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BobbyD

Changing auto tranny fluid?

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This is a question that has bothered me for years! With my Pathfinder and prior cars! Some people say,"oh yeah, you change your oil don't ya'"? Then others say, never ever change your tranny fluid. The pressure will be different with new fluid and it will screw with the tranny! What is the correct, if their is one, answer to this question?

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I've heard that in an auto tranny, if the fluid has not been changed regularily, and you decide to finally change it, it can have adverse affects. If, from new, you change the fluid at recommended intervals, it is definitely a good thing.

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I heard the same thing

 

reasoning is that the old fluid and grime may be holding seals that are worn out from leaking.

 

Tranny fluid contains a high amount of detergent which will wash out the grime and cause the bad seals to leak. Personally I'd rather find out I have bad seals.

 

I do regular tranny fluid changes on all my cars.

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Actually, ATF contains little, if any, detergents. It's usually the chemical flush that is used in some shops that cause the problems. I would just do drain and refills. Keeping that old, additive depleted fluid in there, is just going to kill you tranny quicker.

 

For the detergent in ATF:

http://theoildrop.server101.com/cgi/ultima...ic;f=5;t=002977

Edited by Steve_RI

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i say do it especially if the atf is not pinkish red, doesn't smell "sweet" and isn't viscous.

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DANGER!!!!!! DANGER!!!!!! DANGER!!!!!!

 

I'm on my THIRD automatic transmission, and have finally figured out how to make 'em last (@ $3,200+ a pop all said and done, I better have!).

 

1st, I FLUSH the transmission every 15,000 miles. This doesn't use detergent, but extra tranny fluid. Almost half of the old fluid is left in the torque converter upon tranny fluid draining, so there is A LOT of old, used, dark (ie non-lubricating) fluid left after a drain.

 

I buy 12 quarts of Red Line High Temp ATF, and take it down to my Nissan dealer. He puts it in his tranny flusher at the END of the flush, and runs it ALL IN to fill the tranny AND torque converter with ATF.

 

The killer of WD21 auto trans is HEAT, and the breakdown of tranny fluid due to that heat. You should do two other pro-active things to combat the heat problem.

 

1) Install a large (20,000+ GVRW) transmission cooler in front of the radiator. I run one inline with the factory cooler that is built into the Nissan radiator.

 

2) DO NOT use overdrive if you are

a) driving at 35 mph or less anywhere,

B) driving at 40 mph or less on a hilly road,

c) towing ANYTHING, no matter how fast you are going (this keeps the torque converter locked, lowering heat tremendously).

 

Also, if you must replace your AT, buy a remanufactured transmission, because they are built to a much higher standard than a new or rebuilt unit. Remans are available at your dealer or good transmission shops.

 

STOP THE LIES!!! :-) The tranny fluid will be very dark after 15,000 miles...DO NOT wait for 30,000 miles like the manual says. When I bought my first extended warranty for the Pathfinder, part of the requirements for warranty satisfaction were oil changes at 3000 miles and auto trans fluid changes at 15,000 miles. Boy was I suprised at how dark the fluid was after just 15,000 miles.

 

Sorry for the long post, but this is a matter near and dear to my heart. I've got well over 120,000 miles on my current tranny (after going through the first two at around 60,000 miles each).

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As Eli says CHANGE THE FLUID!!!! I just had mine flushed and the trans runs sooooooooo much better. A transmission cooler is also a very good idea something I have yet to do. However don't run it inline with the stock cooler, completely bypass the stock cooler. The problem with the stock cooler is that it is prone to clog. Stock cooler clogs, then there's no more fluid flow, and the tranny burns up quicker than a fireworks factory. And if the stock cooler clogs the external cooler does no good. This is something you should change Eli. ;)

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Not sure when the last time my Tranny fluid was flushed. I bought my Pathy with 67k miles and the owner prior to me was a Lease.

 

When I check the fluid it's a nice, very nice, reddish color. My mechanic says, if its not dark don't change it, if you have to change it... Wait for a dealer special and do it at the dealer and by ALL MEANS DON'T DO IT AT THE QUICK LUBE PLACES...

