[6pack] Q on the Speedo

[Ken Davis]

Thanks Vance --- in answer to your questions

the small lettering indicates 1120 tpm - according to Bob Danielson  it's 
one of the known ones.

Tyre size is 205-70-15's

Speedo is chrome rimmed, but the inner facing surface is black painted, as 
is tach and the other gauges.

final drive s/b standard

Pinion gear?  never touched, tho' the tranny and j-type OD were rebuilt 
about 8-9 years ago

Now, talking with my son.... He says he caibrated the speedo against his 
handheld GPS "many" years ago (but after the rebuild?) and it was reading 
1-2 miles low.

More info -- Orig mileage is unknown (we don't even know if this speedo is 
original).  Within the last month or two, it turned over to 30,000 showing. 
It did not do it by itself.  It would click and click, the odo wheel would 
show a little movement, almost imperceptible, but never click past 29999; 
the trip odo wasn't turning over either.  I removed it and gave it a little 
assist - manually, in turning over.   I could've screwed something up then.

Plus I noticed today while driving with the GPS and marking the glass for 
the 'real' speed points, that the odo was reading well over .1mile faster 
than the GPS (and road markers) showed their version of a mile.  - More 
indication something is a-miss with the unit itself.  I did notice there 
have been PO "repairs" to it -- (i) the needle has broken off sometime and 
been replaced with a painted strip of plastic, (ii) the green light covers 
have been hacked off,

all this makes me wonder if the speedo in the car is the right one...

Its a 73, with a J-type OD unit and apparently the right pinon and final 
drive.  Are there any other members with a 73 with a J-type who can verify 
what the tpm is on their speedos?

Thanks

Ken Davis




---- Original Message ----- 
From: "Navarrette, Vance" <vance.navarrette at intel.com>
To: "Ken Davis" <ken at azkiwis.com>; "6pack" <6pack at autox.team.net>
Sent: Sunday, January 10, 2010 15:25
Subject: RE: [6pack] Q on the Speedo


The turns per mile are printed on the face of the speedo in teensy weensy 
numbers at the bottom of the speedo. It is possible that you have the wrong 
speedo in your car, as there were at least two different speedos on the 
later (chrome rimmed) speedos as I recall.
I do not know about the earlier black rimmed speedos, if there was only one 
calibration or if there were more.

Possible sources of error: Wrong speedo as mentioned above. Wrong speedo 
pinion gear (in tranny at the end of the cable). Wrong size tires (205-70 
should be ok). Wrong final drive ratio (unlikely), speedo miscalibrated.

Vance

      Vance Navarrette
    Cogito Ergo Zoom
    I think, therefore I go fast