Jeep Wrangler Forum

Jeep Wrangler Forum (
-   TJ General Discussion Forum (
-   -   Speedometer Readings v. Actual Speed with 33's (

pekoe1111 06-10-2013 01:31 PM

Speedometer Readings v. Actual Speed with 33's
Just bought a 2004 LJ with 4.88 gears and 33s. On the seven hour drive home, I stuck to 70mph on the speedo, knowing that it can be off by as much as 10 mph. Today, I used an iPhone with a GPS speedometer app. and this is what I found:

80 mph on the speedo = 65 mph!
70 mph on the speedo = 60 mph

Can't remember the rest...

What are your readings v. actual?

JeepReaper09 06-10-2013 01:59 PM

I just threw my 33s on with 3:73 gears and my speedo is off roughly 8-10 mph. So when my speedometer shows 60 I'm doing about 68-70 mph.

RevCo666 06-10-2013 02:00 PM

Driving on 31's, my speedo reading was off by about 2-3% so it wasn't worth replacing the speedo gear. Where as if I was in your shoes, that would be priority one to change asap.

Jerry Bransford 06-10-2013 02:06 PM

Why not just install a new 42 tooth speedometer gear so your speedometer is accurate again? It only take 5 minutes or so to replace it.

JeepDrum 06-10-2013 02:25 PM

I'm having the same problem, but I haven't compared with a gps to get an estimate of the difference yet. Can't a procal fix this?

Jerry Bransford 06-10-2013 02:33 PM

An electronic speedometer calibrator can recalibrate the speedometer but you have to wire it in and it costs more. A replacement speedometer gear just snaps in.

pekoe1111 06-10-2013 06:47 PM

Here i was just thinking about the speedometer, but just realized how it is overstating mileage on the odometer too! Where can I get the gear and instructions to change it? I wonder how long the previous owner had it this way?

RevCo666 06-10-2013 06:49 PM

Here's some info to get ya started:

Jeep Parts, Jeep Accessories & Jeep Soft Tops From The Jeep Parts Experts - Quadratec

Also, Jerry was on the mark for the speedo gear type 42 tooth I believe...

And here's the sticky:

TJDave 06-10-2013 07:38 PM

Depends on what transmission you have also.

My 04 TJ with the 42rle auto read 60 on the speedo and 70 on the GPS. That was with 33" tires and stock 3.73 gears. I never changed my speedo gear, just dealt with it.

Now I am running 35" tires and 4.88 gears. My speedo matches the GPS! Glad I never changed the speedo gear.:)

Jerry Bransford 06-10-2013 07:46 PM


Originally Posted by pekoe1111 (Post 3846410)
Where can I get the gear and instructions to change it?

Here's a very good site with an accurate speedo gear chart (click on it to make it big enough to read) and great instructions on how to do the swap. Changing Your Jeep Speedometer Gear. All you need is a 1/2" wrench. :)

All times are GMT -5. The time now is 01:46 PM.

User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.