 

My Sienna which I have had from day 1 has got a tranny flush at 65k and another at 100k... Now at 101k and still purring like a kitten.

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You should change you transmission fluid on a regular basis, 10k to 15k is a good rule of thumb. I managed to have my first tranny last for 213K.

Be aware to check your belts as well when you change your tranny fluid. My second

transmission failed because a broken belt managed to sever the tranny cooling lines and

I was running dry before I realized what happened. Putting a tranny cooler is also an

exellent idea and bypass the stock cooler like SC88Pathy suggested.

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Alright people, I am convinced, like I always was, that tranny fluid must be changed! So when I bring my truck into my mechanic I should tell him to change the tranny fluid but leave what is in the converter? :help:

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if the converter doesn't have a drain plug (not sure on nissans, some other cars do) it's kind of a pita then.

 

definitely install the exernal cooler and by pass the stock one copletely. 15k? never seen it that dirty in any of my cars. i normally only change it when it looses the smell, color and/or slickness.

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How much is an external transmission cooler? And these Pathfinder have one that came stock?

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the stock one is part of the rad. look around on the forums. this topic (cooler) has been beat to a pulp.

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Alright people, I am convinced, like I always was, that tranny fluid must be changed! So when I bring my truck into my mechanic I should tell him to change the tranny fluid but leave what is in the converter? :help:

Sorry if I wasn't clear, but you should FLUSH the transmission every time. The WD21 V6 trans runs too hot to leave ANY used fluid in it.

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How much is an external transmission cooler? And these Pathfinder have one that came stock?

No stock EXTERNAL trans cooler from the factory. A good external trans cooler (such as Haydens or B&M) will run you under $100.

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Or $10 from a junkyard. I found that Ford Exploders have rather large external coolers right up front under their grille, easy to get to and cheap to boot. I run two of them in-between my radiator and the AC condenser. Here's a pic.

 

coolers1.jpg

 

DIY tranny flush: Do this with the engine/tranny cool, just in case.

 

1. Remove cooler lines from radiator and attach long hoses to the ends with hose clamps.

 

2. Using a clean bucket, place both lines in the bucket and have someone hold them there carefully.

 

3. Crank the engine over for a second(don't run it for long) and see which one shoots fluid out. Leave that one in the bucket and hold on to it for the next step.

 

4. Start the engine. Be careful, the output hose will be under rather high pressure and it may spray you if you're not holding onto it. The transmission's pump will now pump the old fluid out through the hose.

 

5. When the hose starts to sputter, shut off the engine. Using a funnel, pour new transmission fluid in through the fill tube. I'd say start with 6 quarts unless it really looks like you got less out of the trans so far.

 

6. Repeat Step 4.

 

7. Reconnect your cooler lines.

 

8. Check fluid level and adjust as necessary.

 

edited for content and accuracy! -88

 

That will change out nearly all the trans fluid without too much hassle. I've done it several times myself at home. It's exactly how the "Flush Machine" at Jiffy Lube works. I used to work at a Jiffy Lube as a pit man, and I never had a complaint about any vehicle afterward.

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Nice 88... :clap:

 

Me thinks to let this sit for a few days, then sticky it in the How To section, it should be VERY useful for many people...

 

B

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All good stuff...

One thing I would add - I found mounting my trans coolers with the outlet to the bottom (as shown on 88's) resulted in an air bubble catcher. Any little air bubble that entered the cooler rose to the top stayed in the cooler. Eventually, the cooler was pretty much full of air, greatly reducing it's effectiveness.

 

By rotating the coolers 90 (or 180) degrees so the outlet tube is at the top, they become self purging. The location of the inlet doesn't matter.

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What Eli Said.

 

My Dad Used to run a transmission shop and I worked as an RR man.

 

The number one killer of ATM's is HEAT!

 

The number two killer of ATM's is high water.

