Beating a dead horse

[tommyabward]

I know this is asked all the time, but I'm just trying to find a definitive answer.

Took my 2003 QX4, that I just recently purchased, to a really reputable Nissan Infiniti shop here in SoCal for a transmission drain and fill. The truck just passed 85K. Unfortunately, I have virtually no record of prior maintenance or service on the transmission specifically from the previous owner... so I can only assume it's never been serviced. I'm probably foolish, but I liked it and the low mileage.

When I took it in for the change, shop advised me that if I swap the fluid I'd be asking for trouble. In his words specifically: "50/50 chance you'll have problems as a result." Something to the effect of "you're probably past the point of no return." I get the logic behind this philosophy, but I feel like leaving old fluid isn't really a plausible option either.

I casually asked this question on the forum, following another inquiry, a couple weeks ago. A few different members told me to change it, but every time I turn around I get a different answer.

What's the right way to go?

Thanks in advance.

[04pathse]

Well, based on what I have read on the subject, you should be fine with just a "drain and fill", a flush "could" cause problems at this point so I would not do a flush if I were you.

85k isn't too bad for a drain and fill but if you had 185k, then no it would be probably best to leave it alone...

[AZhitman]

The shop is prepping you for the 50/50 chance to soak you for more money.

Clean fluid is good fluid. Drain it, refill it, and don't go back there again.

[AlanAZ]

I was in the same situation, but with 120K miles. I have a truck with an unknown service history, but checking the AT fluid, it was a deep red color, and figured it had been changed, but all most overnight the fluid turned brown (no burnt smell, and still shifted well), and I knew then it hadn't, and I had to change all the fluid (and not leave half in the trans.)

I did a drain/fill/return line flush, changing all the fluid in one go (I'm also a big believer in keeping the additives package for oil/ATF the same, and since I wanted to move to a fluid designed for older transmissions -- Valvoline MaxLife -- that also meant changing all the fluid), did not remove the pan, but installed a Magnefine filter, which tests by Four Wheeler and Trailer Life show that it does reduce particulates well beyond an older design internal screen filter, and is much easier to change ongoing.

After taking an oil sample, we installed the Magnefine on the cooler return line and took the final oil samples at 2,269 miles. The initial sample was a very clean 15/12 ISO code, and we worried about seeing a noticeable change. Those very good numbers were due to the fresh oil and the SPX Filtran pan filter that was replaced at the oil change. Filtran uses MicroFelt media which delivers a better-than-average 80 microns nominal rating and would give you a small edge over the average "bargain" filters, many of which Filtran claims are 100- to 150-micron at best. Our fears about the Magnefine were unfounded. It dropped the ISO Code down to a squeaky-clean 12/9 by the end of testing.

One year and 10K mls later, fluid is a clear red color, trans shifts better than before, and I probably avoided a rebuild.

Clarification Edit: If you're going to do a simple drop and fill (changing half the fluid), then use the Nissan ATF, same as what is there now. Valvoline Maxlife would be appropriate if changing all fluid, or you had no idea what fluid was there now.

[yeldogt]

Doing a simple drain of the fluid from the drain plug is fine ... use the correct fluid ...Nissan D matic. If you are going to try and save $20 on the fluid purchase. .. leave it alone. I think the normal fluid change is 90k -- you want to refresh the additive pac. The transmission does not need any additional protection in normal use.

Lots of people with transmission problems -- get the fluid changed thinking that will fix a problem. Does changing the oil in an engine fix a bad crank bearing?... no. I has a relative who owned a transmission shop many years ago -- people would always come in with fresh fluid and dead transmissions .. The transmission was on it's way out prior to the change. People think changing the fluid will fix a failing transmission .. it will not,

Without going into all the variables -- transmissions and fluid are vastly different vs what they were 40 + years ago when these old wives tales came about.

The Nissan transmission is very robust -- lots of them make it to 200k. Both of mine made it well past 150k before I sold them ... and are still going with the people who bought them. Like anything else -- some fail earlier for a variety of reasons. Pulling a trailer is harder on a transmission -- even with an extra cooler and multi fluid changes.

[Qxx4]

just check the write up done on the forums and you do it your self without paying those people a penny

[tommyabward]

Thanks for the replies. I'll go ahead and change it.

So if we're talking just about the R50 ... where do you draw the line and just start saving for a rebuild or a new trans? What would that mileage figure look like, theoretically?

[AZhitman]

AT lifespans vary wildly. At this point, you don't know, since you don't know the service history or how it's been treated.

I'd set aside a $K regardless - I've seen them crap the bed at 95K and I know of many that have 200K.

(Another reason almost all of my vehicles have a manual trans).

[PalmerWMD]

I think the concern originated form a transflush machine. where you have an external pump pushing dirty fluid into the valves etc
A drain and refill is totally w/o risk and is the right thing to do.
Dirty fluid w/o its additives intact will continue to badly wear the transmission if its not refreshed.
A drain and fill replacing half the fluid goes along way towards that.

I just bought 2 used Nissan SUVs (a 2005 Xterra OffRoad a year ago and a 2012 Pathfinder Silver Edition a month ago both with 4x4 and 4.0L V6)

The Xterra only had 81 k on it.., Did a transmission flush.. needed a new valvebody 1000 miles later..... but luckily not a transmission rebuild.. so kinda doged a bullet there..
Still was it related to the flush? I do not know for certain.. but suddenly am leery of full transmission fluhes .

In all fairness I've owned many Nissans in last several years and new transmission fluid is one of the first things I usuaally did.... I until now always via a dealer flush machine.. and this was my first transmission problem with Nissan.

The Pathy got a drain and refill (at 102k.. in a 2012 that shows me a lot of hiway driving and the transmission fluid wasnt terrible so it had likely been serviced at least once in its life before).
Both vehicles are still in my possession and run great.

[tommyabward]

So after I do this first drain and fill, I'm guessing I should I plan to do it again a few months down the line since only a certain percentage of the fluid will be fresh?

[Hawairish]

A drain and refill is totally w/o risk and is the right thing to do.

Totally agree. I can't think of a valid reason to not do at least this. Unless you're filling it with wine instead of ATF, it ain't getting better with age. In addition to pressurized flushes, it wouldn't be surprising if some other failures were rooted by underfilling the transmission, seeing as it can be tedious to get fluid up unto the fill hole and inspect it properly.

So after I do this first drain and fill, I'm guessing I should I plan to do it again a few months down the line since only a certain percentage of the fluid will be fresh?

To some degree, sure, you will have old fluid and new fluid together, much like you would changing the motor oil. But in both cases, you'll replace much more fluid than what is left behind. In fact, I just did mine the other week, and it took almost as much ATF as I expected (i.e., what the FSM stated). I don't think the mixture warrants a follow-up drain, unless you suspect some other issue exists/persists, or if the initial drain reveals a questionable fluid quality. But, you can also check the fluid color on the dipstick, or even open the fill plug to check the quality of the fluid, without having to drain it.

[AZhitman]

^ Excellent advice from palmerwmd and Hawairish!

[yeldogt]

Just do it once. My guess you will find the fluid not all that bad. It's more important to use the correct fluid ... IMO ...never flush a transmission. Obviously, check the fluid level a few times in the week after to insure correct level.