Noisy driveplate? - Replace it!

[RLWP]

These are from a ZF10M gearbox that came in recently. This box was showing a reluctance to go into gear.

 

The ZF10M (or the HBW100) is a mechanical gearbox with two plate clutches. This is two of the clutch plates and the forward gear wheel:

 

 

The plate on the left is from the reverse stack, the one on the right from the forward stack.

 

Comparing the drive splines we get this:

 

 

The bottom one is from the reverse stack and is pretty much as it was made. The top one is a different matter. The teeth in the spline are almost completely worn away

 

This is the forward gear:

 

 

The clutch plates work on the splines at the top, which look like this:

 

 

The plates have worn grooves into the teeth. This makes going into and out of gear tricky. The box will either not engage, or will be reluctant to come out of gear

 

These are the parts of the driveplate:

 

 

The mushroom shaped bit on the big plate has been driving the gearbox through the pegs on the small plate. What should have been happening is that the drive is cushioned by parts of the white, plastic part - which are now missing

 

So, with this metal to metal contact, any pulses in the driveline from the engine are passed straight into the gearbox. This vibration causes the gearbox input shaft to rotate with a varying speed through each revolution. The inertia in the rest of the drive (gears, propshaft, propeller) means that it wants to run at a constant speed. Net result is that the splines on the gear hammer against the splines in the plates - and wear them away rapidly

 

Not nice

 

Richard

 

More on ZF and Hurth gearboxes here: http://www.canalworld.net/forums/index.php?showtopic=60619&p=1153456

Edited January 6, 2014 by RLWP

[The Pipe]

Just looked like the drive plate on my boat in The Netherlands just a set of sharp blades. I have never been keen on R&D drive plates much prefer the Centre Flex ones.

New drive plate and Velvet Drive 73C gearbox rebuild including new inputshaft, oil pump bearings, seals and clutch pack cost €3000.

[AndrewIC]

Ouch. As per the thread I started a week or so back, I had a HBW100 which eventually failed to engage forward drive (and which ZF said, cutting a long story very short, was beyond economic repair). Now my replacement ZF10 is being reluctant to engage reverse gear. I'm thinking of replacing with a PRM, must remember to look at the plate as well.

[RLWP]

Do check the drive plate. The Hurth HBW100 is the same box as the ZF10m

 

Richard

Edited January 6, 2014 by RLWP

[Stilllearning]

A few years ago my PRM linked to a BMC1800 began to rattle in tickover, so as I was about to do a run to Llangollen and back, the drive plate got replaced. Blissful quiet and no worries after.

[Boat&Bikes]

Ouch. As per the thread I started a week or so back, I had a HBW100 which eventually failed to engage forward drive (and which ZF said, cutting a long story very short, was beyond economic repair). Now my replacement ZF10 is being reluctant to engage reverse gear. I'm thinking of replacing with a PRM, must remember to look at the plate as well.

As Richard said check the drive plate. I would also look at cable adjustment and alignment in general. I had problems with a PRM box and have come across a fair few other boats that have had trouble with PRMs. I wouldnt just accept that its the Hurth boxes failing on you. I suspect either manufacturers boxes can give problems and they are no better or worse than each other.

 

Ian.

[RLWP]

No gearbox working under adverse conditions fares well

 

Richard

[Flocal]

How much of a job is it to replace drive plate??

Talking about another problem has raised this as a possible issue.

[Stilllearning]

It should not be too difficult, but that does depend on access. Just unbolt gearbox from engine and move it backwards, then unbolt driveplate from flywheel. Then reverse of above with new driveplate. You may very well have to undo the coupling to the propshaft too.

Easy, just like it used to say in Haynes manuals about doing clutches on a Mk 4 Austin Healey Sprite : first remove engine, then unbolt clutch mechanism. The engine and gearbox had to come out in one piece first, which also involved removing the radiator!

[RLWP]

How much of a job is it to replace drive plate??

Talking about another problem has raised this as a possible issue.

 

It depends (doesn't it always!)

 

Small gearboxes like this ZF or a PRM 150 can be mounted onto an adapter plate on the back of the flywheel housing. SO to get to the driveplate it is remove the flexible coupling to the propeller shaft, disconnect the gear change linkage, remove the fixings from the adapter and take the adapter and gearbox off the flywheel housing. You should then have the flywheel and the driveplate in front of you

 

Not too bad a job, complications can be around general acces, the tightness of the flexible coupling fixings and having to push the prop shaft into the stern gland to make clearance to get the box off

 

These small boxes are quite light too

 

Richard

It should not be too difficult, but that does depend on access. Just unbolt gearbox from engine and move it backwards, then unbolt driveplate from flywheel. Then reverse of above with new driveplate. You may very well have to undo the coupling to the propshaft too.

