Kerry, the torqueflite in its last year w/ the 440 (78) had a lockup converter,
so my guess is that the transmission on my 68 LeBaron is from a 78 440 equipped
car (the 440 is from a 69 NYer except of the intake manifold that seems to be
from a late 70's car, possibly the same car that donated its transmission). In
performance, there is no difference, because at WOT the lockup unlocks anyway.
In fact, the lockup converter may have a bit more slippage (when not locked up)
than the non-lockup in the 68 sedan. The real potential improvement (in
economy) would actually come at low speeds. Say you climb a steep hill at 45
mph and 3rd gear, the lockup car will maintain 1500 rpm just like it would on
level road, while the non-lockup may be 1700-1800 rpm (the slippage is too low
to give torque multiplication, so its just a waist of energy-I have electronic
tachs on both cars). Unfortunately, its hard to record the difference because
A) the black car's odometer under-reads by about 12% B) the black car has a
horrible Rochester carburator and C) the 2 cars have different cams. At higher
speeds though, there is hardly any difference. At constant speed at a true 75
for example, both cars is about 2500 rpm. In fact, I have measured the
slippage of the non-lockup car by raising the rear wheels and revving the
engine on 3rd gear till the speedometer reads 80 (true 75) and the tach still
shows 2450-2500 rpm. This case represents a zero slippage case because there
is virtually no torque transmitted through the coupling (converter) because the
rear wheels are on the air. The slippage in this case would be only 50 rpm or
so. At higher speeds, the slippage even at WOT with this car is hardly
detectible. So, the overdrive effect of the lockup is negligible at highway
speeds. Now, if the converter was a very high stall unit like many modern cars
have, this would be a different story, since these tend to slip a lot more (up
to 500 rpm in the 2500-3000 rpm range). The black car (LeBaron) will keep its
converter locked till about 90 mph (3000 rpm) as long as you are gentle with
the throttle. When it eventually unlocks, the rpm may go up by about 100 rpm
(as I said, this converter seems to slip a bit more than the non-lockup, it may
have a slightly higher stall ratio). However, this transmission may have weak
internal seals since its behavior is not consistent (that would affect the
lockup clutch operation but not the converter slippage once the lockup unlocks).
D^2
Quoting Kerry Pinkerton <pinkertonk@xxxxxxxxx>:
> Splain please about the lockup converter in your 68? I didn't know you
> could put a lockup converter with a torqueflite? How does it compare
> performance and mileage wise to the non lockup car? I'd think it would
> act
> as a slight overdrive.
>
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