By Allen L Phillips
The automatic transmission came into general use in the late 1940’s and in the late 1950’s racing enthusiasts began modifying the 4 speed GM Hydramatic transmission for drag racing. There have been substantial advances from the early 2 speed transmissions like the Chevrolet Powerglide to the highly efficient six and nine speed transmissions found in newer cars today.
Another recent development is the Continuously Variable Transmission (CVT) which, as the name implies, does not shift but provides continuous torque to the wheels. These transmissions remind me somewhat of the Chevrolet Turboglide transmission which showed up briefly in the 1950’s and, while very smooth because it didn’t shift, was horribly inefficient and had a failure rate that led to their quick disappearance. Most of today’s CVT transmissions have overcome those problems, are very reliable and, as used in the Toyota Prius that I drive, contributes to 56 miles per gallon.
With all of the technical improvements in transmissions, one thing that hasn’t changed is the need to maintain transmission fluid. With trouble free operation and car salesmen who sometimes soft peddle the need for it, maintenance of transmission fluid can become a low priority. Additionally, manufacturers have changed transmission configurations so that is more difficult to service them, driving up the cost.
There are two kinds of service: the first on transmissions that have an internal filter that needs to be replaced which requires removal of the transmission pan; and the second that has no serviceable filter and only requires draining the fluid and refilling with fresh. Our shop refers to the first as a transmission “service” and the second as a “drain and fill”.
In either case, some contaminated fluid will remain in the transmission after the procedure, diluting the fresh fluid that we put in. This is why the transmission needs to maintained regularly in order to stabilize the integrity of the fluid over time to help guard against failure.
Another consideration is that the design of many newer cars prevents routine checking of the level or condition of transmission fluid during an oil service. So we frequently can’t warn you if the transmission fluid looks dark or smells burnt like we can on earlier models.
So, while we generally check your service history every time you visit, it won’t hurt to ask next time in, to be sure your transmission maintenance is up to date.