[rcwiegand]

I have a 2004 35 Open with 8.1 Crusaders and ZF Transmissions.  I do have trolling valves installed.  The starboard trans has always whined at idle in forward only.  Above 900 rpm or so the whine disappears.  I talked to ZF Marine and they said this is normal as that tran spins in reverse due to counter rotating engines.  It seems to be getting louder and I have seen some threads to replace tran oil with 15W-40 engine oil.  Anyone have similar issue or suggestions?

[reeltimebrad1]

I have same engine and trans but had the clatter at idle so I drained and filled with 15-40 which got rid of all the clatter but I believe might have slowed my top end speed by several mph. Replacing with 15-40 is common with the ski boat crowd but only certain transmissions and I have not seen where zf has approved a zf63a for the switch assuming that is what you have. I plan on trying 5w20 next as that's about as close to atf as engine oil gets.

[tcates1225]

Interesting because I have the same whine but only noticeable after a good run. 45 mins or so. Coming off plane and you start to hear it when you drop below 1K RPM.