Mercruiser TRS Transmission Leak

[Blue Blazer]

We have an 1986 Hornet III with a Mercruiser TRS outdrive.

After running the boat for the first time this season, we noticed a very small amount of fluid on the outer housing of the transmission. After a closer look, we believe it is fluid being purged from the check valve. The transmission was designed for Dexron II but we are using Dexron III. The boat was serviced in Reno, NV at 4,500 Ft and run in Lake Tahoe, CA which is 6,225 Ft.

We believe the purging of fluid is due to the fact that Dexron III expands more than Dexron II.

Has anyone had this issue before?
Should we be sticking with Dexron II?
If not and we continue with Dexron III, should we be looking to replace the check valve?

Thanks!

[Pismo]

Sounds like you are very educated in these drives and know best..

[BUIZILLA]

do you have the MercTrans or the Borg Warner?

I'm not sure why your trans was designed just for DII ?

I used Type FA in my MercTrans TRS, at least for the last 10+ years, and the previous owner used it for 19+ years

[Blue Blazer]

do you have the MercTrans or the Borg Warner?

I'm not sure why your trans was designed just for DII ?

I used Type FA in my MercTrans TRS, at least for the last 10+ years, and the previous owner used it for 19+ years

The transmission is a Borg Warner.

[Ed Donnelly]

Make sure the fill cap is screwed in tight. They don't just push in..Ed

[BUIZILLA]

I have an '86 HIII with a BW as well

mine has a vent nipple on the top of the trans case that has a clear hose attached, and goes to an overflow bottle high on the transom, there is no check valve

tomorrow I will post pics of the nipple and hose/bottle

pretty certain mine is 100% original

as was stated above, the twist filler plug doesn't fit real sporty either

[MOP]

Check the level it may be just over filled and seeping out of the breather.