Think of the t-case as a differential, if you are driving at 50kph the diffs and t-case will be turning at the same speed, drop the trans down a gear but hold 50kph and the diffs and t-case will still be turning at the same speed as before because you did not change road speed or gears in the t-case.
Make sense?

While in any gear other than park the trans is pumping fluid, when it park it does not pump fluid.
So if you put the trans in neutral while at 50kph the trans is still turning it just is not putting out power to the wheels.

You can try this to rule out the trans, drive upto the lowest speed that it makes the noise, shift into neutral, shut off the engine.
Does it still make the noise?

With the engine off the trans will not be pumping fluid and it will just be "freewheeling", so if it is the trans the noise should stop.
If it is the t-case the noise will continue because it will still be connected to the wheels which will still be turning the gears inside the t-case.

 

And the noise is also described sometimes as a "whistle" - maybe a vac or exhaust pin hole leak?

 

g'day, no theres no whine or unusal noises coming from the engine, except for the serpentine belt squeaking from time to time when its wet.
i hope so ,lol i gave them a new filter set to fit, and all the fluids, as i had planned to do it myself (maybe i should have). could be bearings in the tranny then, sounds like i can hear my wallet screaming, lol

 

g,day, thanks, by whistle i mean it starts as a low gear whine but works its way up to a high pitch sound, i had a hr holden that use to whistle and found that it was coming from a tiny crack in the mainifold and that was loud as sin, but in this case its definitly not a engine related noise. thanks for your input.

 

g,day, yeah that does make sense, thanks thats a bloody good idea, i,ll try the engine off thing tomorrow and let you know how i went.

 

Make sure there is no one else around, and remember that you will not have power brakes or power steering.

 

cheers mate, noise stopped as soon as i cut the engine, got her booked in with the local gearbox guru in early janurary , we'll see what he rekon's, whatever he say's my credit cards gonna melt i rekon ,lol. oh well ,**** happens, would much rather know what it is, back to driving one of the sd1's i guess, or i could put my series 1 ute back on the road, would only take a battery and some fresh juice, sure the wife would love that, lol. oh well, i,ll let you all know what the outcome is later in jan, thanks guys and merry xmas and happy new year to you all..............rick

 

Best of luck Rick, Happy Holidays to you guys and keep us posted.

 

Have heard this several posts and problem has been dry swivel pin housings. There is a fill and drain plug on each, these swivel pins are also called cv joints they are the shiny ***** connecting axle to hub. Takes 85 140 gear oil. Drain if anything left and refill. There's a how to in the rave. These are notorious leakers on D1 RRC etc. Good luck!

 

re: noise stopped as soon as i cut the engine

Would not think CV noise would be ON/OFF with engine....