Allison filters - Manual is confusing?

[Trip]

In the 03 manual, pgs 7-894 & 895, includes 2 notes: 1) Don't drain the fluid if only the control main filter is being replaced, and 2) Do not replace the suction filter or seal if only replacing the oil pan or oil pan gasket.

This is really confusing. What would be the harm is doing a fluid change w/o dropping the pan when you change the spin on? My truck has aprx. 5K and I was thinking about getting the breakin oil out of there w/o dropping the pan.

On point #2, the fluid is coming out if you drop the pan. If I drop the pan, you bet I'm changing the suction filter. What am I missing here or not considering?

[schnier]

There are several ways to change the trans fluid.
1 is go to a allison dealer and have a complete flush on the trans, were they hook it up to a machine with the inlet and outlet lines hooked up to circulate all the old oil out and new oil in. Some like to go with synthetic trans fluid at this time.
2 Pull the drain plug on the trans and add about 8 quarts to replace what comes out of the drain plug on the trans. Change the spin on filter at this time, and clean the magnet on top of the filter and put it back on the new filter. Also synthetic trans fluid is possible at this time but you only change half the system as some oil is still in the torque convertor. This is what I did at 5,000 miles and again at 25,000 miles. It is very red and looks perfect with 54,000 miles on the Allison.
I have never dropped the trans pan. Just my opinion.

[77TransAm]

I think the manual is just pointing out that you can change the control main (spin-on) filter without draining the fluid. This prevents the lower-paid mechanics from working on auto-pilot and draining the fluid unnecessarily. smile.gif

BTW, Allison does recommend changing the control main filter only (not the fluid) at 5,000 to remove any assembly and/or break-in debris.

The suction filter is only required to be changed at overhaul. While I personally agree - if I had the pan removed I'd change the filter - the manual is again simply preventing someone from doing work that is not required at that time.

[sonofagun]

77TransAm has it just right.

Bob

[Trip]

son of a gun & 77transam: Thank you for the info. I just didn't understand why they said DON'T change fluid with a spin-on change. I know they recommend changing the spin-on early, but I was contemplating on a simple fluid change (w/o dropping the pan) at the same time just to remove the break-in oil. I'm old school on the suction filter though...it's being replaced at 20 to 25K with new fluid and spin-on, especially w/dino. I'm still undecided about the synthetic.

Again, thanks.

[bobojay]

The inside pan filter is a screen, not so much a filter per se. At least on '01's. When I changed mine and went to the deep pan at 15,000mi. I also changed the spin on a second time. There was no debris whatsoever on the inside pan filter (screen).
In case you didn't know yet, the deep pan takes a different suction filter. Longer pickup. Gasket is reusable. Easy change out.