Replacement speedometer and speedometer drive gear question.

[llong66]

Hello,

I needed to replace the inst. cluster on my 85 M1008 and while mine worked fine, I kept the speedometer that came with the new cluster
because it has less miles on it and in Indiana, on a truck of this age, the milage listed on the title is simply exempt.
I noticed on my first drive, that the tranny was not shifting at the speed it had before the replacement and verifyied with my GPS
the new unit is off by 9-10 mph.
My question is, is the unit used in a M1009 itself, different than on an M1008? I had always thought that this was set at the tranny with the speedo drive.
I noticed this change BEFORE I bought the new tires I have also posted about and other than tread ware, the tires are the same size

Thanks much!
Greg

 

[scottladdy]

The -20P shows a single part number for the speedometer, no UOC's listed:

3 PAOZZ 11862 25052373 SPEEDOMETER 1

Speedo gear is definitely different due to the different final gear ratio. 4.56 vs 3.08

I have found that the bearings in the speedo head can get gummed up with time. I carefully place a drop of synthetic oil on each bearing and things go back to normal. YMMV.