the buck to get in the pick and pull yard.

What vehicles were you pulling them from?

plumber1 · 07-21-2009, 04:34 PM

I was wondering the same thing, what do they come out of

**jay-h** · 07-21-2009, 08:03 PM

time the measured mile on the interstate. This will tell you how far you are off, both from gearing/tires as well as speedo innaccuracy. THEN calculate your new gear from that real world number.

**Mr-Rock** · 07-22-2009, 02:17 AM

Quote:

Originally Posted by azgurney

Borrow someones gps and note the speeds on your speedometer verses the gps at various speeds.

X2 on the GPS, this is the easy way!

Uberjeep · 07-22-2009, 04:54 PM

Quote:

Originally Posted by plumber1

I was wondering the same thing, what do they come out of

The speedo gears were identical in any of the jeeps I was grabbing them from that had a np231. All of the cheokees, and even some dodges that ran a 231. I had to go thru about a dozen to find the right tooth count for mine, but since it only takes a minute to pull the bolt and check the color of the speedo gear, then read the number to verify, it was a 20 minute process to find the right one. The clocking ring even has numbers printed on it so when you go to install, you just turn the notch to the right set of numbers (ie 27-35 tooth) and tighten up the bolt.