Humming when 4x4 is engaged!!!!

I'm buying a used 1999 Jimny form a friend and i'm still checking some problems to know if the r that critical or can be easily handled

that car got a engine in a very good condition as we checked it the problem is a humming sound is heard when 4x4 is engaged. that sound can be heard from the front axle. it sound like a problem in the diff.
is it only diff oi problem or it means that there is a problem with front diff gears?

has the car been offroaded in the past ?

It may be that the front diff has hardly been used and is in need of an oil change / some use !!!...

Are you trying to drive it in 4x4 when on a surfaced road?

The Jimny 4x4 system should only be used on rough tracks or off-road.

Martin

it was not used for offloading before!

Are you trying to drive it in 4x4 when on a surfaced road?

yes i'm trying the 4x4 on normal road, but my wife got 2009 jimny and i ddnt hear any humming voice when i tried to engage the 4x4 on thenormal road

sounds to me like lack of use .... I wouldnt worry about it if everything is working, the hubs engage ok.

Get the diff oil changed ... and take it from there.

diff oil has been changed
i noticed that that voice is only heard when im tying the low 4wd
and its ok with the high
i tested another jimny with the same sohc and i can hear that voice when the low if engaged!
is it normal?

Sounds normal to me .... Ours Whines when in low ratio as does my fathers.