IML: overdrive torqueflite and stall speed

[David Whitney <hazegreen66@xxxxxxxxx>]

If you have a tall rear gear such as the '80s Imperials or a ratio below 3 for older cars, you must be aware of the impact of overdrive on your RPM and relate it to the transmission's stall speed.  If you cruise at 2000 RPM on the freeway in direct drive, then add an overdrive gear that decreases RPM by one-third, suddenly you are cruising at 1334 RPM.  That is so low your transmission may still be slipping even though you are on the freeway.  Slipping creates heat and decreases mileage.

 

The above demonstrates the main reason for having a lock-up torque converter.  Locking up eliminates the slip and associated heat and, as was previously mentioned, increases gas mileage by approximately 10 percent.

 

If you have normal freeway rear gears, you must must must use the lock-up converter with any overdrive unit, including GearVendors.  Anything from 3.23 and shorter and you can decide for yourself whether to use the lock-up.

Happy motoring,

David

'91 K-Imperial driver
'66 LeBaron dual air and every option known to man

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