Leaking Allison Filter

ausdoug · April 9, 2004

I have had my 2001 2500HD with 8.1L and Allison for about 2.5 years. I've had a slow leak (just a drop occassionally after few hundred miles from around the filter gasket) from the beginning. I've changed the filter once at 5K miles but it also leaks. It never leaks enough to drop on the ground, the drop probably blows off while driving. I have tighten the filter and it doesn't stop. Just a very minor leak around the filter gasket and it runs down and collects as a drop on the bottom of the filter. Has anyone else experience this problem?

KyleBst264 · April 9, 2004

I don't know if this is true, I have not yet changed the filter and fluid on the Allison. But anyway someone told me that there is a magnetic O-Ring that you're supposed to take off of the old filter and move to the new filter when you change the filter and alot of times mechanics and other people who change their own Allison trans filter/fluid don't know about that O-Ring.

BlackSilver · April 10, 2004

After 36,000 miles (and two filter changes) mine is bone-dry.

By the way, the magnetic donut mentioned in another post is there to collect ferrous debris, and is not an O-ring or gasket that seals anything.

ausdoug · April 10, 2004

I know about the magnetic ring. It is to collect loose metal filings/particles. It doesn't have anything to do with sealing the filter. My leak is real minor and not causing me much trouble. I'll have to investigate further if and when I remove the filter again.

jconro · April 20, 2004

The magnet doesn't help seal the filter but it does add about 1/4" or so to the mount. If you happened to forget to install it on the new filter, the difference might be enough to cause the gasket to crush to the point where it's dribbling as you describe. When I replaced mine, I went to a local Allison dealer and bought a bunch of them - I paid around $7.00 a piece which I'm assuming is less than GM wants for them. Was your replacement filter from Allison or somewhere else? That also might make a difference....