Transmission removal and replacement.

[Dominic Garofolo]

Hi all,

The transmission went on the port engine of my 31′ Bertram, roughly 6 weeks ago and I have been unable to find anybody even interested in replacing it.

The engine is a Cummins 4BTA (serial number 46043905), and the best I can tell the transmission is a Twin-Disc 5011A / 1.44:1. I am getting the transmission information from the starboard engine because the data plate on the port engine is missing. (see attached pictures). Also I am assuming that since the starboard transmission is a “RH”, that the port engine should be an “LH”.

So anyway, I have decided to try replacing it myself. Problem is I don’t know how difficult it is to remove a transmission from an engine. I realize the engine has to be supported, but after I remove all of the bolts on the transmission, should it just slide out, or is there some kind of trick to getting it off? ( locking pin, shaft key, whatever).

Any info or input is appreciated.

Thanks,

Dominic Garofolo

Topic

[Dominic Garofolo]

First of all I would like to thank both of you for answering my question. Bill—-> That is a lot of good information, thank you!

Now for the odd but good news:

I went into the local Marine store here in Cape May to buy some penetrating oil, and ran into an old timer who asked me what I was using it for. I explained what had happened, and he said, “take off the mushroom cap and then try it”. Further he said it sounds like the transmission is air locked, or air bound. (something like that), and to check the suction screen.

So, (I am the kind of person who will try anything at least once.) I go back to the boat and look for something that looks like a mushroom on the transmission. The item that I found was some sort of air admittance valve (see photos below). It was filthy and it was stuck closed.

So being a good listener I started the engine with the air admittance valve removed and attempted to put the boat in gear. Believe it or not the boat immediately went into forward. I then tried reverse, same thing, the transmission immediately went into reverse. I then tried forward again and it worked again. Did this several times and everything worked like it was suppose to.

My next move was to see if I could disassemble the valve and clean it. This was accomplished easy enough, and once it was clean I reinstalled it, started the engine and put the engine into gear and nothing…. No forward and no reverse. CRAP, what now?

So I took the air admittance valve off of the other engine (which was in much better condition), and tried again. And nothing! Now what?

I know, I’ll check the suction screen. I removed the suction screen plug not knowing what to expect. I stuck my pinkie into the hole and found that the suction screen itself was collapsed. After a couple of minutes with a pair of needle nose plyers I was able to get the screen out. It was really jammed in there. I put it around a 1/2″ breaker bar I had in my tool box, made sure it was clean and reinstalled it. Started the engine, shifted into forward and the transmission worked again.

I then changed the oil a couple of times because it was very black, and then took the boat for a test ride. The boat ran great! On Monday I called Twin-Disc and ordered two new air admittance valves and two new suction screens.

What I find amazing is that every mechanic I talked to told me the transmission was shot and needed to be replaced, yet no one would come out and look at it. And if it wasn’t for the older gentleman I ran into I would be pulling the transmission, for no apparent reason.

I guess sometimes you get lucky.

Thanks again Tony and Bill.

P.S., Bill I wouldn’t know what a torsional damper is if it hit me in the head LOL.

1 user thanked author for this post.

donald roth

[Bill Fuller]

Before you get too far along, are you sure the problem is the transmission itself?
What were the symptoms when it failed?
Could the problem be the torsional damper (drive plate). Plus, while you have the trans out, I would replace the torsional damper at the same time.

so far as removing:

Get everything that is even remotely in the way out of the way.
Remove the shift linkage.
Remove the transmission cooling lines.
I am not familiar with your setup, but you may need to remove parts of the exhaust and the turbo to have room for removing the transmission. Don’t try to work around these types of these things, it just makes the job a lot more difficult.
Remove the bolts on the shaft coupler and separate the shaft from the trans. Be careful not to let the prop hit the rudder.
Loosen the bolts that hold the transmission to the bell housing, do not remove yet.
Remove the Nuts that hold the engine/trans mount on the trans to the motor mounts on the boat (does that make since?)
Lift and support the engine with blocks, you may have to loosen the front motor mounts to do this. Make sure you are high enough to clear the rear motor mounts.
While supporting the transmission, remove the bolts that attach it to the bell housing.
Slide the transition back and lift out. See Tony’s remarks about rust.
Then remove the bell housing and the torsional damper, if you decide to do this.

For lifting, I use a very small chain hoist and a 4×6 across the gunnel. This works well on my Bertram 28.

So any of you guys that want to had things to this quick list please add on.

Bill

[Tony Athens]

Where there is a will, there is always a way.. Seems like you have it!

The only thing that would hold it from sliding back once all the adapter bolts are removed (12 of them around the bell housing), is RUST between the spline and the torsional coupling… Sometimes, that really becomes the ISSUE,–You be able to come back about 1/4 to 1/2″ and then it will not come any further–Then you know that is the issue…………………………….Assume the gear weighs about 90 lbs and you’ll need 4″ minimum for the “slide”

Sounds to me like you definitely are ready to “take in on”.

Good luck, but do come back with what you sort out so you can help others, of you you get stuck–We’ll work it out..

Tony

[Dominic Garofolo]

Thanks!
Makes me feel a little more confident.

DG

[Tony Athens]

Access to the gear, rust both externally and inside the engines bell housing, and of course, your motivation and skill are the big factors.. Yes, if it’s not rusted together ( spline to torsional coupling). it will slide back..

Tony

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