Anyone know what this noise is?

[meerkatmag]

Hi, Transit 1988 mk3 LWB, 2.5di. I've got this loud hum that happens around 60mph and it's really loud, the recording doesn't do it justice. It's been gradually getting louder the past year or so. Anyone know what it is? Taking foot off accelerator it completely stops, foot to the floor is the loudest.
recording is here, starts around 20secs in:
https://soundcloud.com/user-764575852/t ... eird-noise

[meerkatmag]

Hi,
I guess no-one can tell what it is just from a recording! I have just grease gunned every grease nipple I can find, including the front steering knuckles (is that what their called?). Could it be a wheel bearing? I'm thinking as it is affected by throttle it's more likely a propshaft or gearbox issue. I have an overdrive but I can make the noise with the overdrive engaged or not, however it is much louder with it engaged. The gearbox was refurbished recently but I guess it could still have a fault.
Any ideas really appreciated!

[gotgcoalman]

No clue. I take it you were driving at speed?


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[meerkatmag]

It all sounds perfect until about 55mph then gets louder and louder until it starts to get quiet again about 70mph. These are speedo readings which are a bit out I think. Not sure it can actually do 70 in reality.

[weseeyou]

have you tried coasting down a long hill in neutral to see if you can hear anything ? You could get someone else to drive and you could listen around the van interior to pinpoint the noise.
I have to say it does sound like a transmission noise because if it was a wheel bearing or braking system the noise would not go away when you take your foot off the accelerator so I would check the propshaft bearings and supports first and maybe check the gearbox oil level too whilst its up on a lift .

[Mfr]

With the noise going away when you take your foot off the accelarator I would say its the Diff. I take it you have never changed the fluid? The diff's power side gear meshing makes the whine and when you let off the coast side of the gear is quite because its not as worn as the drive side. Warning if you do venture into the diff to change the oil (bit late i fear) old burnt diff oil stinks lke nothing else so make sure not to spill any! best of luck but I think you will be easier changing the back axle.
Google worn diff noise to hear some others

[meerkatmag]

It definitely goes away in neutral, it even goes away just by coasting in gear. It seems to be based on how much load is being put on the drive train.

I did suspect the diff already and drained the oil and put new oil in. I don't think it made a lot of difference to be honest. There is quite a bit back lash on the diff if that means anything.

The sound seems to come from the front to be honest, not the diff. But it's hard to be sure as the sound seems to come from everywhere.

Cheers

[Mfr]

Ah ok, if there was excessive backlash then that would cause it. Sound can run through parts and pop up almost anywhere, when my diff was whining it sounded like it was coming from the gearstick. You can get remote chassis mics to pinpoint issues.

[dumper]

Check the propshaft centre bearing as well I had one go on my mk4 in iraland on a fishing trip limped it back to my accommodation by squirting oil on it eventually the bearing exploded but I managed to get back to where I could repair it. It had been doing it for a long time like you I’d tried the diff checked all the wheel bearings but everything seemed ok .

[meerkatmag]

I'm going to spray loads of grease into the two bearings on the prop and see if that helps on my journey back. The van is supposed to have only 50k miles so it shouldn't have worn out diff surely? Hopefully just needs adjustment for back lash? Unless it's gone round the clock, 150k? Otherwise in good mechanical shape so surely not. My mechanic recently refused to do my rear brakes saying they have never been changed since new and were impossible to get drums off! So surely can't be 150k on them?

[meerkatmag]

Pic of engine, does that look like 50k or 150k miles do you think?

[meerkatmag]

The two bearings look pretty bad to me

[meerkatmag]

Backlash: https://vimeo.com/700173245/72959fde55

[dumper]

A lot of that backlash maybe in sun and planet gears I’ve had diffs out at work for loads of play and when checking the backlash crownwheel and pinion with a DTI gauge it has not been the problem I have had good results on quieten the noise by adjusting the backlash but if they had the amount of play you have work would put in a new diff.

[meerkatmag]

Anyone know where I might get a new diff or a new rear axle? I struggle to get even the simplest parts I can't imagine sourcing a whole diff. Are there companies that will rebuild them?
Cheers