So I changed out the transmission and differential fluids last week on my 04 MT. I used Nissan fluid for the transmission and Redline 75w90 for the diff. After the change I now smell gear fluid. I jacked the car up and checked for leaks and nothing. I used the recommended amount of fluids on both. At first I thought maybe the fluid that leaked down the side of the transmission/diff when I was filling it up might have been causing the smell but I cleaned everything down there pretty good. I also reopened the filler plug on both the trans/diffto let out any potential over fill and cleaned again but still getting the gear oil smell when I drive the car. Prior to the fluid change there was not smell at all. Any thoughts on this?

 

Gear oil has a pretty strong smell. If you don't have any evidence of leaks, then I would just clean the areas with brake clean and continue driving the vehicle. Note that both the 6MT and rear Diff have ventilation tubes at the top of each, it's possible the smell is just coming from there, in which case that would be normal, but you would need spidey like senses to notice (I never noticed a gear oil smell and I just serviced my 6MT). Make sure the vent tubes are secure/connected without cracks or leaks.
Cheers!
-Icer

 

thanks for your reply. Yea ive done plenty of gear oil changes and different cars and ive never experienced this before. I will take a look at the vent tubes next weekend.

 

Double check your rear axle boots and power steering rack/lines. It just occurred to me that this smell could be coming from somewhere else unrelated to the maintenance you just did. Axle grease and power steering fluid (ATF) also have a strong odor that could be confused for gear oil. Just trying to think of all possibilities since you say there's no leakage and you can smell it while driving. Also, when you get this smell, are you running the AC? Is it on recirculate or pulling fresh air from outside? Did you spill any gear oil in the car or track any in on your shoes/clothing?
-Icer

 

I highly doubt its power steering or axle boots but you never know. Im very familiar with gear oil smell. I can smell when i turn the air on pulling fresh air some times. I smell it more when im driving and I come to stop and ill get a whiff of it. As im driving I wont smell it much. I didnt track any to the inside of the car. In the morning when I get in the car there is no smell inside. Just weird as i had no issues before changing the fluids.

 

vicks vaporub under your nose when you drive.... bam problem solved

side note, when i was still a paramedic, we did this many of times when we had DRT (dead right there) calls where they had been there for a couple says

 

Im a nurse and we do that here at work when we have to care for some patients with infected wounds. Works great!