Nissan Patrol 4x4 (Africa)

The gearbox on my 42td makes a strange and annoying noise when I depress the clutch between gear changes. It can bbe best described as a whirling noise that last for about a second. Its not the engine, clutch or propshaft. It seems to be coming from the gearbox as I can hear the same noise when I rev the engine in neutral and depress the clutch. Is this normal on a patrol gearbox or is something going wrong. Besides this noise and some gear rattle in neutral everything is fine and smooth. Thanks in advance for your suggestions. Cheers Adrian

Lots of folks here have forgotten more than I will ever know about gearboxes, but mine doesn't do that (touch wood).

I'd first look at the throwout bearing and clutch (since it seems to happen regardless whether you are in gear or not).

agree with Mrowka, sounds like the throw-out / clutch release bearing or the spigot shaft bearing/bush . The throw-out / clutch release bearing links the clutch fork with the clutch pressure plate and the spigot shaft bearing/bush keeps the gearbox input shaft centered with the crankshaft. They are both working whenever you depress the clutch, neutral or other wise. If you start to hear the noise as soon as you touch the clutch without it being fully depressed it will most likely be the throw-out / clutch release bearing

Adrian I am not sure I understand completely, but I do not think it is release bearing. I would expect a release bearing to keep making a noise until the clutch is released again if the car is in gear.

I think the suspect is probably the spigot bearing, although it could also be one of the bearings on the gearbox input shaft. Spigot shaft is the more likely as it has no source of lubrication. Do you have any idea whether the clutch has ever been replaced? The spigot bearing is normally replaced when the clutch is replaced.

Thanks for the suggestions. I recently had the clutch replaced and it was making the same noise before the clutch replacement. Is it wise to replace the offending bearing or would one replace all the bearings while the gearbox is out? Any ideas on cost?

Adrian I have no idea what it would cost but would certainly want to replace all the bearings and syncro rings.

Pressure plate has thrown one of its petals.
The adjustment on your clutch's reach is too far

???

before replacing all, identify the culprit
Here is my view of it:

test with Engine at idle:
1) GBX in neutral - Clutch out - input shaft bearing, layshaft and bearing between input and output shaft turning. there are others turning but lets not worry about those
2) GBX neutral, clutch depressed as to take up slack, should not be able to change gears. Gears as per 1 turning as well as release bearing.
3) GBX neutral, clutch fully depressed, should be able to change gears. release bearing and spigot bearing working, gears in 1 might turn as there could be a bit of drag .
4) GBX reverse, clutch fully depressed, release bearing and spigot bearing working, gears in 1 should not turn.

results
1) normal gearbox noise - if here gearbox problem
2) if new noise, one of clutch fingers might be bent (but this normally as judder or difficult getting reverse) release bearing the culprit
3 and 4) if new noise here, then spigot bearing,
4) If noise gone , gbx input bearing or other in gearbox is the problem



On some cars teh spigot bearing might actually be a bush, I'm not sure on the PAtrol though

"I can hear the same noise when I rev the engine in neutral and depress the clutch."

Does it happen when in gear? if not I would guess your gbx input is turning a little bit but when you rev, it tries to pick up but in the end of the day the crankshaft and gbx input speed differs more due to drag of gears and oil in gbx and could indicate spigot bearing

Thanks Andries, I'll give your suggestions a try this weekend to try isolate the culprit. Cheers Adrian