Tackling the transmission

[Kamell]

Drivetrain started making an unsettling rattle/grinding sound. Some looking around and discovered nobody in my area services these transmissions. So I pulled it and opened it up.
Found the damper plate was shot and about to fall to pieces, and had a good look at the Hurth gearbox.
New plate and seal kit on order.
Here is a shot of the clutch pack, and of you look closely you can see the textures on the clutch plates. Pretty neat.

 

[Frank Langer]

Interesting! So do you know why the damper plate was damaged? How many hours on the engine and transmission? What model engine and boat?
Is replacing the damper plate a job you can do, or are you hiring a mechanic?
I replaced the Hurth transmission on our 1984 E30+ at 800 engine hours because it was slipping unpredictably. I'm now at 3,009 hours with a Twin Disc MG340, but the damper plate has never been replaced. I'm wondering if that might become a problem at some point. Hmm...
Frank

 

[Kamell]

Was a hurth hbw 5 on a Universal 25 diesel. We started by diagnosing as best we could: ran the engine at different rpm, pushed some water and pulled some. I could hear the sound coming through the shift cable, so I was pretty sure it was a component internal or adjacent to the transmission.
The most difficult part was access; we had to remove the lazarette floor and pull most of the hoses back there. Lots of reference photos for reassembly!
Then we uncoupled the prop shaft and slid it all the way back to the packing nut and that gave us just enough clearance. We unbolted the bell housing and off it came. The unit was small enough to be managed out by one person.
Once that was off we had a good look at the damper, and could tell it was scrood.

 

[Kamell]

Frank, doing the damper plate is pretty straightforward. A replacement is around $250
I am not trained on transmissions, but it is simply a matter of reading the manual carefully and labelling everything really well. Reference photos are my Thor’s Hammer too

 

[Loren Beach]

Every mechanic that I know has advised to relace the damper ("torque") plate when you have the transmission out. Those springs have a finite life. A friend of mine once had a spring break in an older non-EY boat, and type of boat is not relavent anyway. Luckily he was idling and the spring jammed the rotation and immediately stopped the engine. He had to lift out the drive train, remove the transmission, and then change out the plate assembly. It turned into a bit of a project, as the saying goes.
Knowing about that situation was just one more reason for us to replace the whole drive train a few years ago when it became obvious we were going to have to pull the engine anyhow.

 

[brianb00]

I just got the old damper off my 25XP engine. Shown here is the damage to the splines and the look of a new damper plate (OEM). The springs were not broken. The spline shaft on the transmission looks to be in great shape. The engine is in a 1989 Olson 34 that has seen extensive hours on the ocean.

 

[brianb00]

REgarding the damper on the 25XP Universal. I am looking for a spec on torque for the Alan head bolts holding in place. Anyone have that date ? I can't find torque information in the Universal engine manual.
Thanks,
Brian

 

[Frank Langer]

Thanks for posting these pics! I can see how the splines on the new plate look clean and even, but was the wear on the old one enough to cause problems given that none of the springs were broken? How many hours would need to be on the engine to cause that kind of wear?
Although I have heard, as Loren mentioned, that people often replace the damper plate when installing a new transmission, but in the 15 years I've been following this site, damper plate problems haven't been mentioned much, so how common is this problem?
Thanks for any clarification.
Frank

 

[brianb00]

I can only estimate the hours on my engine. I have put about 20,000 miles of sailing on the boat. But, not a bunch of motoring. The original owner was on the Great Lakes and didn't sail much. So maybe at most 400 hours a year X 20 yrs = 8000 to 10000 hours. I have seen a number of damper plate discussions here and other forums, but I was looking for them . When I mentioned my forward gear issues to a neighboring boat owner he immediately said, "replace the damper plate". I heard that several times later down the marina . The symptom was simply slipping in forward gear. It slowly got worse.
Brian

 

[Frank Langer]

Thanks, Brian. That's very helpful!
Frank

 

[peaman]

I'm really bothered by the steps in the teeth of the "old" plate. It looks as if the shaft splines did not correctly match the damper plate splines. Is that possible? Or is this a normal wear pattern?

 

[Kamell]

I saw that too. I know that universals have a pretty pronounced knock on the power stroke, something to do with the very low compression and the inertia on the flywheel. This probably translates to a repetitive tapping on the splines, and as the wear gets worse the tapping turns into more of a hammering.
As with all things, it feels like problems compound on each other and worsen exponentially. I worry that my messed up damper is a symptom of some other malfunction up the line. We shall see I suppose.

 

[brianb00]

I can only estimate the hours on my engine. I have put about 20,000 miles of sailing on the boat. But, not a bunch of motoring. The original owner was on the Great Lakes and didn't sail much. So maybe at most 400 hours a year X 20 yrs = 8000 to 10000 hours. I have seen a number of damper plate discussions here and other forums, but I was looking for them . When I mentioned my forward gear issues to a neighboring boat owner he immediately said, "replace the damper plate". I heard that several times later down the marina . The symptom was simply slipping in forward gear. It slowly got worse.
Brian

I saw that too. I know that universals have a pretty pronounced knock on the power stroke, something to do with the very low compression and the inertia on the flywheel. This probably translates to a repetitive tapping on the splines, and as the wear gets worse the tapping turns into more of a hammering.
As with all things, it feels like problems compound on each other and worsen exponentially. I worry that my messed up damper is a symptom of some other malfunction up the line. We shall see I suppose.

