Strange transmission/transfer case noise....

Hi Maxwell "happy new year" from your description it could be in the rods that link the gear lever to the gearbox ..any engine vibration at idle ???? I assume that the PARK position does actually lock the transmission ?? because it is easy to shear the pin in the gearbox if you are still moving forward and select PARK.... and that might leave you with a tinkle sound when PARK is selected..also look for loose or cracked baffle plates around the engine /starter area...engine vibration at idle will set up harmonics in thin bits of metal....and why is there vibration in the first place ??? the engine will sit in a different position in PARK than when a gear is selected..with the engine switched off grab the top of the engine firmly with both hands (over the wing) and rock the engine ..you may hear the same noise.....

Hi from your last information I suspect that the noise is emanating from somewhere within the high/lo selector system.....(when in neutral everything is hanging loose)....try running the engine in Park.... select Neutral on the Hi / Lo and listen..if the noise is apparent and disappears when Hi or Lo is engaged then it is something in the Hi/Lo selector system ..is the transfer box filled with the right oil at the correct level??? or is there something like a detent spring broken in the selector mechanism ..do you get a notchy feel when you select from neutral to either Hi or Lo and a sloppy feel when in neutral???? sorry for all the questions but "Hands Off" diagnosis is not easy ..... Yes rock the switched Off engine from wing to wing... gearlever in Park... Hi/Lo in neutral........and listen

then the noise comes when there is no load or torque on the gears ie: in neutral and only when moving the gear selector lever through the reverse position (which introduces load /torque for a few milliseconds before you go into the park mode) it would seem that you may have had or have old moisture contaminated oil or very little oil in the HI/Lo box and the moisture in the old oil or lack of oil has corroded the carriers in the top of the casing for the Hi/lo selector mechanism ..hence the stiffness....take the filler bung out of the transfer box (the upper one) and poke your little finger in and down ..if low or no oil fill and drive the G' in Lo position until the oil gets hot and then drain it to the last drop and replenish with SAE 80 grade gear oil ***I am referring to the transfer box NOT the automatic gearbox which uses ATF oil. exercise the the Hi/Lo lever until the stiffness eases (best done when the new oil is hot....let the old oil if any settle in a see through container.you will be able to see the levels of contamination unless it appeared as a milky cream as you drained it then the contamination is obvious....you may have to repeat the oil change in order to clear all of the contamination.

Hi Maxwell the MB service directive (235.1) shows regular service intervals for the transfer box servicing...the box holds 2.8 ltr of SAE 80 / Hypoid 80 oil ..the recommended period for changing the oil is based on mileage but should be no longer than three year intervals......