Allison service

[Grizhead]

At 25K I took in my Duramax to my dealer for transmission service. The manual says to have the filter(s) and oil changed at 25K if used for hauling. When I picked it up I noticed that they changed one filter, I questioned the service manager and he and the mechanic stated that the transmission has only the spin on filter. Today while at the parts store I discovered that the transmission has a sump filter, is this filter supposed to be changed at 25K?

[dmaxalliTech]

Griz. Welcome to the forum

Regarding your question, the external spin on filter is the only filter that requires regular service. The internal filter is just a fine screen more so and only requires service at o/h.

The maint savy people will change the internal filter, but unless requested, most dealers will only change the external filter.

PS, where in MI are you from?