Fixing things that aren’t broken - and now they want to send my gearbox to the factor

[scubaman]

Fixing things that aren’t broken - and now they want to send my gearbox to factory

First up apologies for yet another "my xyz is broken, help me fix it please”, but my gearbox (Twindisc MG5075-A mated to a TAMD75, 620 hours) is and I would love to hear or views on the matter.

Ever since I got the boat in 2012 there has been a lag in engaging gear on the port side (4 - 5 sec vs 1-2- sec. on stb side). We discussed this with my yard in the autumn and it was agreed that some tests would be carried out to diagnose the problem. They switched the gearbox oil pump from port side to stb and concluded that the lag transferred with it. So the port side oil pump was replaced but the problem didn’t go away.

The next step was to remove a plate from the back of the gearbox to get to a very small diameter valve to see if it was blocked. A new seal was ordered and the job carried out but that didn’t help either.

The yard has been in contact with Twindisc all along and received instructions from them. As their opinion was that while there is a lag, it doesn’t harm the gearbox and it would be safe to carry on boating as before. One of their factory experts were also due to come to Finland next week so we agreed that it would be safe to take the boat to Helsinki and have the expert have a closer look there.

So we went on our way and whilst doing a check after fifteen minutes of planing, I discovered about half a liter of oil in the bilges below the gearbox. Oil was milky, ie. full of micro bubbles (which may or may not mean anything).

On a test run, as soon as the boat was taken to plane, it became obvious that the oil was coming from the gearbox filler cap which, I believe, doubles as an over pressure relief valve.

Even after the oil in the bilge, the dipstick was still on the high mark. Their conclusion was that as the oil now is on the high mark, it should no longer be leaking from the cap at a significant rate. I know that the caps are prone to leaking so would love to hear your views on this.

The guys at the yard and at Twindisc are puzzled and want to have the gearbox sent to the factory for a proper analysis and hopefully a fix.

Sorry for the long post, but I really would appreciate your views and tips on what to check before agreeing to send the box away. I would like to drain another liter and see if the cap still leaks?

 

[volvopaul]

Re: Fixing things that aren’t broken - and now they want to send my gearbox to factor

First up apologies for yet another "my xyz is broken, help me fix it please”, but my gearbox (Twindisc MG5075-A mated to a TAMD75, 620 hours) is and I would love to hear or views on the matter.

Ever since I got the boat in 2012 there has been a lag in engaging gear on the port side (4 - 5 sec vs 1-2- sec. on stb side). We discussed this with my yard in the autumn and it was agreed that some tests would be carried out to diagnose the problem. They switched the gearbox oil pump from port side to stb and concluded that the lag transferred with it. So the port side oil pump was replaced but the problem didn’t go away.

The next step was to remove a plate from the back of the gearbox to get to a very small diameter valve to see if it was blocked. A new seal was ordered and the job carried out but that didn’t help either.

The yard has been in contact with Twindisc all along and received instructions from them. As their opinion was that while there is a lag, it doesn’t harm the gearbox and it would be safe to carry on boating as before. One of their factory experts were also due to come to Finland next week so we agreed that it would be safe to take the boat to Helsinki and have the expert have a closer look there.

So we went on our way and whilst doing a check after fifteen minutes of planing, I discovered about half a liter of oil in the bilges below the gearbox. Oil was milky, ie. full of micro bubbles (which may or may not mean anything).

On a test run, as soon as the boat was taken to plane, it became obvious that the oil was coming from the gearbox filler cap which, I believe, doubles as an over pressure relief valve.

Even after the oil in the bilge, the dipstick was still on the high mark. Their conclusion was that as the oil now is on the high mark, it should no longer be leaking from the cap at a significant rate. I know that the caps are prone to leaking so would love to hear your views on this.

The guys at the yard and at Twindisc are puzzled and want to have the gearbox sent to the factory for a proper analysis and hopefully a fix.

Sorry for the long post, but I really would appreciate your views and tips on what to check before agreeing to send the box away. I would like to drain another liter and see if the cap still leaks?

