Racing a TR3 A Type Overdrive
Please see what you can find in the archives.
For many years the TR3 was one of a very few cars not allowed alternate
gearbox ratios in SCCA E Production. Using second gear overdrive was
essential with a full race motor to bridge the gap between 2nd and 3rd. I
spent
thousands of hours studying and modifying the OD. Running a pressure gauge
during events is necessary, as is not allowing it to leak on the driver. The
gauge will show when the solenoid is out of adjustment, and most critically,
when there is a running pressure drop. If the accumulator piston does not
reach the blow off holes, that oil no longer gets to several parts. The
specks for the accumulator bore are very tight, and honing to remove the steel
piston ring scratches will only work a few times. The TR4A IRS/TR6 piston,
sleeve, and spring provide a much lower volume and pressure, but a
replaceable sleeve is a good idea. Much research about piston displacement and
pressure pointed me towards a Jaguar sedan assembly that was NLS, but JRT,
with the help of a UK Jaguar club, provided a few sets of piston and sleeves,
and I also located the matching springs. I did find it necessary to run an
oil cooling system with an electric pump and MGC auto gearbox cooler, all
set low enough that it would not flow back into the gearbox during the early
laps before the pump was turned on. Keep in mind that I was running slicks
and often ran where the track temps were high.
TR Regards, Hardy
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