Whirring /air type Noise when come off the power - diff or gear box?

[MisterCruiser]

So on my 120 manual gear box 5 speed cruiser, there is a whirring noise, hard to describe but I've had a friend listen with me and it's a typical diff noise.
It's very annoying, drowns out the radio a bit. I had wheel bearing noise too but replaced that and now left with this other noise.
There's nearly 300k miles on my cruiser I should probably mention.

When I'm on the throttle driving normally it's not there, as soon as I come off the throttle the noise appears and goes away again when back on the throttle. I renewed all the fluids about a year ago, have only done 1000 miles or so since, was a project and I don't use it much. All the old oils seemed ok, definitely weren't the original oils so had been changed before.

I also have a small issue with selecting reverse gear only. Sometimes it will grind when selecting, but I overcome this by selecting 1st gear first and then slide into reverse, this works fine all the time and I do it out of habit now so isn't an inconvenience. I only mention this so it can be ruled in or out as the noise source. Could there be a bad bearing in the gear box which could be the source of the on/off power noise?

Or is the on/off power noise more inclined to be the diff? It sounds like it's coming from the rear to me and my mate.

Also, my cruiser can pull harshly to the left under braking sometimes, I read when searching that a worn diff can cause such pulling amongst other symptoms. I'm happy that all my calipers / pistons are free and not seized.

Is there a way I can diagnose the noise to be the rear diff? If i remove the rear propshaft? When undersealing last year, I had both prop shafts removed for access and had them checked by a mate who repairs them and they were both ok. However, I think we did see a bit of play at the rear diff, I can't remember but my mate loosened the large nut on the rear diff for some reason where the prop shaft connects. He tightened it up again but does that nut alter the crown / pinion thing and shouldn't have been undone or does undoing that nut matter much? I'm just struggling to picture it here.

Some tip for diagnosing would be appreciated.

 

[Shayne]

Is there not a crush tube under the nut your mate loosened which when tightened to a specific torque sets diff backlash and which cannot be reused ?

I've no personal experience of this one I'm just sifting through memory of what others have posted on the forum in the past .

 

[MisterCruiser]

Yeah, I believe there is a crush washer or something, need to read up on it, never had to get a diff repaired before.

To help narrow down where the noise is coming from, I suspect rear diff, what's the best way to do this? The noise occurs when de-accelerating or lift off the power. Noise goes away when back on the throttle.

If I remove the rear propshaft and the noise is still occuring does that point to the rear diff?
Or am I better removing the front propshaft? If the noise occurs with the front prop removed does this mean it can't be any of the from components and has to be the rear diff?

If I remove the front prop do I need to put it into HL to test drive it? I believe HL will lock the centre diff?

If I remove the rear prop, do I need to put the small gear lever in a certain position or just leave alone in normal H position?

My cruiser has no electric diff lock actuators, I have no diff lock buttons in the cabin, just the small gear lever which is H, HL, N + LL.

Is it ok to drive with either the front or rear prop shaft removed or do I have to move the small gear lever into any particular position to test drive?

 

[Shayne]

Remove the rear prop and you just have a 2wd car which makes no difference to gears .

Remove front prop and you need to lock the centre diff by selecting HL and driving either way will cause no harm because you only have drive to two wheels .

When drive goes to all 4 wheels locking the centre diff on tarmac causes wind up , or undue stress because front wheels needs to move at different speeds to rear .

Take a good look at the UJ's when you have props off , they can be perfectly good for years but when they start failing it can happen over weeks or months depending on what miles you do .

 

[Shayne]

In fact before you do anything get up to speed and while looking at your rear view mirror touch your finger on it , if you get a clearer view in the mirror because you stopped a minor vibration in the mirror then UJ's are number one suspect .

 

[MisterCruiser]

WHat exactly are they referring to when saying "lock the centre diff".

There's a front and rear diff, a gear box and a transfer box. What is this centre diff, are they referring to locking the front prop shaft? Or do some folk call the front diff the centre diff? Or where is this centre diff?

 

[Shayne]

Transfer box is the centre diff , HL on the small gear stick is high locked .

 

[MisterCruiser]

Ok, that clears up the terminology at least regards the centre diff.
I have no electronic actuator locker on my rear diff or a switch in the cabin but but in the little fuse box at the drivers knee there is a "Diff 20A" labeled on the diagram and a 20A fuse in the panel, is this strange? The fact there's a fuse but no switch or locker?

I notice there is electronic actuator looking component on the transfer box with an electrical connector going to it, what is that?

