John :
It's very common for the speedo and tach to read higher as they age, I'd
check out the calibration of the odometer first (as it does not vary with
age). If the odo is accurate, then the problem is inside the speedo head.
If the odo is also 6% high, then your problem is gearing/tires.
> I believe the TR4's were made with different rear ends (4.1:1 or 3.7:1),
> which I also belive was based on whether the car had overdrive or
> not (4.1:
> for O/D cars?).
The 4.11 gears were normally only available with OD, but most overdrive cars
had 3.70 gears. However, note that a 4.11 speedo will read low when used
with 3.70 gears, not high as yours does.
> Does this mean that different speedos were used (i.e.
> different gears inside), or was the transmission speedo gear changed?
Until sometime mid-TR6 production, the speedo heads were changed. There is
a calibration number on the face for the number of (cable) turns per mile
the head expects.
Check out Tony Rhodes' excellent article on the subject at
http://ourworld.compuserve.com/homepages/arhodes/
> 4. Is there anything else, short of changing tires, that I can do?
Speedometer shops can make up adapter boxes for any combination of tires and
rear axle ratio.
Randall
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