More than likely the squeal is from the speedometer. They are very easy to fix. In your case pull it from the truck and turn it so the cable fitting is up. Put a couple of drops of engine oil, I have been using Mobil 1 with 100% success.
Occasionally you need to disassemble the instrument and lube some of the other shafts in them but the squeal is the input bearing.
The Mitsubishi Speedometer is not made to be rebuilt in any way.
You can dissassemble the upper frame frome the lower frame but there is NOTHING to lubricate in the upper frame. In fact lucbricating it would be adding grease to something that is NEVER greased.
there is also no such thing as an " input bearing " in a speedometer.
The noise you hear is a dry speedometer turning against a small thrust washer. eventually it will "catch " the washer and self destruct the speedometer.
I am giving you this info not to be a jerk but just to inform you.
The speedometer is made up of a lower main frame ( magnet and frame in brass bushing ) and upper frame ( pointer , faceplate , speed cup and odometer assembly) .
The cable rotates a magnet in a brass bushing in the lower frame. The magnet produces a magnetic field wich makes the speedometer go up. a small hairsping brings it back to zero.
The lower frame is pressed together. a lot of Foreign speedometers are designed this way. The metal is so rigid that when it is pressed apart, the metal cracks and breaks off. That is why the average Japanese Speedometer can not be rebuilt.
There is nothing the matter with adding a couple drops of oil ( i prefer clock oil ) to the lower frame to quiet it down. I would get a drill to run the unit upside down and add some clock oil to the input as it is turning.
Warning!---too much oil will infect your speed cup. you will know when this happens as the speedometer will read 80 when you do 20 mph.
I really should get a spare mitsubishi speedometer and take it apart and post pictures so the peeps can really understand as well as see what i am saying.
