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Old 02-02-2012, 19:33   #1
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Replacing a Damper Plate on My Transmission

I have a damper plate with worn out springs on my Hurth transmission it is coupled with my 40hp Universal. I am wondering how difficult it would be for me to replace this plate myself.

What are the steps I would need to take to remove the transmission? Could I hypothetically do it while I am still in the water? I worry about undoing the coupling and moving the shaft in an awkward way that might damage or tweek the stuffing box.

What does it take to reinstall a transmission? Do I need to realign it in any way with the flywheel or do I just bolt it right on?
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Old 02-02-2012, 19:50   #2
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Re: Replacing a damper plate on my transmission

I've taken the hurth trannie off my Perkins 4108 a few times--mostly to replace the rear oil seal. It wasn't hard and the transmission was surprisingly light--I think it was a 125 and weighed less than 40 pounds.

On the Bendytoy, there wasn't enough room to slide the shaft back and get the trannie out, so I took off the back two engine mount nuts, loosened the front, and pulled the back of the engine up so that the trannie would clear the coupler.

Removing and replacing the transmission was pretty much a matter of removing the controls, then unbolting it and sliding it off. Fitting it is the reverse, with no difficult alignment issues.
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Old 02-02-2012, 19:53   #3
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Re: Replacing a damper plate on my transmission

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Originally Posted by donradcliffe View Post
I've taken the hurth trannie off my Perkins 4108 a few times--mostly to replace the rear oil seal. It wasn't hard and the transmission was surprisingly light--I think it was a 125 and weighed less than 40 pounds.

On the Bendytoy, there wasn't enough room to slide the shaft back and get the trannie out, so I took off the back two engine mount nuts, loosened the front, and pulled the back of the engine up so that the trannie would clear the coupler.

Removing and replacing the transmission was pretty much a matter of removing the controls, then unbolting it and sliding it off. Fitting it is the reverse, with no difficult alignment issues.
Instead of moving the shaft you moved the whole engine? You are a sick man sir!
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Old 02-02-2012, 22:02   #4
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Re: Replacing a damper plate on my transmission

Not when the propshaft will only slide back an inch until the coupling hits the packing gland.
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Old 02-02-2012, 22:43   #5
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Re: Replacing a damper plate on my transmission

My only issue is that I have a v drive, so the coupling has to come off to remove the transmission. I guess I need a gear puller for that?

When I had the shaft out, I took the transmission and damper plate off and replaced the damper plate. Ridiculously easy. Just a few bolts (assuming none are seized) and it's all dry and clean and easy. No alignment or anything (though may as well check your engine alignment once you're done. Gotta check it every once in a while anyways)
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Old 03-02-2012, 03:05   #6
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Re: Replacing a damper plate on my transmission

I took out the damper of our Volvo MD-22L w/MS2 transmission (straight axle) in middle of the season last summer. As I had never done it before, I was a bit nervous to do it. On the end, it was not a hard job at all. I had to (1) disconnect the shaft from transmission and slide the shaft backwards, (2) open the bolts and remove the transmission, which was surprisingly light, (3) support the engine, as its mountings were attached to the rear part of the engine body which had to be taken off to access the plate, (4) remove the rear part of the engine body, and finally (5) remove the damper plate.

You can do it all in the water - just do not push the shaft all the way through! The shaft slides back and forth just nicely with little effort. If it has a flange coupling, just decouple the flange. That way the shaft cannot slide out unintentionally. Unless you drop something heavy on the shaft (like the transmission) or hit it hard, you should not be able to damage the stuffing box. Also pay attention not to break anything when you tighten the screws. On my Volvo, both the engine and transmission bodies are made of alloy cast. There is no need to use extreme forces. If you can, check out the manufacturer’s specs and tighten accordingly.

The only hard part was some screws and bolts that were very reluctant to open after sitting tight for 15 years. Some bolts were also very hard to access to begin with. I suggest you start the work a couple of days earlier that you planned by spraying the screws/bolts/nuts with a product made specifically to release them. Should you break a screw deep somewhere that is hard to access and you maybe even have no visual would be a major and unnecessary trouble to overcome.

On our case, the whole thing was an unnecessary exercise. The damper place was perfectly all right. It was actually the rear engine mounts that had given up. The shaft was thus aligned too low and was able to hit the stuffing box if the engine for some reason vibrated too much. To fix it, I bought new engine mounts and realigned the entire drive line. The original damper plate is still just fine after 4500 hours of usage.
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Old 03-02-2012, 03:19   #7
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Re: Replacing a damper plate on my transmission

I replaced the damper plate that fit from a perkins 4.108 and a velvetdrivre about 2 years ago. Because of the cramped space it was a fairly difficult job, but not impossible for a mechanically inclined sailor who wants to save about $2000 in charges. I wrote an article about the repair and it was published in God Old Boat, March 2011. If you would like a copy mailed, email your address and I send it on. Bob Tigar bjtigar1@netzero.net
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Old 03-02-2012, 06:43   #8
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Re: Replacing a damper plate on my transmission

How do you know the damper plate is bad? They last a very long time. Is there a rattling sound at idle? Very hard thump into gear? Like the poster above mentioned, check the mounts and also the coupler, flywheel bolts and stuff bolted to the engine first.

