53' MY gear oil help

[David A Kern]

hi there folks.

I can't find any place on the i-net listing the specs for the proper gear oil for Allison m20 2:1 transmissions attached to my 871 naturals in my 1972 Hatteras my.

a guy on the dock said to use the same oil as I do in my engines. true or false? if false, what do I use?

[will shelton]

David, could you post your contact information....I would like to get some more of your products if you do not mind.....Thanks, Will

[David A Kern]

just emailed it to you

[David A Kern]

gear oil or motor oil, and what weight?

[RSYacht]

I'm not sure you are getting the answers you need, based upon the postings above, but the transmissions you have use a 'straight weight' (i.e. 40, NOT 10W40) motor oil - just like your engines do. We use 40 weight even in the Great Lakes climate, no problem. Based upon the temperature ranges and application I would suggest no less than 30 and no more than 40.

[dshuman]

Detroit Diesel made the Allison M20 marine gears and the two comapnies are serviced by DD. Their major service center in IL serviced my 1978 53MY the first year (so I could learn from the pro's). They used the same oil that goes in the 8V71TI engines, which was straight 40 weight. I asked the tech about that and he said that's what they always use.

[Genesis]

That is what is recommended for the Allison M series gears.

No multi-grades allowed. You can use 30wt in very cold conditions if you have creep problems with the gears cold and in neutral (I don't.)

[David A Kern]

thanks-it's truly ridiculous that this info is not available on Detroit's diesel's or Allison transmission's Internet sites. Aren't there still a million m20's still in use?

thanks

[PascalG]

the DD operator manual states on page 65 to "use oil of the same viscosity and grade that is used in the engine"

pascal
1970 53 MY

[BEC53]

I am going to change oil next week, and I wonder if I should switch to 30wt in my Allisons. Both shafts turn in neutral(cold or warm) and it is enough to cause a problem(can't release spring line without putting them in reverse). Boat is in Michigan, so no extreme temps here. Is this worth trying or is there a real problem that needs to be addressed.

[Genesis]

If its happening when hot then you possibly have a clutch pack going bad.

The cold problem is due to the viscous nature of the oil, and not due to actual clutch drag. If you really have clutch drag (if its doing it when warm) then there's a problem in the gear, but frankly, most people just live with it unless they have some other reason to pull the gear (e.g. a bad rear main oil seal, chattering or slipping in the clutches, etc)

30wt oil can be used but will accelerate bearing wear - I wouldn't do it. I run straight 40wt in mine.

[Nonchalant1]

There have been a lot of comments in other threads here about Allisons turning in neutral. Mine do to (M20s with 8v71TIs) but it's not enough to actually move the boat or tension the spring line (maybe 2 to 4 RPM). If yours are turning faster, I'd ask DD about that. They'll provide a little free advice and they really know their stuff.

[Capt Greg]

Just FYI, If you are going to change the gear oil also change the filter. There is a very high quality Stainless Steel Glass Media replacement element now available. I have been using it for a year now and the gear oil looks new. Feel free to call if you would like additional info. 1-800-348-5412 and ask for Greg