heh,... i'm not sure i deserve that kind of credit; they just happen to be local to me.

(i once had my J**p roller-tested there after a tire size change since it's where the local LEOs go; it was surprising to me how while the odo was fairly accurate the speedo was only accurate at one speed; indicated high below that, and low above,... it doesn't seem that making a speedo accurate is a mfr's major concern!)


cheers!
e


On 04/Jun/10 13:02, Rolf wrote:
Someone with more active brain cells than me. I do believe that is the place.

-Rolf

On 06/04/2010 12:56 PM, ernest breakfield wrote:
Rolf,

    would you by any chance be referring to Palo Alto Speedometer?


cheers!
e


On 04/Jun/10 06:08, Rolf wrote:
There is a reputable shop in Cali that adverts in the back of the star IIRC. They specialize in VDO's (they all have the same issue). A few others on the boards have mentioned it as well. Name escapes me. I think its about $150 to have it refurbed, I would go that route with a warranty over replacing it with questionable used parts (says the guy whos gone through 3 85 speedos and is about to just give up on the junkyard and fork over the moola). If you tear the speedo apart the mechanism is, what I would consider to be, fairly laughable. Is a wheel in a cup that spins arounds (either the cup or the wheel is drven cant remember). I consistently found that the odo, if working tends to be correct and the speedo is off (same as your predicament). Right now I have a non working odo and a bouncing but accurate speedo.

Once I get around to getting the VNT installed in my car and doing my own electronic vane control I plan on adding in support for electronic speedos ala w126/201/124 etc. They have their own issues but are easy enough to find.

-Rolf

On 06/03/2010 02:56 PM, andrew strasfogel wrote:
CORRECTION: Should have written "OK - what is the takeaway message from all
that learned discussion?  Am I doomed to forever have an inaccurate
speedometer that reads too high (in mph and miles covered), or is there hope
for an affordable fix?"


On Thu, Jun 3, 2010 at 2:50 PM, andrew strasfogel<astrasfo...@gmail.com>wrote:

OK - what is the takeaway message from all that learned? Am I doomed to foreever have ain inaccurate speedometer that reads too high (in mph and
miles covered), or is there hope?


On Thu, Jun 3, 2010 at 12:57 PM, Dillon, Meade M CIV SPAWARSYSCEN-ATLANTIC,
53310<meade.m.dil...@navy.mil>  wrote:

Sho'enuf, hat tip to Rolf (and Mitch). For a 123.133 the EPC shows that
the speedo and the diff changed for '85, but no changes to the
transmission speedometer gears.

-Max

-----Original Message-----
From: mercedes-boun...@okiebenz.com
[mailto:mercedes-boun...@okiebenz.com] On Behalf Of Rolf
  Sent: Thursday, June 03, 2010 10:51 AM
To: Mercedes Discussion List
Subject: Re: [MBZ] ISO a fix for lousy fuel economy in a W123
turbodiesel - with an incentive

I know for a fact that the speedo is matched to the rear diff and not the transmission alteast in the W123 chassis. Feel free to research it.

-Rolf

On 06/03/2010 10:46 AM, Dillon, Meade M CIV SPAWARSYSCEN-ATLANTIC, 53310
wrote:
I think that the issue is the drive gearing may be the same, but the gear which drives the speedometer (in the tail of the tranny) varies
to match the differential.

The EPC can answer this question...

-Max

-----Original Message-----
From: mercedes-boun...@okiebenz.com
[mailto:mercedes-boun...@okiebenz.com] On Behalf Of Rolf
Sent: Thursday, June 03, 2010 10:38 AM
To: Mercedes Discussion List
Subject: Re: [MBZ] ISO a fix for lousy fuel economy in a W123
turbodiesel - with an incentive

That is pretty much correct. The speedo is based on the rear diff not the trans. The automatics are all the same (for the w123) gearing and all the four speeds end in 1:1 gearing. The manuals differ from year
to year based on engine and reivisions.

-Rolf

On 06/03/2010 10:35 AM, Mitch Haley wrote:

Jim Cathey wrote:


No, I correct myself.  The speedometer is attempting to measure
wheel

RPM, but it's tapped at the tranny tailshaft.  The 85 tranny is
_expecting_ to have a lower tailshaft RPM for a given road speed,
and

so gears up the speedometer tap to make up for it.
You put that tranny in a car with a shorter rear end, and the
tailshaft RPM is higher than expected, and so is the speedometer
output.

I thought the MBZ way was to have the trannies all alike, and match
the speedometer head to the differential gearing.

Mitch.

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