Barron

I couldn't find this mentioned on any search. The Allison guy I talked to awhile back regarding a fluid change and filter on the M923A1 mentioned the Allison Polyester filter for 600 series Tranny's. it's a sort of service bulletin to change to this style in the Allison shop whenever they open the pan. I think the Napa and other aftermarket ones are paper or wire mesh. The bulletin doesn't mention the 654, but does the 653, which just has a different shift pattern, the lower ends are the same. The M923A1 has the deep pan.

The one thing I most noticed after changing the old 10Wt. motor oil out was how much smoother the shifts were, especially the downshifts. Much more enjoyable to drive in my opinion. It's definitely worth the effort to do the flush and filter.

http://www.allisontransmission.com/s...5&DownloadID=3