At 05:34 PM 10/31/00 -0500, you wrote:
> Yep, I've thought about the GV overdrive. Pricey though! :-( As
> far as lock-up vs non lock-up goes, what are the pros and cons there?
> -Jon-
Jon
I came across this on a site. Hope it helps.
Lockup converters contain another part: a torque converter clutch.
When the clutch engages, it allows the converter to lock the engine
to the transmission input shaft, providing a direct 1:1 communication
from the motor to the transmission.
Why is this necessary, or even desirable? In many ways, it comes down
to fuel economy. Lockup torque converters have become popular since
automakers have been stuck in a sort of Catch-22: Car buyers
overwhelmingly prefer automatic transmissions, but automatic transmissions
are not as fuel efficient as manual transmissions and automakers must meet
government-mandated corporate average fuel economy targets. Overdrive
transmissions have been one step along the path toward increased fuel economy
from an automatic transmission. Overdrive transmissions allow the
motor to spin at a lower rpm during cruising speeds. A higher final
drive ratio (numerically lower) does the same thing.
However, when the engine spins more slowly, it creates more slippage within
the torque converter, and more slippage creates more heat. Heat within the
torque converter reduces fuel economy and can harm both the torque converter
and the transmission. The solution is to allow the converter to lock up at
a 1:1 ratio. Lockup eliminates the slippage, which reduces heat and improves
fuel economy.
Usually, lockup converters are used in stock applications, but not in
higher-performance vehicles. However, some drag racers choose to run
lockup torque converters, too. It is possible to lock up the converter
at wide-open throttle manually (by using a switch) or automatically
(via a racing computer chip). It has been estimated that locking up
the converter at WOT in a relatively stock doorslammer, such as a Buick Grand
National, can pick up about a tenth in quarter-mile ETs; however, it also
speeds up wear and tear on the torque converter clutch.
I personally think that most drag racers prefer a non-lockup converter
because of the loss of the converter's torque multiplication factor when
lockup occurs (I could be wrong here). Most aftermarket converters have
a 2:1 torque multiplication factor.
Bob
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