I have a 2002 land Rover Discovery, it uses 75w90 gear oil in both diffs and the t-case. I've been towing a fairly heavy trailer allot lately so I thought I'd change the gear oil and increase to a 75w140 oil. My previous gear oil, Lubro Moly 75w90, was only 21,000 miles old, however when I drained it out of the front and rear diffs, the rover diffs have an actual differential drain plug, it came out very, very black and had that lingering burnt smell. I didn't think anything of it, that's the way most gear oil smells when I drain it out. Kinda sad though for a high quality oil like Lubro Moly in only 21,000 miles.
Now for the part that confuses me. I drained the transfer case last, it's the hardest to deal with. The same Lubro Moly with the same miles came out of it as clear and clean as the day I put it in, and no burnt odor either.
The thing that gets me is that it is widely known in Land Rover circles that the transfer case, with a differential in it for the full time 4 wheel drive, is very hard on gear oil while the differentials are not that hard on oils at all. So my question is this, why would fairly fresh gear oil look and smell so bad coming out of the diffs? Why wouldn't the t-case be the same? Is there something inherent to differentials, or a previous, or ongoing maintenance condition, that would make the gear oil become so contaminated in such a relatively short period of time? The t-case seems to be free of whatever contaminating source plagues the differentials.
Also, the oil used prior to the Lubro Moly was Red Line 75w90, not the NS variety.
Thanks, Chris
Now for the part that confuses me. I drained the transfer case last, it's the hardest to deal with. The same Lubro Moly with the same miles came out of it as clear and clean as the day I put it in, and no burnt odor either.
The thing that gets me is that it is widely known in Land Rover circles that the transfer case, with a differential in it for the full time 4 wheel drive, is very hard on gear oil while the differentials are not that hard on oils at all. So my question is this, why would fairly fresh gear oil look and smell so bad coming out of the diffs? Why wouldn't the t-case be the same? Is there something inherent to differentials, or a previous, or ongoing maintenance condition, that would make the gear oil become so contaminated in such a relatively short period of time? The t-case seems to be free of whatever contaminating source plagues the differentials.
Also, the oil used prior to the Lubro Moly was Red Line 75w90, not the NS variety.
Thanks, Chris
