Quote:
Originally Posted by JB3
Overheating automatics on grades is not that unusual, I've done that a few times on a bunch of different products where you can smell it when the transmission is constantly shifting. Really what does it is all the shifting and hunting building major heat, especially if the speed you are going on the grade is right between a couple gear ranges, so the transmission is constantly hunting, too low in one, too high in another, with the operator alternately flooring it and backing off as the hunting continues, perpetuating the hunting.
Better to manually pick a gear and stay in it, cools right down up or down grade
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The constant shifting of the automatic is quite typical when it cannot hold the higher gear on the grade, but accelerates in the lower gear. This behavior only affects the durability of the clutches and has no relationship or effect on the development of heat within the unit.
The unit develops excessive heat by definition simply because the torque converter is undergoing a significant amount of slip. The speed of the input shaft is probably 300-400 rpm higher than the output shaft and that difference is churning the fluid into heat. The temperature of the fluid is going to climb significantly and its life is going to be commensurably shortened.
Not much you can do about this unless the vehicle will go into lockup in the lower gears. Surprisingly, the POS Dodge B-250 locks up at 29mph in third, much to my general dissatisfaction around town. If, however, you are willing to climb the hill at a lower speed, and use lower gears, the torque required is significantly less, the slip is therefore less, and the heat generated is less.
If it does lockup, the massive heat buildup is eliminated. However, the torque multiplication is also eliminated, leading to a general dissatisfaction by the driver.
06-03-2013, 10:08 AM
1987 560SL
Linear Mode
