Loud constant hum

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

Hello there fellow Prado people

I have bought a 2002 3.0 TD prado and it came with a wonderful constant hum. The hum increases in pitch with speed regardless of road surface and doesn't go away in neutral or with the clutch depressed. I know thye Bridgestone AT's are out of shape and must contribute to this due to lack of rotation from the previous owner but could this also be a diff or transfer noise?

Not sure how to find out.

Can anyone offer some ideas?

Thanks Dave.

[Hutch Addicted PP Member Find all posts View Profile Close Hutch]

Sounds like the tyres, how many klms have they done.

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

I would guess around 40-50 thousand - they still have tread (50%)but are chipped and the surface accross the flat top is not flat ie: high and low points and inside edge wear. I have had tem rotated but nochange at all.

Thanks

[Hutch Addicted PP Member Find all posts View Profile Close Hutch]

At around those k's my bet is the tyres, they can get noisey if not looked after.

[Seththecursed Member Find all posts View Profile Close Seththecursed]

At what speed can you start to hear the "hum" ?

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

The hum starts at around 25-30 kms and at 100 it is quite high pitched and loud. Not normal for sure. Everything else is fine - car has done 226000kms. Should I change the diff oil?

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

I can also hear it almost the same on gravel if that helps?

[Seththecursed Member Find all posts View Profile Close Seththecursed]

Must be loud if you can hear it on gravel roads.

Does it change when going around corners or if you turn the wheel while driving from left to right?
Does the noise change a lot when you brake?
Does it change when you accelerate or back off?

Its hard without hearing the noise. You might have to take a mechanic or a drive line professional for a spin and let them have a listen.

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

No its just always there increases to a higher pitch with speed regardless of road surface and stays the same even in neutral. Could this be low oil in the front diff? And how would I check this?

[Seththecursed Member Find all posts View Profile Close Seththecursed]

If you remove the filler plugs on the diffs (The highest of the 2 plugs on the diff) the level should be level with the bottom part of the plug hole. Sometimes its higher and some will come out when you remove the plug especially if diffs are warm so probably best to check cold.

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

If I have to drain and fill it what oil is used? Is it just Gearbox oil ? Sorry I'm not that mechanical but I manage to get by with the right advise.

Thanks again

[Seththecursed Member Find all posts View Profile Close Seththecursed]

This is what i would use...

CASTROL LSX 90 for rear holds aprox. 2.6 Litres

CASTROL EPX 80W/90 for front holds aprox. 1.1 Litres

Others would use other brands but this is what I would use.

[portmacqarieprado Lurker Find all posts View Profile Close portmacqarieprado]

thanks I will give it a go and let you all know if it makes a difference..

[kav Avid PP Poster! Find all posts View Profile Close kav]

chuck the missus and kids outa the car see if that fixes it

[Derb Senior Member Find all posts View Profile Close Derb]

Hi Fellas. Driveshaft u-joints or out of balance drives shafts will give similar symptoms. cheers.