Cleaning
Twin Disc Transmission Filter
Marine
Transmissions are ‘out of sight, out of mind’, and require minimal
maintenance. Better do it though – it’s a bad feeling when they don’t work,…..as
I found out years ago on a sailboat.
The AT34 has the Twin Disc MG5050SC transmission, and the AT41 has a similar
(but larger) Twin Disc transmission. The owners manual for this transmission
should have been provided with your boat, but if you don't have it you can
download it from:
http://www.twindisc.com/Downloads/Manuals/Operators_Manual.pdf
This is the rear view of the MG5050 transmission, as on an AT34. The only
difference is that Tomco plumb the oil drain directly to the Reverso Oil Change
system, and the dipstick (called ‘oil level gauge’ here !) is extended and
angled to port.
The
manual specifies to change the transmission oil and clean the strainer after the
first 50 hrs, then every 1000 hrs or 6 months.
I
usually change the oil during every second engine oil change, and with the
Reverso system it couldn’t be any easier. Check the data plate on the
transmission for type and quantity. I use Chevron Delo SAE30. It’s kinda hard
to measure the new level, so I pump all the old oil into an empty oil container,
then put the same amount or level into a similar container and pour that in.
The filter (called ‘suction strainer’!) is hard to locate but easy to
change. This can be done whether the transmission has been drained of oil or not.
If you didn’t drain the oil first, you’ll only lose about 2 or 3 spoonfuls.
NOTE:
Kurt has created a *wonderful* animated slide-show on removing/replacing this
filter on his ‘tug maintenance’ presentation. Download it from the ‘Owners
area’ on the Tomco website if you haven’t already. (You’ll need a user ID
and password for this. Contact Tomco if you don’t have one.) I really
recommend watching this animation before you do this the first time. Removing
the filter is not intuitive…
Use
a mirror to locate it on the rear port side. It is an approx 1” round disc
with a threaded hole in the middle. It has a large bolt and washer covering the
bottom edge only, that holds it in place. See the diagram above. (and yes, I
think this is a strange and insecure way to engineer an oil-tight seal - with
only partial coverage. However, its *not* under pressure. All Twin Disc
transmissions seem to work this way, and they don’t leak)
Remove that bolt (about ¾” 19mm I think), then screw that bolt into the
threaded hole. Pull like crazy to remove the strainer cover. It has a
sealing O-ring that tends to hold it
in place.
The
first time it’ll be stiff – that white paint will hold it. The strainer is
behind the cover plate – it is a gauze tube about 1” diameter and 2” long.
Hopefully
the strainer is pretty clean: if it has lots of debris its time to call your
bank manager and a transmission pro, in that order. Otherwise
clean everything carefully and put it back together. Put a little clean oil on
the O-ring to help it seal, and that’s it.
To
check the oil level, the engine must be *running* with transmission in neutral.
Anywhere between the 2 marks on the dipstick is OK.
Jeremy Bell.
AT34 #48 “Tardis”