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!
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???
> 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!
> 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
A dragging clutch would normally drag every time, so I think you have a
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. :-)
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.
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.
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 ;-))
"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.
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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