Long gone are the days of transmission dipsticks in the engine bay. On most newer vehicles you can’t simply open the hood and check the level or condition of the fluid. Why would the manufacturer remove the driver’s ability to access and check the fluid level? We have asked that question of several engineers, and the answer is the manufacturer wants qualified technicians working on these vehicles, i.e., dealership technicians.
Why is the fluid being guarded so closely now? In the old days, if you got aggressive filling the transmission and put a little extra fluid in, it would likely puke out of the vent and not much more. So, if you happened to add ½ qt. too much, there was not much concern. Now we have units like 6T40, 6T70, and other transmissions that will overheat if overfilled by that same 1/2 qt. It is because of the damage that comes from under or overfilling the transmission and using the wrong fluid type, that the manufacturers have restricted access. Over the last 20 years, fluid type and level have become more and more important. In later articles, we will discuss clutch learn and adaptive strategy and you will see the importance of correct fluid level as it relates to drivability. With that being said, it is very important to set the fluid level correctly. For this article, we will focus on the different styles of fill procedures and how to access them. With many different transmission types available there are almost as many ways to correctly fill the transmission.
For the reasons above, many manufacturers have ditched the stick in place of a level check plug, or a short stick that is accessed from under the vehicle to be used by professional automotive technicians.
I believe it comes down to money like everything else. This process keeps the customer coming back to the service and parts department to spend money. The perfect example is DaimlerChrysler’s service tool (see photo below) to check the fluid level. It could be purchased from the dealer parts counter for about $50. Now, if they wanted only professionals working on their transmission, they would have restricted the sale of this tool to professionals only, however, they made it available to anyone. Hmmm???
I’ll try to explain as many fill procedures as possible, but this article would go on forever, if I covered everything in exact detail. You should consult the service manual on your specific application.
Before we get into the different fill processes please remember: