Hi there. This is my first post so be gentle.


Bought a new Chevy 2500HD with D/A combo 2 months ago and love it. Read through the owners manuals. Which brings up my question.


In the Duramax suppliment manual, the 7500 mile service interval says "Allison Transmission Only: Replace the EXTERNAL CONTROL-MAIN FILTER."


The 25000 mile service interval says "Allison Transmission Only: change automatic transmission fluid and SPIN-ON FILTER if the vehicle is mainly driven ........"


I've rolled around under my truck and have seen the little red spin-on filter. But what is the External Control-Main Filter? Some past threads mention a filter inside the pan which should only be changed at overhaul. Is this the External Control-Main Filter? Should I change it at 7500 miles?


Thanks in advance.


Richard

These are both the same spin on ( little red filter ) located on the outside of the transmission. Their is also an internal screen / filter only to be changed when rebuilt. Don't forget to remove the magnet from the top of the filter and place it on your new one!


Best of luck, Fran