MYSTERY ISSUE. Doing my head in. Please Help!

[PMC]

I would remove the front drive shaft and go for a drive and see if it is still there???

I have had a similar type of thing.... I think? It turned out my Auto hubs had not disengaged and although I was in 2wd I was still locked in 4wd. Worth a shot. You would not likely feel this vibe offroad so may not notice.

It would take 5 minutes to remove the front shaft and worth a drive, you could be chasing a ghost mate.

Also as MudRunner has suggested!

I just remembered that My auto hubs played up with me in Tassie in 2005 on my 1999 4.2 turbo diesel Patrol wagon. I had a prick of a grinding noise going from 40ks to 80ks. The circlip had come loose on my drivers side hub and failed to disengage causing damage to that hub. I then replaced my auto hubs with manual hubs!

PS, good call MudRunner!

Regards,

RLI

[liftlid]

Try coasting with engine turned off and trans in neutral, that will eliminate engine, your problem sounds like tail shaft, maybe slip joint, try mud runners idea also, and yes I have read the other posts.

[Evo]

G'day Evo,

If you can, choc your front wheels, jack up the rear diff so the tyres are a good inch from the ground and support with stands, leaving the jack with most of the load on it.

Start Patrol and use first to second to third and then to forth gear gentle pushing the speed up to the 6o km mark that you have been hearing the noise. Feathering the throttle, very lightly on and off to see if it makes a noise!

If it does, we know the noise is from the motor back to the rear end!

Put Patrol in neutral and apply your brakes gently to stop rear wheels from rotating, note if any noise occurs whilst braking. If noise occurs check both calipers,disks and wheel bearings.

If there is no noise, slowly get out of the Patrol whilst engine is idling and grab the driver’s side rear wheel and hear for any metallic grinding noises, do the same for the passenger side rear.

What you are doing is placing a shock load to the diff and rear wheel bearings when you grad one of the rear wheels, if a noise occurs, then we now know the noise is coming from one of these component’s. Its then a process of elimination!

1. Stop Patrol, remove both wheels. Use first to second to third and then to forth gear gentle pushing the speed up to the 60 km mark that you have been hearing the noise. Feathering the throttle, very lightly on and off to see if it makes a noise!

If there is a noise, it’s then coming from either the drive shaft or the diff.

If there is no noise, it’s then one of the rear wheel bearings.

Fit the passenger side rear wheel back on. Start Patrol whilst engine is still idling and grab the passenger’s side rear wheel and hear for any metallic grinding noises.

If there is, then then stop Patrol and refit driver’s side wheel and then remove passenger side rear wheel. Start Patrol whilst engine is still idling and grab the driver’s side rear wheel and hear for any metallic grinding noises. If there is no noise, then it’s the passenger side rear wheel bearings.

IF there is no noise coming after these tests, whilst the rear is still on stands, with another jack and another set of stands jack up the front, so the front wheels are off the ground
.
Start Patrol and engage high-range, gently engage first to second to third and then to forth gear gentle pushing the speed up to the 60 km mark that you have been hearing the noise. Feathering the throttle, very lightly on and off to see if it makes a noise!

If no noise, slowly get out of the Patrol whilst engine is idling and grab the driver’s side front wheel and hear for any metallic grinding noises, do the same for the passenger side front.

Unless you have the proper safety equipment, do not attempt jacking the front wheels. Go to a Mechanic who can perform these tests on a hoist safely.

By doing the test on the front wheels you are trying find out which wheel bearing is at fault, in a workshop environment, I would disconnect the rear tail shaft and then conduct the test, it eliminates the rear wheels being engaged and places greater load to the front diff and front wheel bearings.

Questions:

1. Did you see the mechanic conduct the tests on your Patrol? If so, did he have the vehicle on a hoist conducting simular test’s that I have just mentioned above?

2. What year is your Patrol? I do know that the synchromesh gears did play up with some of the early GU’s 1997 to 2001 4.5 petrol models. Especially third gear synchro.

