speedometer

[mack88]

my 1987 Mack speedometer is acting up gets stuck right over then it work its self back and is jumpy i no cable is new was wondering if its the head or would it be down by transmission.

Edited March 9, 2019 by mack88

[41chevy]

I would look at the drive on the trans, check check gear for grit or damage and look at the hex in it. That is the easiest place to start. I have seem them wear enough so still work but slip. If that checks out than go to the speedo head itself.

Edited March 9, 2019 by 41chevy

[Rob]

if the needle is deflecting and sticking the problem is in the indicator itself. Probably old grease which has lost it's lubricity qualities, (hard, dry). Not hard to repair but a simple and quick repair is to remove the instrument, submerge in hot water, allow it to heat soak and swish it around quite violently to soften and desolve and dirt/grit internal. This will also loosen/soften the old lubricant, (at times). Follow this up with a double rinse of warm distilled water or a mixture of "Calgon" and tap water to eliminate water spots. Allow to dry or bake in the oven for about 30 minutes at 250 degrees to force dry.

[mack88]

Thanks guys.I'll check both.