Back to the issue at hand though, trying to narrow down the noise to the rear diff. If I remove the rear prop shaft, there will be no drive drive going to the rear wheels, but the rear diff will still be spinning so would the noise still be there if the rear diff is the issue even with the prop removed? Or would the rear diff not be as noisy when there is no drive going to the rear wheels?

 

[Shayne]

We all have wiring for stuff that was never fitted because factory looms are all the same regardless of spec .

If you remove the rear prop and jack up the ass end you can spin the wheels by hand which might tell you for sure its the diff you hear .

I've never done it but i'm thinking if i were in your position I'd remove the nut your mate messed with , take out the crush tube and replace it . It crushes so it cannot be over tightened and a torque wrench sets it exactly where it should be .

Has to be a vid on you tube showing the process

 

[MisterCruiser]

We all have wiring for stuff that was never fitted because factory looms are all the same regardless of spec .

If you remove the rear prop and jack up the ass end you can spin the wheels by hand which might tell you for sure its the diff you hear .

I've never done it but i'm thinking if i were in your position I'd remove the nut your mate messed with , take out the crush tube and replace it . It crushes so it cannot be over tightened and a torque wrench sets it exactly where it should be .

Has to be a vid on you tube showing the process

Fair enough the wiring being in place, but would the fuse be fitted from the factory?

I had the cruiser up on my lift yesterday, I drove it in 2nd gear whilst raised off the ground and had my mate under it listening.
When driving on my lift, 1 front and 1 rear diagonally were spinning. When I reduced speed and I could hear "a" noise, the other 2 wheels started to spin then too meaning all 4 wheels were now spinning. My mate underneath thought the noise when reducing speed, was just the other 2 wheels beginning to spin. Maybe it's normal for them to make noise when begin to spin like that? We couldn't conclusively say the noise was the same noise heard when driving on the road. Tis bit confusing.

The fact all 4 wheels were raised off the ground whilst driving on my lift has an affect on the traction / abs control, as my Abs light came on whilst doing this experiment, so driving on the lift mightn't be replica of driving on the road and hence the noise may not be the same. Whilst driving on the lift, when all 4 wheels were spinning, 2 were going forward and 2 were going in reverse direction.

However, there definitely was "a noise" when reducing speed on the lift but this was when the other 2 wheels began to spin too so I'm not sure if it was "my noise" i hear when driving on the road. I couldn't really say if it sounded the same or not, but there was noise of some description.

 

[Shayne]

Where did the noise come from ?

I imagine the 120 has traction control which basically manipulates abs so all 4 wheels off the ground would certainly confuse it .

 

[MisterCruiser]

Noise came from the rear diff. But not sure if the noise then was normal as the other wheels started spinning and maybe that was the rear diff doing it's thing so maybe that noise was normal.

But I can't say if the noise that occurred when the other wheels started to spin is the same noise as I hear when actually driving so I'm still unsure.

 

[Shayne]

Must be a good few vids on youtube allowing you to compare the noise ?

To drown out the radio its got to be alarmingly loud and the only thing i can think of is a stretched transfer box chain rattling against casing . It would be the first time i ever heard of it happening to a 120 but the late 1kd 90 series seemed particularly prone to stretching the chain .

 

[MisterCruiser]

Had another mate more familiar with stuff listen to it this evening whilst i drove it on my lift again and he said its definitely the rear diff whirring away when i back off. Could be just a bearing.
When checking for play at the rear diff with the propshaft still in place there is a slight bit of up and down play when I try to lift it, not sure what play is normal here though, I'm sure there should be some.

Will removing the prop allow me to check for play at the diff, better? As far as I remember, with the prop removed, your just looking at a big Nut, nothing to grab onto and check for play, or is there, I can't remember. Mightn't matter too much as we've already established now that the noise is from the diff.

Could just be a pinion bearing or outer bearing or something. I suppose all I can do now is bring it to my friendly local gear box repair place and see what they reckon.

Cheers for the posts, you were the only one replying lol. Folk have gotten very shy round here or maybe they're still drowning their sorrows having lost the Euro's (I'm assuming most members are UK based with my statement)

 

[Shayne]

What's the Euro's

Don't think i was much help at all but discussing these things helps us think i find .

I have only the mrs to discuss stuff with so I will mumbles through the complexities and problems with my flux capacitor and she will say something like "i need a new baking tray"

 

[MisterCruiser]

The Euro football championship, England lost in the final to Spain

 

[Shayne]

Oh right them muppets who are always crying coz they didn't get a ball each . I believe Vikings used to play a similar game only the score was more like 32 dead and 23 injured , I might even buy a ticket to watch that .