In my view there is nothing wrong with the gearbox . Have you ever done a lever calibration if not do one .
Right most of this model box pump out a little oil when up to speed out the red breathercap , what twin disc have not told you is the fact that the manifold casting isn't the right design ,on later year models it was revised to combat this problem, the reason it spurts oil out is because it can't return fast enough when the oil is thicker.
I have had this problem as a job years ago on a phantom 46 The info I'm passing on is direct help from Marine industrial transmission here in the uk. I was hold to only fill the box to halfway of the dipstick as filling it to the max mark caused oil to pump out when cruising . On another boat I carried out a mod you fitting a hose tail Union in place of the red cap , running a hose to a catch tank , this allowed the oil to expand and then drain back when the boat at rest.

 

[sarabande]

Re: Fixing things that aren’t broken - and now they want to send my gearbox to factor

ex-BP, so have some exposure to issues about oils in aircraft.

I'm looking for a source of contamination unique to the P gearbox oil.

When last changed, was a flushing oil used ? if so, was it fully removed ?

Has any gearbox component been changed, and if so was it delivered with testing or manufacturing oil in it ? (looking for cross contamination.

Was the same oil used for both boxes at the last change ? Was the P gearbox overfilled, leading to mechanical splashing and aeration ? Exactly the same oil filters on both units ?

Is there a tiny (induction) leak on the filtration side, sucking in air to cause foaming.

 

[admillington]

Re: Fixing things that aren’t broken - and now they want to send my gearbox to factor

I had a problem with gearbox oil leaking on my Phantom 46 fitted with D9-500

https://dl.dropboxusercontent.com/u/14012668/Picture 141.jpg

https://dl.dropboxusercontent.com/u/14012668/Picture 142.jpg

https://dl.dropboxusercontent.com/u/14012668/Picture 143.jpg

https://dl.dropboxusercontent.com/u/14012668/Picture 144.jpg

After several attempts and a lot of cleaning up, the conclusion was less oil in the gearbox (half way between minimum and full) and they drilled a bigger hole under the red cap to let the oil drain - that fixed it.

 

[Firefly625]

I would say scubaman listen to VP, reduce oil fill and monitor the situation and enjoy the spring.

 

[vas]

SM,

after my winter experience with my port Twin Disk box, what I learnt is that you must have oilpressure gauges for the gboxes, fullstop!
That will tell you most of what you need and warn you before failures.
The frothing and spilling is probably what VP says, so do that, but watch the gauges (hope you have them, else fit them!)

cheers

V

 

[scubaman]

Many thanks for everyone for taking the time to help me out. Here is some further info:

@volvopaul: I remember we had that discussion in 2012 and you sent me pics of the mod. One more test was made, the solenoids and the valves beneath were also switched from side to side and the yard said that as soon as the lever is put on gear, the solenoid reacts. So, they think the delay comes from the gearbox. Still, I'm going to do the calibration myself to be sure.

@sarabande: the oils on both boxes were changed over the winter and as far as I know using the same oil. The filters on both are reusable metal mesh cylinders. The oil pump was changed on the port box so it is possible that there was some residual oil in the pump that came from the factory. BUT, the oil was changed again yesterday when they removed the plate I mentioned so any contamination from the pump change should be minimal?

And yes, the port box was overfilled, would this lead to aeration and milky spillage?

@Admillington: the amount of oil is about the same albeit of different colour

@vas: Yep, sounds like the gauges are a necessity. Measuring the pressure would be the first thing the expert I mentioned above would be doing. It think a gauge is an easy retrofit.

@Firefly: I think that is what I'm going to do .

So it seems that having the spillage is a natural result of overfilling and should cure once some further oil is removed. Only oddity is the frothy oil, I suppose.

Many thanks once again for all your comments and info.

 

[rosssavage]

Is there still two problems though? The oil venting seems to have a known fix - excellent

But do you still have the delay on selecting gears?

 

[scubaman]

Yep, the delay is the same unfortunately.

One more thing to note, the oil viscosity the yard has used is SAE30 but the Volvo Penta owner's manual says it should be SAE40. Could this have any effect on the matter?

