strange noise /whine at around 50 mph

Hi i have a 2005 jimny with the push button transfer box . it has done 80,000 miles on road only .

Over the past year i have started to hear a whinning noise at around 50 mph if you reduce speed the whinning goes if you increase speed the whinning changes note to a higher pitch then goes compleatly when you reach 60 mph .
Lifting the accelerator momentarily seems to have no effect as also coasting in neutral .

It is hard to pinpoint the sound whilst driving but it sounds behind me rather than in front .
Has anybody experianced this or got any ideas of what it could be ?
Thanks

Hi thanks for your Help.
The oil in the rear diff i changed late last year and it had a lot of metal fillings in and also stuck to the drain plug .
When i bought the car new it was serviced by the dealler but looking at the state of the rear diff oil i would say it had never been changed .
I am on my second gerbox as the first one ,a bearing collapsed and it ate itself .
I will check the oil levels when the weather improves but from apprevious visual inspection there was no leaks .
This fault does not sound the same as the last time i had geerbox trouble .
The sound perhaps coud be better described as a wah wah sound
Sounds crazy i know .

have you checked the rear wheel bearings ????

vitara_mad wrote: have you checked the rear wheel bearings ????

You cant get enough of the rear wheel bearings can you???

Skinhead wrote:

vitara_mad wrote: have you checked the rear wheel bearings ????

You cant get enough of the rear wheel bearings can you???

there my favourate job

vitara_mad wrote:

Skinhead wrote:

vitara_mad wrote: have you checked the rear wheel bearings ????

You cant get enough of the rear wheel bearings can you???

there my favourate job

Good cus mine are sat waiting, see you tuesday

Hi I thought wheelbearings whinned at all speeds not just at one particular speed ?

treasurer wrote: Hi I thought wheelbearings whinned at all speeds not just at one particular speed ?

depends how worn it is & the whining gets louder the faster you go so its worth checking at least

Skinhead wrote:

vitara_mad wrote:

Skinhead wrote:

vitara_mad wrote: have you checked the rear wheel bearings ????

You cant get enough of the rear wheel bearings can you???

there my favourate job

Good cus mine are sat waiting, see you tuesday

did i not tell you im leaving the country for 6 months on monday

vitara_mad wrote:

Skinhead wrote:

vitara_mad wrote:

Skinhead wrote:

vitara_mad wrote: have you checked the rear wheel bearings ????

You cant get enough of the rear wheel bearings can you???

there my favourate job

Good cus mine are sat waiting, see you tuesday

did i not tell you im leaving the country for 6 months on monday

Ill be at your house at 6.00am

i can drive through the whinning and it goes at 60 mph
but thanks for your input