It could be your speedometer head. Try this: remove the connection from your transmission and connect the cable end to a cordless drill. Then spin it...very slowly at first. See if it rises to around 60 or 70 steadily as you increase the drill's speed and then smoothly drops when you reduce speed. If it does that, it is not likely you have a problem in the head. If on the other hand it rises sluggishly and then seems to reach a point where it doesn't rise much anymore, you might want to remove the speedometer and do some checking. On the back (where the cable attaches) you'll have a 2 part brass affair. Please see image one below. If you move this between your thumb and forefinger you should see movement of the needle rather quickly and this end piece should spin very easily. If you flick it like you're snapping your fingers, the needle should jump to around 30 mph quickly and then drop back down. If this feels sluggish, remove the brass plug (second image), add a light oil (like 3 in 1 or sewing machine oil) and work it until it loosens. You can also lubricate where the 2 part brass piece is split by a thin washer. This all needs to be very smooth. There is also another place where you can lubricate...this controls your odometer shaft, but it usually is okay. In the final image you can see the other oil location. Please ignore the red arrow. That image was used when we were repairing a broken needle shaft here a couple of years ago.
Last edited by Jon G; 04/25/20249:23 PM.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
