VDO Odometer fix.......and tach. question

[Gfbourcier@aol.com]

Hello all,

I have the VDO gauge set in my 87 4000 and have seen similar spedometers in 
may of the 4000/5000 models. I believe the spedometer to be model W1580 (at 
least that is the number below "unleaded fuel only.")  Have you ever had the 
spedometer function with no problems, but a non-functioning odometer?  
Finding myself in this situation, I took the dash apart and removed the spedo 
head.  On the left side of the housing, you can see a small yellow gear that 
is turned by a small white worm gear.  If the yellow gear slips off of the 
worm gear (as it does pretty easily - bad design, I guess,)  the odometer 
stops working.  To fix, locate a small cotter pin or similarly "sprung" metal 
or plastic piece (I used a paper clip, but had to bend it a touch to suit my 
purposes.)  Place the clip over the pale white housing in line with the 
yellow gear and leave 1/4 inch (or 6-7 mm) extending past the housing, 
glueing in place.  Now the yellow gear doesn't have enough space to jump off 
of the worm gear.  

The odd problem that I need help with now is that the tachometer seems to 
read 700-800 rpm low.  What I mean is that at normal idle, it reads zero (the 
needle at rest with the engine off is WAY below zero.)  Rate of change is 
fine, no pinched wires in the dash, just a low reading.  Are these things 
adjustable?  There is a black knob at the base of the tach, similar to the 
trip reset knob on the odo.  My car has the trip computer, although it is not 
functioning, nor has it since I bought the car.  Are the two related.  Thanks 
in advance for the help.  I have absorbed a lot of info from you all over the 
last month or so.

Gil Bourcier
87 4kcsq - Columbia, MD USA