Guages not working

[cj7jeep81]

The speedometer and gas guages do not work in my truck ('78). I have already replaced the speedometer cable, and that didn't help any. The needle never moves, and neither does the odometer. Could the gear in the transfer case need to be replaced? If so, how difficult is this?
The gas guage reads all the way to the right (past full), until I get pretty low on gas. Then the needle bounces around. Would this be bad wiring, bad sending unit, or something else?

Thanks in advance!!

 

[Muddytazz]

One thing to try (it worked on my 75) is i took the dash apart and tightened up the mounting nuts on the backside of the gauges. Worked great and is still working /forums/images/graemlins/thumb.gif hope this helps.

 

[cj7jeep81]

I will give that a shot. Any other ideas?

 

[fredekr]

No experience with the gas gauge but I've been working on my speedo recently. First off, locate the problem: if you disconnect the cable from the transfer case end and spin the male prong, does the speedo move? You should be able to do it with your fingers but you can also clamp it in a drill chuck if in doubt (counter-clockwise will read on the speedo). If that doesn't work, then you know your got problems somewhere between the xfer case and the speedo (course, you might still have xfer case probs, but one thing at a time.) Is your cable straight through, no cruise control?

Anyway, if your problem is at the xfer case, like mine is, the following thread will provide some insight:
speedo L transducer

My truck was missing this. I tried plugging my cable directly into the xfer case, but it socket there is round -- either rounded out or needs some adapter key, like the L adaptor mentioned above -- so the square speedo cable prong doesn't "catch" on anything. However, I got it to work by taking a thin strip of aluminum (aka beer can /forums/images/graemlins/rotfl.gif) and shimming the round socket so that the square prong is snug.

The only problem is that the purpose of the adaptor is to change the ratio to accomodate for gear or tire size. My speedo is 15% off at the moment, but it's better than nothing. /forums/images/graemlins/thumb.gif

cheers!
Kevin