Speedometer

Put a D20 t-case in my 51 CJ3A build and when I hooked up the speedometer cable it runs backward. Does the speedometer drive need to be swapped out. If so what replacement is correct. It is also a new speedometer could the problem be there? The t-case is turning clockwise but the speedo needs to turn counter clockwise.

 

D-18 and D-20 turn the same direction for the speedo. If you look at the cable core at the D-20 it will be spinning clockwise but the other end where it screws to the speedo will be CCW. I don't see your problem..

 

When bench testing the new speedo head it works fine. Put it in the Jeep and the odometer goes backwards and the speed does not register even though the cable is turning the right way. Dug up an old speedo head and installed it and it worked. I am confused. I bought the speedo off ebay and I didn't notice that it was coming from India. Still doesn't explain why it works on the bench and not installed.

 

That is strange.....I swapped my d-20 for a d-18 and my speedo hooked right up and worked great with no mods. I'm interested to see what you find out. Is it possible your only looking at it when you are going backwards?

 

Gotta be the gremlin. Sure you are spinning it the right way on the bench? Seems unlikely that it would change just by being installed. Plus I didn't think odometers would spin backwards.

 

The odometer part is gear driven and it doesn't care cc or ccw. If the speedometer didn't have the stop pin it also would read backwards. Spin the old speedo with your fingers in the direction that makes the needle jump then spin the new one the same direction. What did you find?

 

Figured it out. The new speedo must be geared high. Jacked up the back of the Jeep and in 3rd gear at higher rpms it went to 10mph. The old one read 40 at the same rpm. Not sure why the odometer was going backward it doesn't now. Maybe I imagined it?

 

if that is so why dont the miles go away in reverse?

 

The older odometers would run backwards that is why used car dealers would put a drill and run the mileage back. The feds made the manufactures put a reversing lock on them to stop this but I don't remember the time frame this started. To answer your question sterlclan, I don't think you would notice in just a few hundred feet of backing up. I have a few speedometer heads so I will put a drill on one and see for sure if these jeep one's will indeed back up.

 

Just tested 3 early cj5 speedometers and they all rolled backwards on the odometer.

 

well walt i stand corrected... ferris' buddy cameron didnt wait long enough i guess....

 

Well that is the purpose of this forum and we live and learn. This forum is a mountain of info and knowledge from all members. Not all is jeep related which makes it so informative and interesting. The best part is that the members here freely give there time, advice, knowledge, and sometimes even parts, so it is a win win place to be.

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