hydraulic gearbox wrestling.

[Guest]

Rain rain rain so pulled the noisy old gearbox apart to see why. Its a PRM 140 about 30 years old. I had the control head serviced which made the box work better. Oh yeh it was slipping, after heating up it would gradually lose drive till 2 knots was the max I could get from her ( caused by the control head having dirty oilways I think). Figured the clacking sound was actually coming from the box and pretty serious bearing noise. Gearboxes scare me a bit but someone said "just do it" so I did.

The photo is of the driven shaft, bearings on both ends need replacing. the roller bearing on the layshaft actually fell to bits, the cage was broken so this is not preventitive maintenance.

Interesting engineering, shaft with a oil line which supplies pressure to a piston which actuates the clutch, all very compact and beautifully done.

[wheels 543]

Don't shortcut on anything. Replace all seals and bearings.

Dirty oil galleries are a sign something is wrong usually.

[too_tall 15]

Dirty oil galleries are a sign something is wrong usually.

 

Or the oil has not been changed for many years - I have seen final drive oil in tractors come out as black as diesel oil that has been in for 500 hours. Either way, it needs to be done properly. Doing all seals and bearings is not a big expense if it saves you having to pull it all to pieces again in a couple of years because you left something old in there.

[Guest]

Thanks guys, good advice indeed and I hear you both. Yes when I did the first oil change after buying her it was burnt out old sh*t. I've since done three changes in a bit over a year. I'm stoked with the engineering of these.

[wheels 543]

The thing with gearboxes, especially Hydraulic boxes that have friction plates or wet clutches, is that what is in the oil tells you what is happening with wear in the box. Oil in gearboxes does not actually break down like it does in an engine and contrary to what oil sellers will tell you, oil does not need to be changed, providing it remains clean. The only reason to change the oil is that it is a way to get rid of particles in the oil. Particles come from the wearing of components and the more particles, the more the wear. But usually, once particles have started to collect in the oil to the point of being able to see them, the damage has already been done and slipping is occurring and can not be solved by simply changing the oil, unlike many Auto transmission specialists will tell you, charge you huge wads of money to give your trans a fluid change and you then find the problem remains and you end up with a big rebuild charge on top, the thieving varmints.

Keeping trans oil cool is the number one most important thing you can do. For every degree C you can reduce the oil temp, you can extend the life of the trans 10,000Km or however many hrs that adds up to in the Boat. (I work on 100hrs).

[Guest]

Yes Wheels I have recently taken the cooling system apart and sure was a problem, may indeed have been the cause of all this. The piston rings look to be good and the clutch plates also so just need o rings and bearings and should be like new, yahoo. I now know more about these systems than I could have imagined a year ago.

New head on the engine, cooling system all good with re conditioned raw water pump and now the cause of the clacking sound found. Getting there, been a long haul but satisfying in a weird sort of masoschistic manner. sh*t of a job to get the gearbox apart, arm fully extended , can't see the bolts and then don't have the strength to turn them when eventually found! I'm off to see the train enthusiasts in gissy, they have a bearing puller.

[Guest]

Ouch. Needs two new clutch packs. Quote from Moon Engines in Aukland $500 per clutch and a seal kit is $160. I can get the clutch delivered from England for $250 and the seal kit is $30!

Just now had a call from James at Moon Engines and he offered me the clutch pack at $360 plus gst. I'll get them from England!

[John B 106]

I trust James implicitly, so it makes me wonder if they are created equal.

Incidently and I meant to reply earlier, When my PRM carped the bed a couple of years ago, it was the bolts( nominal 1/4 inch) which held the clutch pack together that sheared, so I was going to suggest you replaced them regardless of appearance.

 

What does a 1/4 in nut/ bolt head remanent do to a gearbox when circulating you might ask.

[John B 106]

That was the economic option for me ,although there weren't no hundreds in the figures.

But it happened fast. Unlike the time I trusted a big brand when I shouldn't have and my boat was 2 months out of commission in 2009 because of the parts coming from England.

[Guest]

The clutch kit comes with circlips, bolts nuts springs so all good John, thanks for the advice. $3500 for a new box and I was offered $700 for my old box as a trade in so roughly $2800 or so. To completely recondition my old box is going to cost in the region of < $600. I'll be dead before it needs touching again, due to geo time.

Yes I found James at Moon Engine pleasant to deal with just too dear for me. Times are a bit tough here, our harbours has lots of vacant berths and getting more each week.

[wheels 543]

If you haven't, you need to add duty and customs and GST BBay. Plus there is no come back if you have a wrong part. James is a good guy and you would have the advantage of calling and asking advice if you bought from them.

I did say, replace everything. No short cuts with hydraulic boxes.

[Guest]

OK, Got it going today, at last! Knew I would win eventually. It was not plain sailing. I got the Clutches and the oring kit from James at Moon Engines, he came through with a good price. The bearings from the local bearing service.

I put it all back together, started the motor and tried the forward drive and nothing. So I pulled the box apart again. checked all was good, put back together and .....nothing going. No bad noises so I knew it was good mechanically. Called James and he suggested I may have placed the oil pump on upside down, can go either way so off it came again, turned it over and fired it up and yeehaaaa it goes great!!!! Thanks James.

The result is nice, much quieter engine, the clacking noise I asked about in a previous post is gone, it vibrates much less , did I mention quieter. Bliss.

[wheels 543]

Awesome. And not so scary now eh.

[Guest]

Yes I was stressed about doing this Wheels, but your right. I now know too much about PRM hydraulic gearboxes. Photo is of the driven shaft and the layshaft, you can see the clutches and the feeders near the end. One photo of the shaft as lifted from the box.