Several things have to be written in the proper order here. Hopefully I can do that.
All the CUCV's with the NP208 tcase had the same speedometer gears inside when they left the factory. The M1009 being the odd geared truck, got the cable reduction box added on externally. The reduction box is designed to speed up the speedometer cable.
A stock 31 inch tall tired M1009 with 3.08 gears turns just a little over 2000 rpm at 60 mph. However, 2000 rpm with 31 inch tall tires and a 4.56 gear ratio is 40 mph. Removing the speedometer reduction box makes the speedometer indicate 40 when you are really going 60. That is why the box is there. No other parts need to get changed and the supply line is smaller for the military.
That should answer what you should be indicating if everything else is correct.
Then there is the 25 year old truck that has been beat and abused factor. If the speedometer is jumping around, mostly faster than it should be and not making noise. Then you need to remove it, clean it and oil it. Especially the little flywheel looking thing on the back. 3 in 1 oil, air tool oil or anything light such as those will work. Use a drill to turn it and see if it is better. Mine starter out indicating 85 at 60 actually and jumping around. I hooked a drill up to it and the drill indicated 50 on low. Cleaned and oil, the speedo only indicated 35 on low drill speed. It was dead on back in the truck too. For about 1500 miles, now it is starting to bounce around again, but still settles down to accurate speeds after a few miles.
If the speedo is bouncing around and making noises. Then you need to look at your cable. Pull the cable out of the case, look for burrs or snags, lube it and put it back in. Problem should be gone.
these trucks are before the sensors I will look in the morning at mine its a 1028 but same speedo gears and tell you what color gears and maybe numbers on gears are in mine! do the 1009's use the 208 transfer?
