I'm about to change the fluid in my front diff and even though I know it's filled with 80w-90 from the factory, I was thinking of throwing some Mobil1 full synthetic 75w-90 in it because I remember reading elsewhere on here that the lighter weight gear oil reduces the "howling" noise that the diff makes when you let off the gas while driving in colder weather (it's 30 degrees here in Mass and my diff is noisy as hell!).

Any suggestions or objections to this before I do it? TIA!!

 

where in mass are you?

 

I'm staying at my folks' place in Norton, it's on the South Shore right off of 495...

 

That's exactly what I did about 7 or so years ago after reading a TSB in reference to transfer case failures due to the t-case's inability to overcome the dino 80w-90 in cold climates. I did recently find alot of metal in the fluid though during my last fluid change...pretty sure that the metal is from a carrier bearing. I highly doubt that changing to the syn fluid is the cause of the bearing failure though.

 

Did changing to the lighter weight oil help with the noise levels coming from your front diff? Was there a noticeable difference?

 

Honestly, I don't remember what it sounded like before, but it doesn't sound abnormal now when 4wd is engaged...I get some slight groaning on turns at times (in 4wd), but nothing louder than any other 4x4 front end that I've heard.

 

Ok, so I changed the fluid in my front diff out today and the "end" of the old fluid came dribbling out in more of a frothy, foamy, bubbley consistancy that has me a bit concerned. The drain plug only had a small amount of metal filings on the end and there were no "chunks" in the drain pan when I was done draining the old fluid. I pushed about a half quart of the new fluid through the diff to work the rest of the dirty, foamy fluid out just to be sure it was mostly gone before I put two fresh quarts of Mobil1 75w-90 synthetic in it. No signs of leaks anywhere either...

Should I be worried??

 

Now that you have fresh oil in there and you didn't see any significant metal shavings, no. The old fluid may have got some water in it somehow.

 

Sounds OK to me...

 

Cool, thanks for the feed back guys! I'm changing my transfer case fluid tomorrow morning and my rear diff later this week when my new Mag-Hytec diff cover shows up!