At work, I became curious about my 2013 G37 sedan, which has about 184k miles. Since I got it at 163k, I wanted to do a transmission fluid change. I printed out the Carfax for it and saw that the transmission fluid had never been changed. Is it worth changing it now, or is it too late?

 

DO NOT change that transmission fluid, ever at this point. Keep it filled and check if to make sure it doesn't leak, but if it has not been changed the new fluid will almost certainly cause you problems. If you have a young transmission (60K or so miles?) then you could start proper fluid replacement and that would be preferred... but that ship has sailed.

Good luck,


Rick

 

I disagree. Our transmissions run hot and break the fluid down quickly. I believe a drain and fill which replaces roughly 1/3 of the fluid would not hurt anything and only improve the performance by replacing a portion of the broken down hydraulic fluid. I'd call a few transmission shops and local mechanics and get their take as well before making a decision based on information found on the internet.

 

You are free to disagree, no one paid for this advice.

You will find multiple posts here and elsewhere on this topic, and I have received the same advice from professional mechanics and from my race shop. When you have a 100K+ mile engine without fluid changes, the transmission has literally now worn in using this modified viscosity transmission fluid gradually over time. Any fluid changes will change the viscosity and potentially cause problems. If the transmission is acting properly and the fluid isn't thin as water and smelling like it's on fire, I would not change the fluid. Top it up as needed.

I have owned my G35 since new and G37 since it was young, and I maintain them with proper service intervals, so I am not in this case.

Good luck,


Rick

 

I have three kids of driving age and only buy high mileage quality used cars for them. On most, the transmission has never been services and there is slipping and suspiciously low mileage. I change the fluid and the car runs like new.

There are two sides to this argument, and the question is asked 10 times per week on the G37 sub. Personally, I would drain and fill as a full 10-12 quarts of fluid would likely raise the hydraulic pressure too much at once and marginal clutches may fail. That's the only science that makes sense for the never change your high mileage fluid or else approach.

 

What if I try to replace it and the fluid come out kind of dark should I drain it fully and fill it back up?

 

Draining through the drain plug will only yield 3-4 quarts (holds 9ish quarts). This is what we are referring to as a "Drain and Fill".

Refilling to the proper level is not trivial as the car needs to be running and a few cycles through the gears to make sure the fluid is being distributed inside the transmission.

 

I did a Transmission service with OEM fluid at my Infiniti dealer on my FX50 at 100,000 miles and I don’t think it had ever been done previously. I’m not exactly sure what they did - on the invoice they listed 10 quarts of transmission fluid but honesty I don’t know if they did a single drain and fill and just charged me for the 10 quarts or did something else like an actual flush. Didn’t ask.

At first, everything seemed good. Then at about 125,000 miles the transmission started acting funny. Between then and now I’ve done three additional drain and fills and each one made the transmission better to the point that it is practically normal now. The first one made the biggest difference and then the next two more of an incremental difference.

it made me wonder if that first service over time may have dissolved deposits, etc. that ended up causing problems. Upon three more drain and fills the problem was almost fully corrected.

Now I’m very paranoid about high mileage transmission services if your tranny is running fine. Just my two cents.

 

New fluid increases pressure, so it's valid to be concerned. Interesting that you had issues, but then those issues gradually decreased as subsequent drain and fills occurred. Wonder if that's just a coincidence? If the dealer charged you for 10 quarts, it may have been a fluid exchange service, but they normally note that on the invoice as it carries a $100-150 premium over a simple drain and fill. Mystery.

 

I’m very thankful that the next drain and fills fixed the issue 99%. I thought I was going to be out a Transmission and parts for an FX50 are VERY hard to come by. After the service at 100k I was getting some clunks and mechanical feeling issues. After the subsequent three drain and fills there was no longer any mechanical feeling of failure, but the tranny still seems to get a little confused in terms of what it wants to do at times, but doesn’t feel like anything mechanical. My guess would be something with the TCM or valve body rather than the transmission itself.