At 03:30 PM 1/28/02 -0600, you wrote:
When you load the torque converter at these low
>speeds climbing a hill, a lot of slippage will result which is nothing but
>direct loss of energy converted to transmission heat.
****** This is very true....
That's where you need the lockup converter.
****** This is very NOT true... Dim, your infactuation with using a lock-
up converter is good only in theory.. The converter is NOT the
only source of slippage.. And the less conveerter slippage the more
clutch slippage, creating the most heat and excessive wear... Your
use of a 2.0 gear,going into O/D, and locking the converter, would
w/o any doubt create a mega increase of plate slippage/wear.. Because
you are good with theory I am going to direct you to look at a FSM..
The one for your '68s is a good start.. If memory is correct section
21 is transmissions... Pay close attention to flow diagrams and given
flow pressures... If you were to somehow be able to install a lock-
up into your '68 trans you would probably burn it reasonably fast. The
later transmission that did use lock-up were made to accept.. Part of
the accepting were changing release spring pressure and plate spec.
The statement about higher engine load resulting in poorer fuel economy
needs to be a bit more explained. Typically, spark ignition engines are
more efficient at higher loads, for two reasons, the most important of the
two is that as the throttle opens, the intake restriction diminishes, so
the "pumping" losses drop. However, if the load of the engine is increased
to the point where the mixture starts getting rich, then you might start
loosing MPG.
******* Your theory is correct.. The practicals are not.. Remember what is
regulating fuel flow.. As vaccumn drops, rods or power valve opens
allowing for INCREASE of fuel.. This need not to happen at, or near
WOT...
> This however happens fairly close to WOT, so it will have to be a very
steep
>hill, in which case you have the option to down shift to direct.. The
>super low gear ratios like the 2.15 usually give better MPG's on the
>highway but at the loss of low speed performance and economy. If I paid
>the $ for an overdrive, I 'd rather use it for performance, but one could
>rather choose to maintain a relatively high ratio and use it for
>economy. If in the US though, it might take many years to pay back through
>fuel savings.
****** I view it as a performance modification.. But one that adds
drivability.
I can now use a 4.10 or a 3.91, and an O/D, and still have my desired
level of performance but with decreasing final drive I have now made
an increase of drivability..
I guess the most notable example of how this all works would be to look
at a four wheel vechile..Except opposite.. Look at LOW RANGE as your
normal ratios and then HIGH RANGE as over drive.. As we all know, in
low range we can pull like gang busters.. In high range, we have
reduced RPM,, hence fuel usage<to a point>,motor wear,motor noise,etc.
****** The statement of saving.. This is subjective.. I orginally got
involved to see if I could convert a muscle car into one that made
decent mileage.. Where I did suceede to an extent.. Where I excelled
was less RPM use, resulting in an increase of motor life..Hence more
time between rebuilds..
**** How would all this relate to our Imperials.. Weell,, as anything one
would need to look at priorities.. In my case, I want the higher
ratio <3.55/3.91> and still maintain drivability... Would the use
of an O/D unit in 90% of the members on this list be benificial..
Resounding, NO... The cost would outway any advantage... To the
few who use their Imppys for more than local crusing, where they tow
their boat or car trailer and still wish to drive to the Calif event
listed today, a definate YES.. To try and make use of a 518. I would
not even consider such... 727 is stronger and the use of a Gear Vendors
unit is too simple.. Plus stronger and better warrentee....
Sorry to be soooo long winder ehre, peeps.. I tryed to keep
it reasonably short...
Robb
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