I wanted to start a new thread because the last one got pretty convoluted. There seem to be several different issues with whining manual transmissions and people are lumping them together. Here is the source of my issue and the fix:

05 G35 6MT with 33,000 miles - Since the weather has sucked, I took my G into the local Jiffy Lube to get the oil changed. They did their usual hard sell on additional services. I did my usual - don't even bother, until they mentioned that they would do the manual trans @ 50% off. I thought about the prospect of putting the car on jack stands and crawling under it in 20 degree weather, then told them to go ahead and change the MT fluid. Here is where things went bad: I asked them if they had a Mobile1 or other Sythetic substitute for the stock dino gear lube. The car had been shifting a little hard when cold, so i thought the synthetic would help improve this. The Manager did a bunch of research and came back and said they could do it.

Everything was fine for a couple of weeks. The weather warmed up and I hadn't driven the car much (less than 100 miles). Then we hit another cold snap. I started getting the symptoms that have been posted all over this board several times:

1. Very Rough shifting after sitting over night.
2. a faint whistling sound that sounded like an air leak - coming from the passenger side.
3. both symptoms went away within 5 minutes of the car being started.

The car was due for it's 30,000 service, so I took it into the dealer to have them check out the noise and poor shifting. They kept the car over night, told me the noise was "expected", then tried to sell me $1000 in other services. Instead, I went to the parts counter and bought 4 quarts of the the stock Nissan 75w-85 gear lube. Went home, drained out the synthetic and refilled with the Nissan lube. The hard shifting and the whistling noise disapeared.

To sum this all up:

• Replacing stock 75w-85 gear lube with synthetic resulted in hard shifting when cold and a faint whistling noise.
• Going back to the stock Nissan gear lube got rid of both issues.

When I drained the synthetic out I didn't see any signs of metal shavings or burnt lube. Hopefully, this had no long term effects on the transmission.

 

Wow--interesting.... Mine has actually been acting fine in our sub-zero weather. Last year it was whining a lot more. I didn't do anything to fix it...

 

I know this is an old thread but its the most recent one about cold weather shifting issues. Mine is notchy when cold (under 40), the solution with my Maxima was to use the Royal Purple manual transmission gear oil which really helped. I know the GM sycromesh stuff helps a lot of other transmissions too. Is there a consensus on which fluid to use to easy the notchiness? No unusual noises or anything like that.

 

OEM Nissan MTF or Redline MT85 are the most common recommendations. Redline MT90 is a bit thick and can cause notchy feel when cold. Nissan trannies need GL4 fluids, Mobil 1 is a GL5 fluid and the additives can damage the syncros over time.