"Does anyone know if it's possible to adujust the calibration of the
speedomter? If so, how?"
Only way that I know of is to change the tire sizes, which is the most
common way they wind up off in the first place. There is a calculator
available on the internet that I've used where you can put in the
original tire size, then put in another tire size and it will give you
speedometer error. You can find the calc by searching.
I'd also do a measured mile timing to verify the speedo is off.
Unless you're running huge tires on that SD I would suggest there is
something other than the speedo that's out of whack, maybe the cop.
Here's your calculator:
On Fri, 01 Apr 2005 07:01:24 -0800, dougmcp wrote:
There are a couple of possibilities. Given the vintage of your
car, it's possible that there has been an incorrect replacement
of one part or another, throwing off the overall speedometer drive
ratios. This one is dead simple to check. Find a highway. Note your
odometer reading. Drive about 20 miles, watching the mile markers.
Watch the odometer to see if it's clicking over about the same time
after each mile marker. And, oh yeah - do watch the road. If your're
odometer is turning over nicely at the same point from each mile marker,
then the drive ratio's are correct. (Note: this is for the mechanical
speedos - you know, the one's with a spinning drive cable and geers -
the newest electronic units "drive ratio" is done by a counter in a
chip - which in some cases, can also be "adjusted")
If your odometer is NOT kicking over at the same point after each
mile marker, your overall ratio is off. Take note of how far off it
is after 20 miles - the speedo shop may want this info.
In either case, any good speedo shop should be able to help. There
are a variety of reasons a speedo can be reading wrong, depending
much on the design of the speedo and whether it's the older
mechanical rotating magnet design or one of the slightly newer
electronic coil designs, or the latest digital designs.
http://www.nhspeedometer.com has been in business longer than
a lot of us. I won't claim that they have bargain basement
prices, but I've used them twice and they did what they were
supposed to do.
I believe W126 speedometer 'counts' pulses to determine distance and
speed. In another word, there is no steel cable connecting transmission
to speedometer. It is just a wire. There is nothing inside the
speedometer to adjust.
Is the cluster original? Different engine/tranny configurations use
different parameters to determine a 'mile'. Clusters are not
inter-changable between different configurations, even if they all come
Paul Valois wrote:
It may count pulses for speed... but for odometer, there are three different
3rd gear for different cars. I once put in a 500SEL speedo into my 380SE and
it is too fast by 5 MPH all the way... same for odometer... too fast too.
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