It is very annoying that our Challengers do not have transmission dip sticks to check the fluid level. If you want to do this yourself, you can buy a Dorman dipstick (Part #917-327) for about $20, on Amazon, or the Miller tool equivalent (Part #9336A). This, however, is not a permanent dipstick for your car. It is a measuring tool to check your transmission fluid levels. You will note that your transmission fill tube has a cap that reads, "For Dealer Use Only." Simply place a rag over the cap and gently grab it with channel locks to twist it out. Then after your engine warms up to 185 degrees, cycle your transmission through P - R - N - D just to make sure the fluid has circulated. Then add fluid, if necessary, to the targeted mid-range. After you complete this process, screw the threaded OEM transmission fill tube cap back on.