I have a lot of content that I’ve recorded that I need to share. Today I’m posting information on the work I did on the 2005 E320 CDI’s (W211) transmission (NAG1, aka 722.626). The performance increases that will be coming demand a solid foundation. It would be a recipe for failure to increase performance without handling basic maintenance tasks first.

Things I learned in my multiple transmission sessions will be useful to others, too. I often learn things the hard way, so that you don’t have to! The process I show in the video for changing the transmission fluid and filter aren’t terribly unusual, except for a few things:

The Dipstick. The transmission in these cars has a dipstick tube, but no dipstick. The tube has a locking cap with a red tab that gets broken when removed. So, I wound up buying dipstick with a number of red tabs and o-rings on Amazon. The dipstick isn’t customized to the length of the dipstick tube, so I’ll keep it in my Mercedes tools. Here’s where I got mine. I’m not a huge fan of Amazon, but they had the part at a good price and deliver products very quickly: https://www.amazon.com/gp/product/B075PQFDJ6

The Cannon Plug. These are bathed in automatic transmission fluid and will often leak. When they do, the ATF can wick its way up the wiring harness into the transmission control unit and cause some very expensive problems for you. I recommend changing this when the transmission is drained and the pan is still off. https://www.idparts.com/pin-transmission-adapter-plug-ring-7226nag1-2035400253-68021352aa-p-4632.html

No Torque Convertor Plug. My other Mercedes vehicles have had plugs in the convertors, allowing much more of the ATF to be drained from the transmission. Because of this, and the fact that common workarounds to flush the fluid are hazardous to the transmission’s health, I simply wound up changing the fluid that can easily be drained several times. The best deal I could find on the appropriate ATF134 for this engine was here: https://www.amazon.com/gp/product/B00DWFSJLC

Please check out the video and share what you think! Please also share any information you may have that would be useful for me to have next time.

Thanks for reading and watching! Please share this with your friends!

—Mark-A-Billy

Evonne: Transmission Maintenance