 

[brianb00]

1. Process of getting to the damper: I wanted to mention that getting to the damper requires removing the bell housing, which requires room to slide it back. On many forums I have read about the lack of space and inability to move the prop shaft. One solution is to raise the engine and slide it forward (I have done this when I rebuilt the head). Typically others have made a vertical hoist of some type. I tried something I have only heard about and was really stoked when it worked. First the engine mount 15/16" nuts were backed off. Then the prop shaft was disconnected. I took a dock fender, deflated it, stuffed it under the oil pan longitudinally, and then slowly re inflated with a hand bike pump. The engine responded by rising. Then the rear engine mount nuts were totally removed, more pumping, and I had gained about 2" of clearance above the PSS. Off came the bell housing bolts and the transmission and bell housing were jointly slid aft. Access to the worn damper was now possible. 8 more loosened screws were removed and the errant part was out. I have now successfully re assembled the engine and should have a test run in the next two days.

2. Kamell, an acquaintance who has a Valiant 40, and has been cruising over the last 5 years, has had this same damper plate failure. He saw the pictures I had sent him. He said that his engine had the same damper, the wear on the splines was a lot worse, the springs had been worn flat along one side, and the bell housing was full of iron dust and spring shards. He has a 40 HP Perkins.

 

[Kamell]

1. Process of getting to the damper: I wanted to mention that getting to the damper requires removing the bell housing, which requires room to slide it back. On many forums I have read about the lack of space and inability to move the prop shaft. One solution is to raise the engine and slide it forward (I have done this when I rebuilt the head). Typically others have made a vertical hoist of some type. I tried something I have only heard about and was really stoked when it worked. First the engine mount 15/16" nuts were backed off. Then the prop shaft was disconnected. I took a dock fender, deflated it, stuffed it under the oil pan longitudinally, and then slowly re inflated with a hand bike pump. The engine responded by rising. Then the rear engine mount nuts were totally removed, more pumping, and I had gained about 2" of clearance above the PSS. Off came the bell housing bolts and the transmission and bell housing were jointly slid aft. Access to the worn damper was now possible. 8 more loosened screws were removed and the errant part was out. I have now successfully re assembled the engine and should have a test run in the next two days.

2. Kamell, an acquaintance who has a Valiant 40, and has been cruising over the last 5 years, has had this same damper plate failure. He saw the pictures I had sent him. He said that his engine had the same damper, the wear on the splines was a lot worse, the springs had been worn flat along one side, and the bell housing was full of iron dust and spring shards. He has a 40 HP Perkins.

A Valiant 40! A superb vessel indeed. That would be a v-drive right? How nice to be able to access the transmission from the aft cabin. But the stern tube is tucked right under the engine Sure beats doing boat yoga in the laz of my E30..

 

[Kamell]

Drivetrain started making an unsettling rattle/grinding sound. Some looking around and discovered nobody in my area services these transmissions. So I pulled it and opened it up.
Found the damper plate was shot and about to fall to pieces, and had a good look at the Hurth gearbox.
New plate and seal kit on order.
Here is a shot of the clutch pack, and of you look closely you can see the textures on the clutch plates. Pretty neat.

update:

more research and examination of the output shaft components and I noticed something. The space between the forward gear and the “thrust washer” was bigger than the corresponding space on the reverse gear. I found out the thrust washer is an integral part of the clutch system, exerting axial pressure on the gear to oppose that of the clutch pack itself. In addition: the thrust washer has a layer of bronze on its active side that performs two functions:
1) increases friction
2) wears away easier than casehardened stainless (sacrificial)
Like a brake pad, it loses function as it wears away. Eventually it fails to apply enough axial pressure and the gear starts to slip.
So there it is. I saved the cost of new clutch plates and simply have to fit a fresh thrust washer on the forward gear. Seal kit includes 2 of these washers.
Here is a pic of the old washer (still on the shaft) and the new one to show the difference in thickness, and a look at the telltale gap that pointed me to the problem.

 

[Kamell]

Drivetrain started making an unsettling rattle/grinding sound. Some looking around and discovered nobody in my area services these transmissions. So I pulled it and opened it up.
Found the damper plate was shot and about to fall to pieces, and had a good look at the Hurth gearbox.
New plate and seal kit on order.
Here is a shot of the clutch pack, and of you look closely you can see the textures on the clutch plates. Pretty neat.

update:

more research and examination of the output shaft components and I noticed something. The space between the forward gear and the “thrust washer” was bigger than the corresponding space on the reverse gear. I found out the thrust washer is an integral part of the clutch system, exerting axial pressure on the gear to oppose that of the clutch pack itself. In addition: the thrust washer has a layer of bronze on its active side that performs two functions:
1) increases friction
2) wears away easier than casehardened stainless (sacrificial)
Like a brake pad, it loses function as it wears away. Eventually it fails to apply enough axial pressure and the gear starts to slip.
So there it is. I saved the cost of new clutch plates and simply have to fit a fresh thrust washer on the forward gear. Seal kit includes 2 of these washers.
Here is a pic of the old washer (still on the shaft) and the new one to show the difference in thickness, and a look at the telltale gap that pointed me to the problem

 

[brianb00]

I have the new damper plate in. The bell housing and transmission reconnected. New exhaust riser installed. Changed exhaust to larger 2" hose to accommodate the Westerbeake stock exhaust riser - a bit of fiber glass work on the old muffler. It all rumbled to life with a slight new tone in the exhaust. A quick run down the fairway and back showed some apparent transmission slippage. The new damper makes shifting much smoother. I see a new TMC-40 transmission in my future.

 

[Loren Beach]

Good Report! and we look forward to an update on the new transmission if you do install one.
Thanks.

 

[brianb00]

Good Report! and we look forward to an update on the new transmission if you do install one.
Thanks.

The transmission is on the way. I found one in N.C. Thanks for your assistance with my questions.