Transmission locks when rotated by hand

[Dave sonksen]

Have twin 6btas 330 with ZF transmission. When having the bottom painted and the props repitched noticed that the transmission will lock when you rotate prop shaft slowly and will unlock if you reverse it and Turn again. Turns freely otherwise until it locks again after more rotations. Transmission is in neutral when this is done. Does not seem to be a problem when the engines are running and I’m driving the boat. However, several months ago on a trip to Catalina at about 15 kt seemed to hit something on that engine for a second. The boat or that prop hesitated for a second but then went on OK. That was about 40 hours of operations ago. No symptom of the problem since then until the fellow removing the props pointed it out to me several days ago. Is this condition normal? Could it be a clutch issue or debris between the gears that falls loose when you reverse it.

Topic

[Tony Athens]

Not sure where I came up that you had a ZF220A — Sorry for the goose chase….

Does your data tag on the gear tag say ZF63A, or it that a guess, or from a survey………………………………..That would not be a normal OEM supplied gear for that engine..

Regardless, we’ll need to all re-think this issue as now things are way diffenent

Tony

[Rob Schepis]

To my knowledge the 80’s and 85 have the drain plug, the 63 does not. You could try but you will not have much room to work through the suction hole to do what you say, I think the max tube that fits down there is ~5/8″ but don’t quote me on that…

[Dave sonksen]

63 A with metal mesh filter

Thank you very much for the link to that other topic. I’m starting to feel comfortable in addressing this problem. From what I see on the other link the way you drain the oil is to suck it out with a pump rather Releasing it from a drain plug. Do you think it is possible to put one of those strong magnets down there on the end of a stick after you remove the filter and that may pick up larger debris( like a broken gear tooth) .I assume there is no drain plug.

[Rob Schepis]

Dave sonksen wrote:

It is a 63 A

In that case you’re not going to have the screen behind a 36mm hex as in Tony’s pic above.. you have the drop in metal mesh filter.

See this link:

https://www.sbmar.com/community/topic/newbie-trans-questions/

[Dave sonksen]

Zf model

It is a 63 A

[Tony Athens]

Dave,

Have a mechanic pull the drain plug and the screen.. In other words, drain the oil into something that can be inspected, and when you pull the screen, BE THERE for the 1st look before he screws up what needs to be looked at… ..

Maybe $150 for this service max?

As to a chipped tooth–Running easy, it could easily go “for ever” and you never know the difference.. Personally, if that is how you run and you do not find anything in the screen or in the “drained” oil, I’d forget this entire episode and “go fishing”…..

FYI, I’m an ” ol’ guy” too and understand exactly where you are coming from……….

Tony

[Rob Schepis]

Again —— What model ZF ?

[Dave sonksen]

Assuming a chipped tooth

Assuming that it is a chipped tooth, why would that cause the prop shaft to lock when rotated and then Unlock when you reverse it a little bit. Why doesn’t it lock on every rotation or at least every rotation of the larger of the two gears that are engaging. Sometimes it locks after one rotation sometimes after eight or 10 rotations but always unlocks when reversed less than 1/4 of a rotation. Mechanic says $2500 to remove transmission and tear it down. I don’t know how to judge that number. Tony said remove the plug and look at the screen. Does that involve removing the transmission oil. Thanks for all of the help and ideas that this forums members have given to me already! Means a lot to an old guy. I wonder how long this transmission would last at hull speed.

[Rob Schepis]

Philip wrote:

And the most common insurance claim is hitting something, so might be worth documenting very carefully. Insurance might end up being involved in hauling, dry dock, and repair bills.

Good advise from Philip and be sure to follow it. Be prepared for the fact that getting insurance company to commit to driveline damage from striking foreign object without a damaged prop can be a real chore. A blade, or two, could be out but not enough to be visible simply looking at it. Get it scanned but do not repair it…. if this becomes an insurance claim that bent prop will be your “evidence” so don’t spoil it…

And, unless I missed it, I don’t see where you’ve stated what model ZF ?

[Philip]

What did the prop look like on that side? Was there any nicks or dings in the prop?

You mention “ seemed to hit something”? Any idea what? Even a piece of kelp can ding a prop…. any vibrations afterwards that were not there before?

And the most common insurance claim is hitting something, so might be worth documenting very carefully. Insurance might end up being involved in hauling, dry dock, and repair bills.

[Tony Athens]

Anything can be repaired.. It comes come to “is it cost effective”.. ……………Pull that screen and plug for a peek..

Tony

[Dave sonksen]

Transmission locks

If it is a chipped tooth can the transmission be repaired.

[Tony Athens]

I would guess a chipped tooth ? That’s a tough one to diagnose…

Pull the screen/magnetic plug and see what it has in it..

Tony

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