Trans Maintenance

[Scott-o]

Hi all -

We have a 2002 QX4 (four wheel drive version) that we bought a little over a year ago from the original owner. It has been great; we love it. It has about 165,000 miles on it.

I can't find in the records from the PO whether the trans fluid had been changed recently, so I want to do that this summer. It still looks OK, but I have a feeling based on the records that it has not been changed in a while.

What type of "service" will it need - does the trans have a filter in it; or just drain and refill the fluid? I don't think I'll do this myself, but is there anything I need to know about this service if I take it somewhere?

It is not clear in the manual how often the trans needs to be serviced, either. We don't put a lot of miles on it - we would be changing it based on time, vs. miles. How many years is it prudent to let it go between fluid changes?

Thanks in advance.

Scott

[MisterH]

You're correct - the FSM does not specify a fluid replacement interval. In the "old" days it was generally recommended to drain and replace ATF at 30-40k miles. Over the last 20 years most car manufacturers have migrated to a maintenance procedure just based on the mechanic checking and inspecting the condition of the fluid and determining if it warrants replacement. Some cars even have no provisions at all for draining and replacing ATF - they're sealed units. When you acquire an older vehicle and you do not have service records, it's a good idea to go ahead and drain and refill the ATF so that you have established a baseline of having known, good fluid to start with.

However, it's a good idea to get used to following the procedures for having a look at the dipstick level and seeing/smelling the condition of the fluid. Use a clean, preferably white rag to wipe the dipstick. If it's heavily tinged brown it means it's been overheating; possibly due to underfilling. If small, metallic particles are present then you have clutch material in it. If it's sort of a milky-pink you have engine coolant getting into the transmission via the radiator cooler lines. Those three conditions require fluid changing. It's really not a difficult service. You just need to get under the vehicle with enough clearance to drop the pan. There is a filter - actually more of a coarse screen that is mounted inside. It just needs to be cleaned with solvent. Since it's a really cheap part you could also just replace it too. Perhaps other members here will have thoughts about opting for additional filtering products.

[Blindaviator]

When I first picked up my Pathfinder I went to the trouble of dropping the pan and replacing the "filter" as that is what I was used to doing with my older cars. After seeing the "filter" is nothing but a gravel strainer and reading other posts here I learned doing all that was basically unnecessary.

You can save a lot of time and trouble and just drain the fluid and refill it. If it still looks dirty afterwards then drain and refill again. There is like a total of about 12 quarts of fluid in the system and draining only replaces about 4-5 with The remaining parts in the torque converter.

[atraudes]

Here is a link to the service intervals I use. The pan should have a drain plug, so dropping the pan shouldn't be necessary unless the gasket is asking to be replaced. On the other hand, dropping the pan after draining will let you see if there's any shavings or bits to be concerned about.

As for the internal filter, I wouldn't bother. Like MisterH and Blindaviator said, it's a rock catcher and is an absolute joke. I would, however, highly recommend installing a 5/16" fitting Magnefine filter. It should fit nicely in the rubber return hose coming from the radiator. It not only has a proper filter but a magnet inside. They're not terribly expensive and they're terrific insurance.

As far as replacing the fluid, you have two options. You can do a drain and fill a few times with a week or so between them, or a fluid exchange. The fluid exchange entails disconnecting a return line and pointing it at a bucket, starting the engine, waiting for 2 quarts to drain out, stop the engine, refill via the dipstick, and repeat until the fluid coming out is a fresh red color. The drain and fill is extremely straightforward and simple, but will likely cost a bit more and take more time overall. The fluid exchange is more of a pain but it's one operation and you're done, and provides better assurance that you've replaced all of the fluid.

The full steps for a fluid exchange can be found in the General Info thread, just look for the "How do I perform a transmission cooler line fluid exchange?" question. The procedure isn't specific to our cars, so you can also do a Google search for "transmission cooler line fluid exchange" and turn up plenty of other tutorials as well.

Lastly, you may want to consider changing the differential and transfer case fluids as well.

Hope that helps!

[Scott-o]

Great info, all. Good to know about the "filter" in the trans, because I was worried about that (ie "do I have to get that changed...").

I like the Magnefine idea, too.

And yes, I'm thinking the transfer case and diff fluid need changing as well. Because I don't see records of that, either. I have a fluid evacuator, I think I can just pull out the old fluid, and put in new. The trans seemed more daunting because of the filter, etc.

Thanks again,

Scott

[Blindaviator]

All three have drain plugs to make it easier. Transfer case is prolly the more difficult of the 3 as the filler plug was a little more difficult to reach compared to the diff filler plugs. You will have to use a pump and hose to get the fluid back in there.

Just make sure to remove the filler plugs BEFORE you drain the fluid. It would suck if you drained the fluid and then couldn't get the filler plug out for some reason.

[AlanAZ]

I've read that the diff drain and fill plugs are put in so tight at the factory that you basically have to destroy them to remove them. I bought new ones when I had my diff gear oil replaced (with syn 75w90.)

[Blindaviator]

I've read that the diff drain and fill plugs are put in so tight at the factory that you basically have to destroy them to remove them. I bought new ones when I had my diff gear oil replaced (with syn 75w90.)

They might just have thread locker on them??
I would try a little heat if they are too tight. Not so much heat that you ignite the oil inside though.

[atraudes]

Actually that reminds me of a few things I remembered while replacing my transfer case fluid. I highly recommend getting a proper square head socket set instead of just using the 3/8 end of your socket wrench. The size of your wrench head isn't quite right and you run a high risk of stripping the bolt. The 1/2 end of a socket wrench should be fine where applicable, though. The diff plugs shouldn't be too hard to get off, but the transfer case bolts are extremely tight. So, you'll also want a few breaker bars and/or pipe extensions. Having proper clearance is half the battle, so wheel ramps are a good idea. But, keep in mind the vehicle should be level when refilling.

And for the love of pete, make sure your vehicle is on something secure like jack stands. Any type of jack by itself isn't good enough. You will be pushing with quite a bit of force and the car could easily slip off a jack. I'm sure everyone here knows better, but it's better to overstate it.

[attofarad]

I don't find it necessary to lift the vehicle to do any of these fluids. I'll sometimes jack it at the end of the draining, to get a bit more out of the transmission by tilting, but I'm not under it when doing that.

[Densetsu]

Hint for the plugs: I just wrapped a few layers of electrical tape over the head of my breaker bar to get a snug fit in the plug. Didn't have any issues with maintenance on two Pathfinders with this method, beat buying a new socket or wrench just for this.

And for filling the diff and transfer case, I used this suction grease gun: http://www.canadiantire.ca/en/pdp/sucti ... p.html#srp

In case the link goes down, it's shaped like a grease gun but with a plunger on the back and a hose on the front. Fills a half-quart at a time. I let it drain overnight between doing the transfer case and the differentials so there was minimal mixing of ATF and gear oil, but it's probably not a big deal.

[rgk]

Regarding MisterH's post near the top of this thread, if your fluid has been contaminated with coolant or water and is milky-pink, that warrants a new transmission, not just fluid replacement.

That's because even a tablespoon of water in the trans will break down the wafer-like clutch material in no time.