1963 CJ5 speedometer reading low

Warning CJ5 newbie


The speedometer in my CJ5 reads about 8-10 miles lower than my actual speed, any suggestions on how to correct this?

 

Change the height of your tires?

Ideally you could replace the speedometer drive gear in the transfer case, but I recall there's no source for replacement gears.

Most people would just deal with it in their head. If you need a reminder, make a look-up table that converts from indicated to actual and attach it to your dash.

 

They are the tires that were on it when I bought it, that does not mean they are the correct tire size for the speedometer. I do not know what the correct tire size is? A taller tire would make the speedometer report a slower speed I think. I tought there might be a way to adjust the speedometer, perhaps to account for a different tire size.

 

Maybe they are oversize tires that are on it now? That would account for the speedo being inaccurate. The speedo itself does not have any adjustment. That is done by changing the speedo drive and driven gears in the transfer case rear output housing. Different tooth counts will make the speedo read differently.

 

Ahh, ok thanks guys. So if you do have taller tires, the speedo will be inaccurate and you just have to live with. How would I determine the size tire that the speedo is set for?

 

Ok thanks, good info, I guessed as mentioned early, it sounds like something that people just live with.

 

It's also possible the speedo itself is tired, if your ratio is correct. Speedo rebuilders are found in Hemmings Motor News, etc.

I don't get the scientific intricacies of flux induction and so on, but I had a "rotor disc re-burned" (or some such thing) in my '34 Ford speedo 15 years ago, and it has worked perfectly ever since.

 

One other option is a "ratio adapter" that goes in line with the the transfer case and speedo cable. They typically adjust the speedo based upon a percentage of error. I would make sure your speedo is in fact working ok and not gummed up first

 

I just made corrected lines with a sharpie. How did you determine your speedo is inaccurate?

 

I followed my wife down the road at a set speed (30 MPH), and it read about 10 MPH slow. Bigger fish to fry, I will live with it for now.

 

Maybe your wife's speedo is off. Seriously. With oversize tires my YJ reads perfect speed, but the odometer is off 10%.

 

If you have access to a gps unit, that will give you the correct actual speed...
With my 64 I don't have too much worry about "over the speed limit". My speedometer
reads a little faster than I'm actually going....

 

I'm just happy mine works.