ZF 63 - Water in gear case! Can it be saved?

Adefelice

Member
Jul 18, 2012
79
CT River
Boat Info
01 Wellcraft 3700 Martinique, Mercury RIB with 8hp Yamaha 2 stroke.
Engines
Twin 454 7.4 MPI Horizon
We were heading back from Block Island for our 3hr trip back home and one of the tranny's slipped 10mins from our marina. You could feel it slip and the RPM's ran up to 5K. Also noticed a trail of oil behind the boat coming out of the exhaust.
Immediately jumped into the compartment and checked fluid. It was the consistency and color of a McDonald's strawberry milkshake.
We shut that engine down and came in on one.
Once we were at the dock I pumped out all the water and rest of the milkshake.
I filled the gear case to the top with ATF and let it sit. Pumped that out, removed the oil cooler and replaced it with the port engine cooler. Each time the color and consistency were getting better.
Filled it back up with ATF and let it idle in my slip for 5 mins.
Pumped that ATF out and did it one more time.
I do have forward and revs at the dock, not sure if it will slip again at 2500 - 3000rpm.
Right now I am waiting for 2 coolers to arrive along with new hose.

In the meantime, I'll pump and dump the transmission fluid until I see normal consistency and color.
Some folks at the dock recommend kerosene (I don't feel comfortable with that) or maybe Marvel Mystery oil to help clean it out?
I know I'll get some of the best advice here and wondering if the trans is done or if I have a chance at saving it?

Also, when removing the old cooler I found pieces of an old impeller partially blocking the raw water inlet on the cooler. I'm wondering how this could be since the fuel cooler would be the first in line from the raw water pump, then the trans cooler.

454 7.4 Horizon motor with ZF 63 IV trans
 
I don't want to sound like the voice of doom here, but once a ZF transmission circulates seawater thru out the system, it is very, very difficult to save the transmission. When it began to slip water was already in the clutches and in the hydraulic system. You did what you should have done, but even with flushing and new fluid, the water and oil separate when the transmission is at rest and corrosion and surface rust has begins. Once surface rust forms, there are a number of check balls and other small orifices and parts that get sticky and stop working as they should. Even tearing the transmission down and cleaaning it usually doesn't yield a long term solution.

Hope you are lucky...........
 
Definitely not what I wanted to hear but thanks for letting me know. I was hoping for a little luck since it was going in and out of gear at the dock.
 
You need to run the boat and get heat into the gear as well as circulation of the oil now and often. Hot hydraulic fluid is a key to displacing water. Running the engine at the dock will probably not be the best way to save the gear.
Cycle the gear as many times as you can forward, neutral and reverse when running the boat.
Oil change probably 6 times minimum with running the boat.
Seems you are doing the right thing and you caught the issue immediately.
Kerosene or other quackery will probably do more damage; especially to the clutch faces.
Once you get the hydraulic fluid where it shows no indications of the water change it a couple of more times....
 
Thanks ttmott, I should have a replacement cooler by tomorrow,...hope it's not too late. I'll go back down there tonight to do another fluid change and move it in and out of gear. It's really all I can do until I get that other cooler.
Any particular brand of ATF you recommend or should I just get the cheap stuff since I'll be doing multiple fluid changes?
 
i had same problem 4 years ago with a bad cooler on my starboard transmission.
ZF 63 V Drive.
I drained refilled over 10 times.
200 Hours later it still performs fine.
Remove the filter and pump trans out by inserting hose down filter housing.
Clean the filter too with brake clean
I used the cheap Dexron 3 till it was clear.
I found numerous impeller parts in my coolers too.
On my 350 horizons first place the raw water goes through is the trans cooler i would assume yours are the same.
 
Thanks ttmott, I should have a replacement cooler by tomorrow,...hope it's not too late. I'll go back down there tonight to do another fluid change and move it in and out of gear. It's really all I can do until I get that other cooler.
Any particular brand of ATF you recommend or should I just get the cheap stuff since I'll be doing multiple fluid changes?
You can bypass the cooler to get it cleaned out (connect the two hoses together); won't hurt anything for what you need to do. You just don't want the gear too hot to keep your hand on.
 
Keep doing what you are doing. Flush it over so over. You'll be just fine.
 
Thanks guys, I knew I'd get the support I needed from this site. Always been a great resource for me.

CFD95, I can see there's a filter in the parts diagram however, I am not sure how to access it. Tools/location?
TTMOTT, I was going to bypass the cooler however, I don't have any adapters available to tie the two lines together so I just took the cooler off the other transmission for now.

I went down again last night and did two more flushes putting it in and out of gear.

New coolers should arrive today and I'll be able to run the boat later this evening. I plan to keep that temporary cooler in place for several flushes before installing the new one.

Fingers crossed.
 
filter is on top theres an allen screw in the middle of the cover.
Loosen the allan screw a few turns not all the way
Then pry cover up. Whole assembly will come out with filter.
Filter is stainless steel you can clean it with brake clean and reinstall.
When reinstalling you must push down on assembly and seat it before tightening allen screw.

Heres the service manual.

https://www.harbormarine.net/pdf/zf-repair-manual-63a-80a-85a.pdf
 
Also be sure to put the filter back the same direction. Mark the top so you remember. If upside down it will leak all over. The hole below the filter is a tube that runs to the lowest corner of the trany. It's only a fraction from the bottom so you'll get every drop that way.
 
Got it! Removed the filter and cleaned with brake cleaner. I think that made a huge improvement.
Didn't get a chance to run the boat yet, hopefully, tonight's the night.
 
Update: Ran the boat all weekend, changed the fluids after each run. Trans didn't slip at all. Each time the color of the fluid was looking more and more normal.
 
I just had this happen to me (Tranny slipped at 3600 RPMS, SmartCraft picked it up as Overspeed and shut it down immediately) on my boat with a ZF 63 IV Transmission, Checked my Fluids right away, found Port was VERY high, about 2/3 up the dipstick that only should show fluid on the bottom inch or so, pumped out 9 quarts of Strawberry Shake. New Coolers on order. Hoping all goes well, I refilled once so far, will go through the process of many changes until clean and hope for the best. Wondering if yours has held up over the past year ? I hope so, as I'm in for the same experience. Funny thing is, I had just traveled from UpState NY down the Hudson, out to Block Island and around ... 600 miles of trip. All great ! Then this happened last Saturday 3 miles from my Dock in Kingston NY. I guess I'll consider myself Lucky on location it happened at least.
 
I hesitate to I write this as I fear of jinxing myself however, I want to let you know she has been flawless the rest of last season and all of this season with at least 60 more hours on the clock.

I actually plan to do another fluid change hopefully this weekend. Funny thing,.. this tranny is actually a lot quieter than my port side?? not sure if its because of the reverse rotation.
Anyway, all is well so far,....
Could it be a Block Island thing? HAHA!
 
Thanks for the good news at the "60 hours later mark". Sounds to me like you caught it quick enough, did the proper complete flushing and now it's all OK. I got a new cooler and installed it last night, started the flushing marathon that will go on until it's clean, and then some more. Yeah, maybe it is Block Island. We had so much fun there ! We'll surely go back there many times, it was our 1st time out there, all I'm hearing now is, what week(s) are we going next year. Good feeling when everyone had fun....except my old tranny cooler, it'll never be back there. Actually was kind of scary how clogged the bad cooler appeared also, over 50% blockage. Not good. Glad I'm replacing both of them now. Again, Thanks for the good news from you ! Wishing you the best
 

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