Easy, just like it used to say in Haynes manuals about doing clutches on a Mk 4 Austin Healey Sprite : first remove engine, then unbolt clutch mechanism. The engine and gearbox had to come out in one piece first, which also involved removing the radiator!

 

And the bonnet

 

Richard

[Stilllearning]

 

It depends (doesn't it always!)

 

Small gearboxes like this ZF or a PRM 150 can be mounted onto an adapter plate on the back of the flywheel housing. SO to get to the driveplate it is remove the flexible coupling to the propeller shaft, disconnect the gear change linkage, remove the fixings from the adapter and take the adapter and gearbox off the flywheel housing. You should then have the flywheel and the driveplate in front of you

 

Not too bad a job, complications can be around general acces, the tightness of the flexible coupling fixings and having to push the prop shaft into the stern gland to make clearance to get the box off

 

These small boxes are quite light too

 

Richard

 

And the bonnet

 

Richard

Oh yes, I had forgotten that.

Not to mention the second person needed to use a length of string to lift the propshaft coupling back onto the gearbox spline inside the transmission tunnel.

[RLWP]

Oh yes, I had forgotten that.

Not to mention the second person needed to use a length of string to lift the propshaft coupling back onto the gearbox spline inside the transmission tunnel.

 

I usually manage by putting my hand down the gearstick hole in the transmission tunnel

 

Richard

[AndrewIC]

Ok, I think I've got my head round how this works after looking at the pictures in the other thread: The big gear at each end are continuously driven by the input shaft (but in opposite directions). The big gear splines drive the toothed clutch disks continuously as well, but they are in a loose stack interleaved with the "eared" plates, so there is no drive. Sliding the selector causes the stack to close up enough for the eared plates to contact the toothed plates and start spinning, and this in turn causes the balls to slide up the grooves and make the stack even tighter. Presumably the big rotatey but in the middle is keyed or splined onto the output shaft which runs through the middle.

 

If the splines are worn into grooves then the toothed disks may be reluctant to slide on the splines, so the stack doesn't close up enough to pick up drive and be forced to close up tight.

 

Is that about right?

[RLWP]

Spot on.

 

Richard

[AndrewIC]

[larryjc]

At risk of a bit of thread drift I have a Nanni with a PRM 260 gearbox that rattles for a pasttime at tickover and up to about 1000 revs which of course I need to use a lot when passing all those moored boats and in and out of locks. I have been told that a new drive plate will quiet it down but having looked at the installation today it seems a bit of a dockyard job to split off the bellhousing to change it cos the access is very tight. It was rattling all last season and didn't get any worse and also I have a double prop shaft which may make any noises louder. So I was wondering whether a thicker gearbox oil might help damp things down. PRM say to use non synthetic 15/40 - would this be an avenue worth pursuing or do I need to gird my loins and start taking things to bits?

[RLWP]

Tawny Owls PRM 260 is also on an installation where you have to sling the engine to take the gearbox off

 

Can you tie down exactly where the noise comes from? The long listening stick trick is helpful.

 

There are different kinds of drive plate. If yours is the kind with a set of springs, it may rattle anyway. Or you may have a broken spring...

 

Richard

[larryjc]

Thanks I'll have a listen but I'm pretty sure it the main box. The engine was moved forward some years ago and so there are two prop shafts with a steady bearing in the middle and I suspect that this amplifies the noise somewhat. The idea of a heavier oil was maybe it would damp any gear chatter. That said its quieter when its warmer which is when the oil is thinner but presumably the gears have expanded a bit and reduced clearances.

[casper ghost]

And just to be awkward, I used an old drive plate and removed the plastic bits leaving just a flange which was bolted on, so it's just steel on steel. The drive plate cannot really fail, though I do have a short prop shaft between the engine and this flange. It does make a noise on engaging gear but only for a second then quiet. Hope this arrangement keeps working fine for me...

Casp'

[RLWP]

Thanks I'll have a listen but I'm pretty sure it the main box. The engine was moved forward some years ago and so there are two prop shafts with a steady bearing in the middle and I suspect that this amplifies the noise somewhat. The idea of a heavier oil was maybe it would damp any gear chatter. That said its quieter when its warmer which is when the oil is thinner but presumably the gears have expanded a bit and reduced clearances.

 

They won't expand that much!

 

Richard