Grayish tranny fluid

mquiet

Well-Known Member
Aug 4, 2009
1,500
North carolina
Boat Info
1999 480 Sedan Bridge
Engines
Caterpillar 3196
Question, I have a buddy that just checked his tranny fluid and told me it was a little grayish. Anybody have any thoughts as to a possible cause? Thanks.

Matt


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What kind of boat? What kind of transmission? When were the transmissions last serviced. ..............the answer to your question with such limited information id\s "God only knows".

If the transmission has gear coolers on them then there is a better than even chance he has a leaking oil cooler.

If the owner has a 2008 model boat and has never serviced the transmissions he may have condensate in the gear lube.
 
Sorry frank I had to reach out for more info. Ok. Boat is Hyatt, Detroit engines with twin disc tranny. The grayish material was not really in fluid but rather noticeable on dip stick when wiped and the transmission drain plug. Fluid was last changed 6 yrs ago with about 600 hours on them. Tranny is cooler my seawater similar to heat exchanger.


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fluid was changed today. looking more for possible cause. Other transmission did not have the same grayish on dipstick or drain plug. Fluid itself looked good.
 
Coolers are good for 5 years before one should look at them and at 10 replace them. 6 year old fluid I would change run for 10 hours and change again then run 50 and change again. Hoses should be looked at.
 
Frank, when I asked him about the transmission oil cooler, he said it was cooled via sea water and did not have pressure. Mine uses antifreeze. Is there a difference in regards to pressure?


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If cooled by antifreeze the pressure will be the same as the rest of that side of the system ,around 17lbs psi.No pressure with water cooled though, just flow rate.
 
So would seawater setup also need to be pressure tested? I would think you would not. So how would you know if the exchanger is any good or not? My guess is the grayish is a tiny amount of seawater crossing but how to figure it out? Thanks for some more clarification.


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Pressure testing the cooler will tell you if the copper tubes are leaking. Then you will know if seawater is getting into the oil.


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The idea isn't to test it like a radiator on a car, but to see if the oil side of the cooler will hold pressure. it is easy to do since you already have threaded connections for the oil lines.
 
Great advise. I am forwarding along. Thanks QT and Frank. Northern I also passed along your info. You all are the best.


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