Should I change trans and diff fluid?

[USMC5811]

Hey guys, I have a 2007 M35x that I bought used with 60k on it and it just hit 100k so I'm trying to straighten out which maintenance I should do. I've already changed the plugs, PCV, air filter. My questions are below.

1. Is it important to change the trans fluid? I know most of you either change or flush your trans fluid every 30k miles, but I haven't had it done since i bought the car and as far as I know, it's not as necessary as people make it sound.

2. Should I change the diff fluid? Once again I know the answer is most likely yes, obviously it never hurts to change out fluids. I'm just trying to get a grasp on how big of a priority I should make it. Do i need to cancel plans and do it this weekend or can it wait a week or a month. Since it's AWD I know i'd have to do the front and rear.

3. When would you recommend having the belt replaced?

On a last note, last year I thought it would be funny to drive through big puddles during a rain storm because it bothered my GF. Well she got the last laugh because I caused a huge leak and the passenger side of the car got a ton of water in it because i blew out the A?C drain valve from the frame. Needless to say ever since then my A/C has a smell to it whenever it's hot out for the first burst of air. My guess is that it's either mold in the system, or just the smell of the stale air that comes off of my carpets now when they get hot. Does anyone have any suggestions on what I could do to remedy the situation that doesn't involve drilling a hole near my heater core?

Thanks for all your help guys!

[EniGmA1987]

Yes I would change both the trans and diff fluid. The diff can be done yourself with the right equipment (which is somewhat cheap and good to own) but the trans should be flushed at the dealer on the proper hardware. Once you do it, you can wait to do them again for somewhere between 30-50k miles.

[Frog]

Take a can or 2 of Lysol the brand that kills mold and mildew. Spray it directly where the air inlet is into the ac system. Both on recirculating and out side air. This will kill the mold growing on the ac exchanger.

[EniGmA1987]

As for belts, just keep an eye on them and do a quick look once a month. When they start to get any little cracks or start fraying then it is time to replace them. Maybe you dont need to do this check for 6-7 months after you replace the belts, but definitely do it once a month after having the belts on for the first year. I would say I have changed my belts about every 2 years on my car. I am almost due now, the belts are starting to discolor a bit. I might try out some Gates Racing belts this time rather than go OEM again.

[pedsemdoc]

1. Most people will say yes - current equipment does the right job. However, there are those that say a drain and fill is adequate (notice I didn't say optimal). I did my own drain and fill and the fluid was definitely dirty. I don't think I noticed any change in shifting, but it made sense to me that having little bits/dirt/detritus floating around in the fluid might not be so good for the transmission in the long run.

2. Ditto on the differential. Again, not a difficult DIY but can be a little messy, plus I have a RWD M45, so only had to do one vs 2 for the AWD.

3. Agree with EniGmA1987, you should check to see the integrity of the belts. if it(they) feel(s) loose with too little tension or you're squealing, prolly ought to change 'em. (not to difficult a DIY task, see How To & FAQ section)

4. There was a thread on the moldy/musty smell a few years back. Remember people suggesting Lysol vs Frigi fresh vs running your heater for a while after you've had the AC going and are almost ready to park.
You may want to check your in cabin air filter (look under the How To & FAQ section to see how easy this is to change) I had the problem pretty bad and noticed my in cabin filter probably hadn't been changed in a while, so I bought an aftermarket charcoal filter (cheaper than the OEM ones) and the problem has lessened quite a bit. I also change it a lot more regularly especially in the summer time when I'm running the AC more.

I think most of us would advocate a little preventative maintenance ends up being waaay cheaper than repair.

Good luck,

Craig

[USMC5811]

I'd like to thank everyone for the input. I will be changing my diff fluid within the next week or two and I'll also schedule a visit to the dealership for the trans fluid. I have to take my car in anyways for the recall so I'll get it all done in one shot.

Also thank you for the tip on how to get the musty smell out of my AC at first start up. I'll be trying the lysol idea soon as well.

[fat3oy]

My two cents:

Yes change trans fluid... Dealership charges a fortune, and you can do it yourself... A flush is not necessary... I moved to amsoil last year and have been fine, with a change, and running a bottle of fluid through the filler until it comes out clean in a steady stream. The only reason the dealership is preferred by non-wrench types is they take out, and replace the exact same amount of fluid, the flush is simply pressurized.

Yes change the diff... I went to amsoil on this as well... But only the rear is necessary... Get some gear lube, and a bottle pump and you are good to go. The front is not total all the time engagement... and even though I replaced mine with amsoil, it was not needed as the fluid inside was completely normal...

If your tension pulley maxes out... replace belt, thats it.

If your carpet was soaked use a steam cleaner... other than that you should be fine and having the typical AC smell we all deal with... I like FRAM's febreeze air filter in cabin... It has a chemical smell for the first couple of days... but jacks up any odors in the cabin for sure...

[psyopper]

As most have said, yes, change the diff and transmission fluids. Many manufacturers promise a "lifetime" fill of either or both of these as well as the power steering fluid, not sure about Nissan/Infinity. However, "Lifetime" usually means the manufacturers lifetime - the life of the warranty which often is much shorter than the actual life of the car.

Generally accepted maintenance practices are changing the transmission and differential fluid every 60,000 miles (100,000 Km). Unless your vehicle is acting abnormally you don't need to drop everything and do it right now. I'd say within +/- 5000 miles is perfectly acceptable on longer life fluids like these. Since the front diff is only engaged part time, and depending on your weather and driving conditions possibly less than 10% of the time, simply checking the front at 60K miles (the first interval) and changing it at 120K miles (the second interval) will suffice - as long as there's still some clarity in the fluid you should be fine.

In the past I would have done this work myself, but as I get older and have more stable income I find it's not as economically sensible to change these fluids myself. Also - if there's any sort of warranty on the car, either original or extended purchase, you are better off going to the dealership to make the change just to ensure your warranty remains valid. The two most likely times an AT fails are within 2000 miles of a fluid change (from dislodging gunk and dirt into the system) or it's catastrophic loss of life.

My local Infinity dealership charges $250 for transmission flush/fill service, and $85 for differential service, I don't find that to be an unreasonable price for either.