gearbox on Rover P4 classic

Hi,
About the manual gearbox of my Rover P4:
First gear is not synchornized. Selecting first from neutral is -somtimes- difficult (you must 'seek
and find the entrance') and sometimes very smooth.. How can this be?
Selecting reverse from neutral (without the car moving) is sometimes scratchy and sometimes very smooth again! Actually: I'm standing with the car, full depressed clutch pedal, moving from neutral to reverse: scratching (the sound of gearwheels touching), I go back to neutral and try again: no difference. When I go to neutral, let the clutch come up, depress again and try again to select reverse, everything is smooth as butter....!
First I was thinking the clutch was not coming fully free from the flywheel, but in that case it schould happen every time... Changing gears on the run is troublefree (just the problem described in the beginning of this mail.
What's going on here???
TX, rob
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> About the manual gearbox of my Rover P4: > > First gear is not synchornized. > Selecting first from neutral is -somtimes- difficult (you must 'seek > and find the entrance') and sometimes very smooth.. > How can this be? > > Selecting reverse from neutral (without the car moving) is sometimes > scratchy and sometimes very smooth again! > Actually: > I'm standing with the car, full depressed clutch pedal, moving from > neutral to reverse: scratching (the sound of gearwheels touching), I > go back to neutral and try again: no difference. > When I go to neutral, let the clutch come up, depress again and try > again to select reverse, everything is smooth as butter....!
My guess is the lack of synchro. Sometimes the gears line up, other times they dont. Pressing the clutch and releasing etc, turns the layshaft to a different position. Probably normal. (not sure about P4s but had it on other cars)
Neil
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A dragging clutch would normally drag every time, so I think you have a different problem.
My guess is that you have the beginnings of a problem with the spigot bearing (the little one in the back of the crankshaft that the gearbox input shaft runs in). Sometimes when you depress the clutch, everything lines up perfectly and smooth as butter, as you say. Sometimes it doesn't line up perfectly, and you get enough friction on the gearbox input to turn it so that the cogs on the non-synchro gears collide. The friction from the synchros would be enough to overcome the drive transmitted by a spigot bearing, so you would only notice it in the non-syncho gears.
If that is the problem, it's not going to get suddenly worse, but it's not going to magically fix itself either. And if you automatically put in a new spigot bearing when you change a clutch, a worn spigot bearing usually coincides with the clutch being well worn, so unless it really irritates you, you could leave it until the clutch starts to slip and do them both at the same time. But if you have recently done the clutch, then I'm afraid you are faced with hauling out that great lump of a gearbox again to change a tiddly little bearing. If so, look on it as a learning experience. :-)
Jim
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On Fri, 30 Apr 2004 08:45:29 +0100, "Jim Warren"

snip
Jim, is a wearing spigot bearing (isn't a tiny needle bearing?) able to give so much radial play to the shaft entering the gearbox?
As bearings of the box have to be renewed (box makes noise when in neutral, a sound which desappears when depressing the clutch pedal), the spigot can be inspected/renewed on that occasion.
TX, rob
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I haven't owned a P4 since 1973, so my memory is a bit hazy. It *might* be a needle roller, but I think it is more likely to be an oil soaked phosphor bronze thing. Over time, it the oil dries out, and then it starts to drag. It doesn't need much radial play to make a difference: the difference between a good one and absolutely knackered is only a few thou. Also, if the gearbox bearings are a bit noisy, are you sure that there is no play at the gearbox end which could affect the angle at the spigot bearing?
When you get a new spigot bearing, if it is a phosphor bronze bearing, immerse it in gear oil for at least 12 hours (preferably 24 or more) before you fit it. It will absorb some oil and last a lot longer.
Jim
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On Sat, 1 May 2004 12:22:22 +0100, "Jim Warren"

I looked in my manual/parts list again: there appears to be a 'bush' at this point of the construction. The bush-quality is not mentioned, just 'bush'.
So your mem-chips are not as bad as they could be ;-))
rob
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Aren't needle rollers for this sort of bearing a newish thing? Or at least I've not come across one on any clutch I've changed.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Wed, 05 May 2004 01:29:03 +0100, Dave Plowman

My '82 Audi 100 *has*, so it's a newish car! :-))) He should know this! :-)
rob
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You might have problems with the hydraulics of the withdrawal system - even just some air in it. Operating it a couple of times will 'pump it up' - same as with brakes.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Fri, 30 Apr 2004 09:11:12 +0100, Dave Plowman

Dave,
AFAIK this car has a mechanically operated clutch, so hydraulics will not matter here..
rob
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That surprises me. I've not owned a P4, but most cars of that age were hydraulic.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Sat, 01 May 2004 00:19:42 +0100, Dave Plowman

I checked it in my manuals.. The cluch is operated by rods and levers.. (it's a 1961 car). The brakes are hydraulic though :-)
rob
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wrote: <snip>

But designed in the late '40's with pre war technology.....
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"Bounce" off any other convenient gear, i.e. don't fully engage, just get the cones to touch. Should slow everything down inside the box enough to ensure smooth and silent selection of first or reverse.
Geoff MacK
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Clutch drag either caused by the hydraulics, a distorted or oily driven plate or just wear --- as clutches wear they don't move the working surface of the pressure plate as far clear of the driven plate.
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