g,day everyone. i,m looking for some help with a diagnosis on my disco. she's a 96 3.9 auto. it has a rather loud whine from around 20kph to 60 kph gets louder and higher pitched as the road speed goes up, but once it settles on a set speed (say 50kph) it nearly goes away, but when you back off the throttle and start slowing down it starts whining again all the way back to 20kph. the strange thing is when its whining you can put it and netural and coast but the whining stays the same, until the speed drops down. my first guess is tranfer case, it does sound like its coming from under the drivers footwell but it could be coming from the front diff, its hard to tell, lol but i know from experiance that a car with a whining diff can do the same thing , whine on acceloration and deacceloration but not at a constant speed. any ideas/opinons would very helpful. would a different oil help to quiten it down? is it worth using any additives? thanks.....rick

 

85W140 gear lube, and some report quieting with that, some like synthetic in there. Can use in both diffs and transfer case. Because sound does not match shift points of tranny transfer case and diffs would be a good place to start.

 

Sounds like a bad diff to me, check all the fluids in both diffs and the t-case.
Also make sure someone did not use ATF in the t-case instead of gear lube, that is a common mistake.
I would not drive it until you checked the fluid levels.
The check/fill plug for the t-case is on the back at the 10o'clock position.

 

thanks guys, i should of mentioned i,ve had the disco in question for a couple of years, it has 260000 on her, ever since i,ve had it , it,s had a slight whine in the drivetrain somewhere (which is to be expected in a series 1 disco,lol), but it's slowly getting louder over time, every thing works as it should, nice and smooth gear changes , i changed the diffs and tranfer cases oil a year or so ago with what the workshop manual stated, i have cleaned the diff breathers in case they were blocked. is there any test i can do to find out if it's diff or transfer case? i will try swaping oils tomorrow, thanks for your help...............rick

 

It may be possible to remove a driveshaft and see if the sound goes away. If you take off the front driveshaft and the noise goes away, then it's coming from the front diff. Sound remains, reinstall the DS and remove the rear. After removing rear DS, see if noise goes away. Noise gone, rear diff...noise remains, must be transfer case.

Make sure you mark the driveshafts before removing as they should go back in the same position they were removed (front/back, clocking). Good luck.

 

I would go ahead and do the fluid change to the 85w140 all around. And see what that does.

 

Yeah use a heavier gear lube.

 

ok no worries, i got all the oils today, i,m going to flush the tranny and fit a new filter while i,m at it, hopeing to do it tomorrow, i,ll post with my findings ,lol , thanks everyone.

 

I am waiting for your reply... Looking to get this done to mine today if it fixes your issue.

 

Too long... Couldn't wait. Went and had the front and rear differentials oil changed. It costs around $40 for materials and labor on both ends. They also cleared the vent pipe while in there.

Drove about 20 miles afterwards and noticed no difference. They are going to do the transfer case this coming week, so maybe that will make a difference.