M20 transmission oil filter

[Yacht Jim]

I changed oil and filters on my Allison M-20 Trans today and now have an oil leak at the top of the filter cup. Attached to 8-71TI.

I assume they went together correctly - bolt w/fiber washer, through the cup, spring, spring retainer, filter. The bolt is tight when installed. It makes me think the bolt is bottoming out - as in too long. Do I need something else either under the head of the bolt or under the spring to space it out. Did not try running the other engine yet as it makes such a mess.

I have an Allison Manual as well as DD Manuals but can not find a schematic showing the assembly inside the oil cup.

As always, your help is appreciated

[davidwigler]

My M-20s have a remote spin-on filter so sorry I can't help.

[yachtsmanbill]

Are you ABSOLUTELY sure that you removed the cannister gasket and replaced it with a new one? I think the torque on that bolt is supposed to be 35 FtLbs. After the unit is assembled, you should be able to spin the cannister by hand as it contacts the gasket, then with a "tick" on the wrench it will stop spinning... then tighten. ws

[rsmith]

I always have had problems with the filter case leaking. It usualy takes that extra crank on the bolt to make it stop.

[REBrueckner]

ditto what rsmith says.... I just pulled it REALLY tight with both hands.... those can be prone to leaks according to my mechanic.

I never bothered with a torque wrench, but those are nice because of the long handle gives good leverage....and now you even know the "correct" torque...

[yachtsmanbill]

All I remember is a stud gasket, a bowl gasket and a top nut gasket. Make double sure the bowl gasket is changed and also make sure the bowl rim is true and clean. ws

[bobk]

I remember these require 65 ftlb torque. Ditto Bill's advice. My mech says the gaskets have been prone to leaking ever since they were reformulated to eliminate asbestos.

Bob

[Yacht Jim]

All I remember is a stud gasket, a bowl gasket and a top nut gasket. Make double sure the bowl gasket is changed and also make sure the bowl rim is true and clean. ws

A little clarity on the issue if you will. Your stud bolt looks like it has a thick washer on the head off the bolt. Mine does not. Also, what is the purpose of the top nut and the top nut gasket. One of my units had a top nut and the other did not. I did install new bowl gaskets and the rim is excellent. I'm thinking I do not have all the parts - definitely missing the top nut and top nut gasket. Thanks again.

[yachtsmanbill]

MY BAD!! Bear with me and grant me a little artistic license ok?? As I recall, the trans filter cannister, element and stud all screw into the to as an assembly. The nut in question holds it all together. I mistook this filter for the secondary fuel filters with a nut on the to (external).
There still needs to be a gasket under the head on the stud. The spring goes next with the element washer to follow. Then the top element washer followed by the internal nut. Now take this assembly and screw it into the filter frame.
Its yer turn to explain how difficult the gasket installation was! The old gasket is hard as a rock and will really feel like its not even in place! These usually break in one or two places upon removal. The new ones go in the same way hopefully without cracking!! They actually go into a groove in the head, and once in, should be able to rotate in that slot. Clean Clean Clean!!!
Once the assembly is screwed up into place, as I mentioned before, the filter should spin freely against the gasket. The last 1/4 inch may need to be pulled up with a wrench. Keep spinning the housing by hand as you snug it into place. Ojnce it makes contact, it will sop spinning. Its now seated. Loosen the bolt 1/8 turn and confirm this. Snug again and it will stop in its' tracks. Tighten to 65 lbs (another owner error)!
Id hate to say these are foolproof as I am a living example LOL... You have a gasket problem or a hose / fitting leak! ws






Prior to re-installing. all clean and painted

[rsmith]

I've done all that and more. I even took the cans down to a friends machine shop and put them on a precision surface and they were perfect. Like was said this all started 15 years ago when the gasket mtl was changed. I have had them dry and got a hour offshore and had oil pouring down the sides of the filter. Its so bad that I dont do them both at the same time I wait till about the second or third trip before I do the other one. Use a 6 point socket, the head is small and with the torque you need a 12pt CR socket could round it off and bust knuckles. Its a job for Snap-On.