3. When was the last time you did a water crossing, especially salt water?

PS, If you cannot get a friend who is mechanically to conduct the tests above safely (due to your back), then please go and ask your mechanic to perform them for you on his workshop hoist.

Regards,

RLI

In answering your questions...
1. Yes
2. 1998
3. I have only done 1 crossing, over 6 months ago, have had diff oil changed since then.

Each place I have gone to have all taken a drive, and have all except 1 have come back and done tests in the workshop.
2 of them had it on a hoist, the other 2 checked it on its wheels.

Not sure where to go from here.

Evo

[PMC]

In answering your questions...
1. Yes
2. 1998
3. I have only done 1 crossing, over 6 months ago, have had diff oil changed since then.

Each place I have gone to have all taken a drive, and have all except 1 have come back and done tests in the workshop.
2 of them had it on a hoist, the other 2 checked it on its wheels.

Not sure where to go from here.

Evo

G'day Evo,

Question: When was the last time you were off-road?

The only other explanation could be the tail shaft out of balance, check to see if the balance weights are on the shaft. Also check if you have a dent in the shaft.

PS, As previously stated, I had a prick of a grinding noise going from 40ks to 80ks. The circlip had come loose on my drivers side hub and failed to disengage causing damage to that hub. I then replaced my auto hubs with manual hubs! No more problems.

Regards,

RLI

[Dales300exc]

I get a nice grumble/growl when I forget to unlock my manual hubs and run down the highway.

Could be auto hubs.

[Parksy]

Lock your hubs and see if the noise is still there. Most simplest method to see if there is any change in noise or not.

[Evo]

G'day Evo,

Question: When was the last time you were off-road?

The only other explanation could be the tail shaft out of balance, check to see if the balance weights are on the shaft. Also check if you have a dent in the shaft.

PS, As previously stated, I had a prick of a grinding noise going from 40ks to 80ks. The circlip had come loose on my drivers side hub and failed to disengage causing damage to that hub. I then replaced my auto hubs with manual hubs! No more problems.

Regards,

RLI

Last time I was offroad was I think September last year.

Going for another drive while it's quiet.

Will report back in 30 or so.

Evo

[Evo]

Ok, so drove, listened, same thing still there. Was there with motor off, hubs locked in or free.
Gritted my teeth and Bit the bullet (got in trouble when the MOF found me under the car), pulled and pushed shafts while in neutral, got the missus to turn the wheels, play with the clutch, and found 2 things.

The rear shaft has no axial (in/out) play or no up/down/sideways movement at gearbox or diff. It does however have some slight rotational play. Is this normal?

Also, just behind the handbrake drum (on back of transmission) there is a crossmember that runs between the chassis rails, right in front of the sub tank. The tailshaft has some fresh looking rotational marks right in line with the highest point of the crossbeam under it. I tried to put my finger between the shaft and crossbeam, but couldn't squeeze it all the way into the gap. I would say the gap would be between 8-10mm
Does this gap sound too small or would the shaft distort that much to contact here?

Also, would either of these be signs of diff wear?

Evo

[nissannewby]

Yes there should be a little rotational play.

There certainly should be a bigger gap than that between shaft and crossmember. If there is fresh metal visable this could well be your noise.

If your tail shaft had half a turn of play then yes it can be a sign of wear. But it should be less than 1/4 maybe around 1/8 of a turn.

[Evo]

Yes there should be a little rotational play.

There certainly should be a bigger gap than that between shaft and crossmember. If there is fresh metal visable this could well be your noise.

If your tail shaft had half a turn of play then yes it can be a sign of wear. But it should be less than 1/4 maybe around 1/8 of a turn.

The play is a lot less than 1/8.
If this is the issue, what would cause the tailshaft to start contacting the crossmember all of a sudden, quiet smooth running, then one day, starts giving me grief...

I'm planning to look into this more tomorrow and over the weekend.

Will keep everyone updated.

Appreciate the suggestions and info.

Cheers,

Evo