 

[volvopaul]

Yep, the delay is the same unfortunately.

One more thing to note, the oil viscosity the yard has used is SAE30 but the Volvo Penta owner's manual says it should be SAE40. Could this have any effect on the matter?

I only use 49 grade in D9 and D12 if it states and some V drive or separate base units like the Sealine T60 with C15 cats on Cardon shaft drive unit . In your colder climate 40 is too thick .

 

[scubaman]

We just did another test with the oil level half way between full and low.

This time the oil was squirting through the cap even at displacement speed which it didn't do yesterday. My engineer is now dismantling the pieces they touched yesterday to see if there is anything obvious causing this...

 

[baylabayla3288]

Regarding the delayed engagement have you checked if the delay comes from the electronics or from the gearbox. I read some where in my boat manuals that the delay is adjustable. Is the delay different when the box is cold? Is the delay the same both forward and reverse? Once my old boat started to develop a delay after longer runs when switching to reverse. It turned out to be the mechanical cable that expanded in the warm engine room just enough to only partly open the hydraulic valve on the box.

 

[scubaman]

Regarding the delayed engagement have you checked if the delay comes from the electronics or from the gearbox. I read some where in my boat manuals that the delay is adjustable. Is the delay different when the box is cold? Is the delay the same both forward and reverse? Once my old boat started to develop a delay after longer runs when switching to reverse. It turned out to be the mechanical cable that expanded in the warm engine room just enough to only partly open the hydraulic valve on the box.

Yep, it seems that as soon as the lever is set to forward-position, the gearbox solenoid both gets voltage and makes a sound so it appears that the command is relayed in real time.

 

[scubaman]

A further update. Upon taking the rear plate off it transpired that the foremost shaft in the picture below had a broken ring which could be described as a piston ring.

Now, the interesting thing is that they removed the same plate on Friday and fitted a new gasket which was identical to the old one EXCEPT for one opening between holes in the gasket around the shaft in question which allows the oil access back to the filler cap.

So, it would seem plausible that the broken ring together with the new gasket was allowing the oil to escape through the filler cap in such a significant rate. I'm hoping that by replacing the ring, this issue would be resolved.

One thing I didn't mention earlier is that if you switched gear from reverse to forward and back a couple of times in quick succession, the delay was gone. This lead us to think that there was a problem with oil pressure.

Could it be that the broken piston ring allowed the oil pressure to escape slowly and it then took time to build up enough pressure to engage the gear. But if you did it a couple of times quickly, the small crack in the seal provided by the ring didn't let enough oil to escape and the engagement was swift.

So there is a slight change that this could also resolve the delay but I may be getting ahead of things.

 

[volvopaul]

A further update. Upon taking the rear plate off it transpired that the foremost shaft in the picture below had a broken ring which could be described as a piston ring.

Now, the interesting thing is that they removed the same plate on Friday and fitted a new gasket which was identical to the old one EXCEPT for one opening between holes in the gasket around the shaft in question which allows the oil access back to the filler cap.

So, it would seem plausible that the broken ring together with the new gasket was allowing the oil to escape through the filler cap in such a significant rate. I'm hoping that by replacing the ring, this issue would be resolved.

One thing I didn't mention earlier is that if you switched gear from reverse to forward and back a couple of times in quick succession, the delay was gone. This lead us to think that there was a problem with oil pressure.

Could it be that the broken piston ring allowed the oil pressure to escape slowly and it then took time to build up enough pressure to engage the gear. But if you did it a couple of times quickly, the small crack in the seal provided by the ring didn't let enough oil to escape and the engagement was swift.

So there is a slight change that this could also resolve the delay but I may be getting ahead of things.

I'm just on with an HS63 no reverse gear, found broken rings too ,but valve block was faulty too.

