From: William Huff <whuff@xxxx>
To: Chrysler300@xxxxxxxxxxxxxxx
CC: classiccars64@xxxx
Subject: [Chrysler300] torqueflite trans.
Date: Wed, 04 Jun 2003 00:18:10 -0500
Even though the transmission may not automatically downshift into second as
a passing gear, if you are still within the torque and HP range of your
engine, it is usually possible to manually downshift. At 60-70 MPH I would
think that at full throttle you could still down shift without over revving
the engine. I would use full throttle to avoid a severe jolt from the
mismatch in engine and transmission output speed. I threw together some
real rough and ready figures using a lot of assumptions to see what might
have happened if the tranny did downshift or if you manually did so.
I know post '62 727 aluminum torqueflites use a final drive ratio of
1.00:1 and a second gear ratio of 1.45:1. I can't find the gear ratios for
the cast iron torqueflite, but the second gear is probably very close to
that of the later tranny. If we assume two different tires for a
comparison, 235R75 x 15 and 225R70 x 15 we find the 235-75 series has a
diameter of about 28.9" and the 225-70 series a diameter of about 27.4".
Assuming a rear end ration of 3.23:1, at 70 MPH and in third gear, the
engine would be turning 2638 RPM with the 235 tires and 2773 RPM with the
225 tires.
A downshift to second at 70 MPH with a 1.45 second gear ratio would lead to
3825 RPM with the 235 tires and 4020 RPM with the 225 tires. I believe the
standard 413 in the "F" developed 375 HP at 5000 RPM and the higher
performance engine developed 400 HP at 5,200 RPM. It appears to me as
though the engine would not be over revving.
Since maximum torque develops at 2800 for the 375 HP engine and at 3600 RPM
for the 400 HP engine, looks like you were sort of caught right in the
middle, beyond the torque band and not really in the HP range for the
standard 375 HP engine. I sort of feel that if you have the 400 HP
engine, it must have been an unusually fast car to pass on by like that.
Next time, slip it into second right when you think something exciting
might develop and be sure to start accelerating earlier. You have to have
a MUCH faster car to overcome the momentum gathered by a long head
start. It is easy for another car to be going 20 MPH or more faster than
you when they come even, if you wait till they are almost there to
accelerate,...well, you know.
If you do want to manually bring the engine to it's peak, I recommend an
accurate tachometer, new valve springs are quite helpful as well.
That's my Monday morning quarterback take on the situation from a few
thousand miles away.
Regards,
Bill Huff
I believe it depends on how the transmission is set up which in turn
depends
on your motor's torque curve & rpm capability and your axle ratio. If you
have a stock 413 with a 3.23? rear gear, then you wouldn't want it to
downshift over 70 mph or you are likely to over rev the motor.
Steve Galezowski
----- Original Message -----
From: "thomas powers" <classiccars64@xxxx>
To: <chrysler300@xxxxxxxxxxxxxxx>
Sent: Tuesday, June 03, 2003 9:07 PM
Subject: [Chrysler300] torqueflite trans.
>
> Hello.
> I have a question what speeds can a torqueflite transmission
downshift
> cause i was going 60 or 70 m.p.h. in my 60 300F and a car tried to
pass
me
> when he was way back to start with then i hit the gas and it would not
> downshift so i could get ahead and the car eventually got right by me
and
> passed me.But it would not have happened if the transmission would have
went
> into passing gear whats wrong thank you tom.
>
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