converters/ fluid couplings

[dardal@xxxxxxxxxxxxxxx]

> 
> I don't have any experience with any Imperial as 'new-fangled' as a 60s
> or
> 70s model.  :)
> 
> Most highway cruising, though, is at way less than 4000 rpm, so
> presumably
> slippage becomes a factor for them, too.

Yes and no.  As said, at 75 mph crusing w/ the typical 2.94 gear ratio most 
Imperials have, you have about 2500 rpm.  So, yes, the engine speed is less 
than 4000 but you are not WOT when cruising.  Unless you hit a steep hill or 
try WOT at the lower revs, slippage is not a serious factor (that is for a 60-
70's Imperial).

In fact, during the 60's when these transmissions were built, the potential of 
a lockup converters was well known in the industry.  However, everybody 
realized that the improvement that such a device would offer did not worth its 
cost (because the converter slippage is very low most of the time).  In modern 
times, the engines lost torque and the requirements in performance increased, 
so they started installing high stall converters.  Also, overdrive 
transmissions became common.  Overdrives tend to load the engine at low speeds 
where slippage is high.  Now, the potential benefits of the lockup are higher, 
so they are used on virtually all modern cars.

Now, why did the 440s in 78 had lockup transmissions?  Oil crisis may be?  As 
said, I cannot verify any mileage advantage of my lockup equipped LeBaron.

D^2, 2x68s