Subject: [Fot] Racing a TR3 A Type Overdrive

From: [email-masked]
Date: Mon, 12 Nov 2012 19:28:56 -0500 (EST)

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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From: "MadMarx" <[email-masked]>
Date: Tue, 13 Nov 2012 18:26:55 +0100

The only issue I have with a J-OD that it switched off during the race.
The OD always went out and popped in a very short manner.
No idea what this could cause.
- New solenoid (it happened with the old solenoid too)
- wiring is connected well
- oil level little higher than normal

Cheers
Chris

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Von: [email-masked] [mailto:[email-masked]] Im
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Gesendet: Dienstag, 13. November 2012 01:29
An: [email-masked]
Cc: [email-masked]
Betreff: [Fot] Racing a TR3 A Type Overdrive

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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From: Randall <[email-masked]>
Date: Tue, 13 Nov 2012 12:58:40 -0500

> The OD always went out and popped in a very short manner.

FWIW, when I had that problem, it turned out to be the little ground wire for the solenoid.  The quick connect was trapped on the tab, would not pull off easily, but was very slightly loose.  Vibration, heat and the ever-present oil film would let it open up for just a fraction of a second, then connect again.  

Replacing the quick connect and cleaning up the brown corrosion on the tab solved the problem.

I have also had a lockout switch that would do the same thing.  Removing the shim washer got it working again.  But I doubt you have those on your race car.

Randall

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From: steve <[email-masked]>
Date: Tue, 13 Nov 2012 13:21:41 -0500 (EST)

Hardy, I found your detailed OD info very illuminating.  No, I don't even run an OD unit in my TR3 but I enjoyed your write-up nonetheless.  I can see that you've put a huge amount of time and effort into pushing your machine to it's uppermost limits of power and reliability.  Very cool!

~Steve

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>Subject: [Fot] Racing a TR3 A Type Overdrive
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