Oil,is fed from the pump to the solenoids depending which service you select it pumps oil under pressure between the 3 rings down the centre of the shaft to either forward or reverse clutch drum expanding the plates creating drive.
A broken ring would give a very slow response but would also loose clutch pack pressure.
Did the engineer fit a gauge to measure pressure in each pack when gear engaged? If not he should have done this before he stripped anything off. Maybe he broke the ring when he refitted the rear casting as he must have noticed the rings prior to refitting.
I don't think there was a low pressure form the pump, more the fact the oil was going everywhere but where it was needed.

 

[scubaman]

He didn't fit a an oil pressure gauge. I don't think he has one or is familiar enough with the gearbox.

He may well have broken the ring on refitting the casting in which case replacing it wouldn't help with the delay.

Thank you for the info!

 

[scubaman]

I'm just on with an HS63 no reverse gear, found broken rings too ,but valve block was faulty too.

Hmm, do you refer to the valve that is driven by the solenoids or to the very small diameter valve in the casting itself, which iirc is behind a hex screw or something?

 

[vas]

rings and worn casing around them, lost of pressure on the plates, failure to engage fwd on port box and a few other things were discussed in the winter on my thread:
http://www.ybw.com/forums/showthrea...engaging-failure-low-hours&highlight=twindisk

If you don't mind going through 14pages, have a read... it does have a happy ending

I'd agree with VP that probably they broke the ring when refitting which they shouldn't do in the first place if they knew where to fit a pickup for a 500psi gauge and had the right bits to do it, not obvious and not the bits you usually have in your toolbox. Our boxes are very similar (at least in the way they operate) although mine's red.
Check if the broken ring was in the fwd axle, in which case maybe replacing it solves the issue, but I doubt it. All that would be obvious without even going down the engineroom with the gauges...

I was lucky to have (disconnected and fitted on the wrong spot!) the proper VDO pressure gauges, now fitted where they should be and will be connected to the RS11 or a custom arduino-< NMEA2K device in order to get them appear in the MFDs. I think you should buy two of them and find a way to fit them.
The other issue not mentioned is that of the right shimming and pretention to the conical bearings of the two main axles you see on your pics when you refit and torque the diverter valve body and pump on top. This should be checked by an expert with the right tools and looks like it's difficult to do on the spot
Of course we expect that since nothing other than the broken ring is replaced, tolerances haven't change and are OK.

good luck

V.

 

[scubaman]

rings and worn casing around them, lost of pressure on the plates, failure to engage fwd on port box and a few other things were discussed in the winter on my thread:
http://www.ybw.com/forums/showthrea...engaging-failure-low-hours&highlight=twindisk

If you don't mind going through 14pages, have a read... it does have a happy ending

I'd agree with VP that probably they broke the ring when refitting which they shouldn't do in the first place if they knew where to fit a pickup for a 500psi gauge and had the right bits to do it, not obvious and not the bits you usually have in your toolbox. Our boxes are very similar (at least in the way they operate) although mine's red.
Check if the broken ring was in the fwd axle, in which case maybe replacing it solves the issue, but I doubt it. All that would be obvious without even going down the engineroom with the gauges...

I was lucky to have (disconnected and fitted on the wrong spot!) the proper VDO pressure gauges, now fitted where they should be and will be connected to the RS11 or a custom arduino-< NMEA2K device in order to get them appear in the MFDs. I think you should buy two of them and find a way to fit them.
The other issue not mentioned is that of the right shimming and pretention to the conical bearings of the two main axles you see on your pics when you refit and torque the diverter valve body and pump on top. This should be checked by an expert with the right tools and looks like it's difficult to do on the spot
Of course we expect that since nothing other than the broken ring is replaced, tolerances haven't change and are OK.

good luck

V.

Thank you vas. I'm going through your thread at the mo.

 

[Fredrikbv]

Thank you vas. I'm going through your thread at the mo.

Scubaman, how did this problem end for you, with the oil coming out the vent plug?

I have 73-EDC machines with Twin disc MG-507 gear. BB gear gets rid of oil out through the vent plug. I have had the boat for under a year and I was told that there was a small leak on the gear when I bought it. After I changed the oil on the gear, the leakage has increased and I see oil lesning from the vent plug ( approx 2 liters after 6 hours use)