I am coming due for an oil change and I was going to change the front and rear differential gear oil and the Transfer case fluid as well. I know that the front is listed as SAE 90 rear 85W90 and transfer case is Dextron III ATF. I was thinking of going synthetic on all three. I know that synthetics handle contamination with water better than dino oil. (I have to ford some creeks getting to my favorite hunting spots usually only about 12" of water) I already use Mobil 1 0W40 motor oil and have been happy with their oil so my intention was use all Mobil 1 fluids. But Mobil one only lists a 75W90 and 75W140 for their synthetic gear oil. Will one of these be ok in the ML? Are there other synthetic gear oils that would be better? Mobil has a synthetic Dextron III ATF so that is not a problem. Mine is a 98 ML 320.

Thanks,

When I changed my front and rear diff. oil at I think it was 75K miles it looked suprisingly good, like I really did not need to change it. It was hardly discolored at all. I replaced it with dino oil. I heard but I don't remember where that it was best to use dino oil in the diffs. I also used regular non synthetic ATF fluid in the transfer case. I don't know if the synthetic oil is better in the transfer case or not.

I replaced my front and rear differentials with AMSOIL Series 2000 75W-90, and AMSOIL Universal ATF in the transfer case.... been purring like a kitten ever since.

I have a 98 ml320 with 115k original miles. Is changing the diff oil a scheduled maintenance? If it is just good practice,when should it be done? Is it DIY or dealer item? Thanks.

__________________
87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)

My 98 only has 78,000 but I have always changed differential and T-Case fluid once a year in 4x4 vehicles. I do this because the axels get submerged in water from time to time and there is the chance they could get water mixed in with the oil. I do not think Mercedes has any reccomended change interval for them similar to the Transmission. I am not really afraid that the fluid is bad or is worn out. I am more concerned about contamination based on how I use my truck. Like Ron said I would not expect the fluid to look bad with only 78,000 miles. Also these are the only differentails I have ever worked on that had a drain any way. Most others you have to remove the cover to drain or siphon it out.