Transmission Oil Seal Leak

[mico]

A quandry,

Our Twin Disc 2:1 gearbox has just started to weep gear oil out of the rear seal. Over 12hrs at 1800RPM it dribbled about a third of an eggcup. At lower revs it dribbles less.

With 3 months left of our blue water cruise (now in Vanuatu and soon to be heading for New Cal and then back to Oz) the question is 'will it last the distance?'.

We have a new set of seals but I dont have the room to push the prop shaft back down the tube to get the gearbox off the end of our 39hp Iveco. We can however disconnect the engine and coupling and lift the engine into the cabin - big job but feasible in the water. The other option is to risk going up on the slips here in Port Villa and do it out of the water.

The alternative is to simply nurse the engine and top up the gearbox as required and do it back home in Oz.

Do gearbox seals (this has a small spring in the middle of it) just leak more as time goes by or do they have massive failures and simply dump everything into the pan.

Would appreciate any comments

Fair winds,

Mico

[MMNETSEA]

Hello MICO,

Here are couple of pictures of the TM 345 which I have 'arrowed' to confirm the location of the seal that is leaking. In the meantime I will talk to Peter Noonan at Zenith Engineering in Brisbane who installs and repairs these gearboxes. I doubt that the seal will totally disintegrate - However, the leak may be a symptom of misalignment of the engine-transmission with the propshaft's coupling, This could be the result of softening/breaking of the engine mountings. If the gearbox's output shaft is being forced out of straight alignment, the arrowed seal behind the flange will wear on one side and eventually leak. To check the alignment you will need to undo the propshaft coupling from the gearbox flange - the gap must be no greater than 1/3,000th inch - ALL the way around so that the flange and coupling are almost perfectly aligned - thereby removing any out of alignment pressure on the seal.

[MMNETSEA]

Hello Mico,

I have asked Peter Noonan if it is possible to remove the Flange from the output shaft,

so that, if possible to remove and replace the seal from the outside as opposed to taking the gearbox apart. Will let you know.

Richard

[MMNETSEA]

Mico,

In the meantime, Went through my PDF service manuals and found one for TWIN DISC transmissions - Which I can let you have if you PM me with your Email address - not able to send it via CruiserLog as it contains 86 pages.

I did copy one paragraph which appears to be common for all models :-

[sydeva]

I'm no expert, but a Swan 65 I skippered had similar problems (Volvo gearbox, high hours), and ended up sort of gluing the rear seal in place as it kept shifting out of seat, even after replaced... not a help to you i'm afraid.

[redbopeep]

Originally Posted by mico

Do gearbox seals (this has a small spring in the middle of it) just leak more as time goes by or do they have massive failures and simply dump everything into the pan.

Would appreciate any comments

Don't know about your gearbox seals at all, but can comment on ours--we had a brand new engine and transmission (Cummins 5.9 with Hurth HSW800) that was bought by the boats previous owner in more than a decade ago but never installed. We contacted the mfr (Hurth, ZF) to see what maintenance should be done before install in the boat and we learned that if the particular transmission sat on the shelf at their shop for more than 2 years they'd replace all the seals so they wouldn't leak.

Further, after talking with a tech for a bit, we learned that we should expect to replace the output seal about every 5 years--time related not wear related. Later, we met an owner of a Hurth transmission who'd just replaced an engine-to-transmission powe transmit seal..oring type thing (did the output seal at the same time) because of leaking about 3 years after it was installed (and 7 years after the transmission build date). That owner had to pull his engine forward on the engine stringers in order to get it all apart since he would have had to drop the rudder to pull the prop out the back...

We ended up buying a seal kit and replacing all the seals in the Hurth ourselves before putting it into the boat, with the assumption the seals were long past replacement date! Then, we bought another seal kit to have as "back up" in case of failure in the future. We're at least now confident that we have the tools and skills to do this particular task.

We became a little worried about our ability to replace the seals in situ as our rudder aperture is small and that huge engine would be a bear to move forward...maybe impossible given the space constraints...we ended up doing two separate things to facilitate working on the transmission. Fir

[MMNETSEA]

Hello Shaun,

Did that Zipped Pdf arrive ? If so were you able to open it ? Reason for the question is that yesterday 9 July there was apparently problems worldwide with cyberspace.

Richard

[mico]

Originally Posted by MMNETSEA

Hello Shaun,

Did that Zipped Pdf arrive ? If so were you able to open it ? Reason for the question is that yesterday 9 July there was apparently problems worldwide with cyberspace.

Richard

I think its coming through as I type although internet here in Vanuatu is pretty minimal - the natives have just gone to get some more wood for the smoke fire and I'm concerned about burning a hole in the blanket I am waving above it to get this email back to you.

[mico]

Got your pdf mmnetsea - many thanks for that. Unfortunately it covers larger gearboxes but was pretty helpful as far as troubleshooting.

I did notice that it advises NOT to use ATF oil in the gearbox while our manual (short as it is) insists that we do. Oh for clarity

At present we are being socked by rain and a strong North westerly and its a bit bouncy at anchor. I think at this stage I'll just keep topping up and make the hard call when we get to Noumea in couple of weeks or so.

The fact New Caledonia has just decided that they will no longer offer a customs entry in the Loyalty Islands means we'll have to go direct from Tanna to Noumea anyway rather then sight seeing along the way. By the time we log in I'll have a much better idea about the seal conditions, and hopefully - more facilities at my disposal in Noumea. Might even find me chewing on a crossant while I drain the oil

[Lighthouse]

Good luck Mico - keep in touch.

[redbopeep]

Hi, again, Mico,

Glad to see you're in good spirits. Definitely a go with the flow kinda guy, huh?

MM's suggestion of checking clearance all around the flange is good--do you have a set of feeler gages that will let you do this? It's good practice to check this from time-to-time and will help you verify that things aren't shifting around on the stringers, etc. If the reason the seal is leaking is bad alignment--you'd want to know quickly and fix it so you don't damage the prop shaft or put undue wear on the stern bearing/cutlass bearing.

Good luck to ya!

[Seafarer]

If you're using ATF, get a bottle of Trans-X (or something similar) and add that to your fluid. This can help the seals to swell back up and stop leaks.

I used this in a Buick once, that developed a leak where the cv-axle came out. It leaked so bad that I had to refill the transmission every couple days, but after adding the Trans-X it didn't leak a drop! Kept the car a few more months until the AC went out and then I sold it. I saw it driving around a few years later and since it's not worth rebuilding the transmission I can only assume the sealant was holding up.

If your transmission uses a chain, I'd run ATF. If it's only gears, use gear oil.

[MMNETSEA]

Mico,

Shaun what model Twin Disc ? In the meantime - only add lubricants specified by Twin Disc.

Richard

[redbopeep]

I'd not suggest using something like Trans-X as an additive, only because you don't know what it is going to do to the film thickness and viscosity of your gear lube. You can create excessive wear by not using an appropriate lube in appropriate condition.