However, if you want to replace the damper plate just as routine, it is relatively inexpensive and easy to do if you have access to the transmission.

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Old 03-02-2012, 07:05   #9
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Re: Replacing a damper plate on my transmission

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Originally Posted by colemj View Post
How do you know the damper plate is bad? They last a very long time. Is there a rattling sound at idle? Very hard thump into gear? Like the poster above mentioned, check the mounts and also the coupler, flywheel bolts and stuff bolted to the engine first.

However, if you want to replace the damper plate just as routine, it is relatively inexpensive and easy to do if you have access to the transmission.

Mark
I have very good access to my engine and transmission. I am assuming it is the damper plate through process of elimination. I have a good diesel mechanic friend who went through the entire engine with me to source the sound we were hearing. It was a clack clack clack at low rpm when you put the engine in gear. We checked the alignment, replaced the cutlass bearing, and looked and listened all around the engine. Then we read the manual, ha ha. And it said, for one thing, "set the idle above 900 rpm lest your damper plate will go clacketty clack."

Well we raised the idle and it all but fixed it. Still below about 1300 rpm you can still hear it a bit. So my thought is that the PO had been running the engine at too low and idle and had prematurely warn down the plate. I am about to set off on a big trip and would like to fix it before it gets really broken.

Make sense?
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Old 03-02-2012, 07:24   #10
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Re: Replacing a damper plate on my transmission

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Originally Posted by unbusted67 View Post
I have very good access to my engine and transmission. I am assuming it is the damper plate through process of elimination. I have a good diesel mechanic friend who went through the entire engine with me to source the sound we were hearing. It was a clack clack clack at low rpm when you put the engine in gear. We checked the alignment, replaced the cutlass bearing, and looked and listened all around the engine. Then we read the manual, ha ha. And it said, for one thing, "set the idle above 900 rpm lest your damper plate will go clacketty clack."

Well we raised the idle and it all but fixed it. Still below about 1300 rpm you can still hear it a bit. So my thought is that the PO had been running the engine at too low and idle and had prematurely warn down the plate. I am about to set off on a big trip and would like to fix it before it gets really broken.

Make sense?
Yep, makes sense. There is nothing really to "wear down" on the damper plate, but the springs could be loose or the bushing or spline loose.

Since you have good access, replacing it is very easy. Depending on your particular transmission and engine combo, you will either unbolt the transmission or remove the bell housing with the transmission attached to it. The damper plate is bolted to the flywheel. Unbolt it, put the new one on, reconnect the transmission and you are finished.

You will need enough space between the transmission and the flywheel to get a wrench and your hands in there - so maybe 12"? Just disconnect the shaft coupling and support it with a piece of rope from above or a block of wood from below to keep it nominally in place. If you have enough room to move the shaft backwards, that will be helpful. If not, just work around it.

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Old 03-02-2012, 07:29   #11
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Re: Replacing a damper plate on my transmission

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Originally Posted by colemj View Post
Yep, makes sense. There is nothing really to "wear down" on the damper plate, but the springs could be loose or the bushing or spline loose.

Since you have good access, replacing it is very easy. Depending on your particular transmission and engine combo, you will either unbolt the transmission or remove the bell housing with the transmission attached to it. The damper plate is bolted to the flywheel. Unbolt it, put the new one on, reconnect the transmission and you are finished.

You will need enough space between the transmission and the flywheel to get a wrench and your hands in there - so maybe 12"? Just disconnect the shaft coupling and support it with a piece of rope from above or a block of wood from below to keep it nominally in place. If you have enough room to move the shaft backwards, that will be helpful. If not, just work around it.

Mark
Nice thanks. Hey, is the damper plate/flywheel inside of the bell housing?
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Old 03-02-2012, 08:02   #12
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Re: Replacing a damper plate on my transmission

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Nice thanks. Hey, is the damper plate/flywheel inside of the bell housing?
Yes. The flywheel and damper plate are actually part of the engine assembly and not the transmission assembly. Many of the small Hurth gearboxes bolt to a bell housing from the inside, so to remove them you must remove the bell housing. The bell housing is only a cover for the flywheel and doesn't have any real function in regards to the engine or transmission other than something to mount to.

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Old 03-02-2012, 08:08   #13
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Re: Replacing a damper plate on my transmission

Here is a picture I got off google of an engine with the transmission removed (this one doesn't have a bell housing). You can see the flywheel with the damper plate attached and the starter on the side.

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