 

If you ford check your fluid. If it you see water change and flush. It is a sealed unit but the seals and gaskets can leak.

 

Put on the tranny cooler. Nothing worse than creeping a trail working the hell out of that tranny and the fluid id side by side with the hot water in your radiator fighting for air. A seperate tranny cooler helps prevent this. If the fluid is dark and has a burnt smell you have started to cook your clutches.

 

Feel the fluid, if you feel any grit the abrasive surfaces of the clutches have started to come off. Yes sometimes clean fluid makes it worse but it doesn't cause it, your transmission is gone and you are just waiting to get stuck on the side of the trail.

 

When you change your fluid if you do it yourself, look in the pan, usually there is a magnet that collects metal shavings. Clean it. If you see metal in the pan (take it outside and move it around to get the sunlight to show you any metal pieces.

 

Problem signs are burnt odor, dark fluid and metal in the pan.

 

Even if it's healthy change your fluid and flush the system every year or 30 thousand miles max! I would go lower. Tranny shops usually flush with parts solvent then clean fluid. yes it might show a seal to leak, again not caused by the solvent just exposed by it.

 

Good luck!

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The auto trans also has a breather hose located on the right rear (on mine). This rubber hose breather runs back to the cross member near the transfer case where it joins the transfer case breather and both join into a metal pipe that runs up inside the engine bay. I have extended mine higher and fitted a small filter to reduce dust intake.

 

I have seen these hoses pulled off by driving through sticks and bush so check that it is in good order. Also check the other breathers for the diffs (I think there are other posts about this).

 

I just had my auto trans serviced by a specialist and he also replaced the transfer case fluid with light gearbox oil (not with ATF) as he reckoned that it was better for the hard use I give the vehicle.

It just occurred to me that there is then a possibility for contamination of different oils from the auto breather to the T case via the joined breathers. Is that remotely possible?

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This thread motivated me to flush my fluid finally. Ive been putting it off for all of winter.

 

I should point out, the bucket method is only partially correct. The pump does not draw fluid in, it only expels it. Fluid must be added via the fill tube.

 

I also reoriented my cooler so the output was at the top. Thanks for the tip mws!

 

With the temperatures rising outside I am noticing more and more heat coming from the center above the tranny. The floorboard and console gets quite warm, and I can feel the heat coming up from the area. My cooler gets too hot to touch so I'm fairly certain it isn't clogged or anything.

 

Do others experience the same? Is this normal? Would it be advisable to add a second cooler? I'm currently running a Hayden 679, I believe rated for 30000lbs. I never tow anything so I dont see why this wouldn't be enough.

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So I should just take my Pathy to my local Nissan dealer and tell them to fully drain/flush my tranny and refill it?

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I have just had the auto trans flushed with clean fluid. It was a little brownish but the guy reckoned that this is OK for the last year’s 40,000km including a trip around Australia towing a camper trailer.

 

The flush was done by first draining and removing the pan, cleaning the filter, refit pan with a new gasket and refilling with new fluid. Then more new fluid was pumped in as the first stuff is pumped out through the cooler lines, with the motor running and selecting each gear during the process. This used about twice the quantity of fluid but put new fluid through all oil lines and the converter flushing all old stuff out without the box pumping dry at any stage.

 

The guy I took it to is an auto specialist who does a lot of work on 4x4's hot rods and drag cars. He had a few interesting comments regarding my Terrano auto trans.

 

1. he suggested moving or spacing the additional trans cooler out in front of the aircon radiator to space it further away and give it better cooling effect when it is hot weather and the aircon is working hard. Normal summer temp here is around 30C+ (100F) and it is normal to get well over 45C up north and inland.

 

2. he also suggested that I do ‘not’ use the "power setting switch" for longer than is absolutely needed particularly when towing. This setting (power) he said not only raises the revs at which change up occurs but also keeps the lockup in the converter unlocked for longer thereby producing more revs and more heat build-up.

 

3. it is also possible to fit a manual override switch to the torque converter lockup wiring so that it can be set to lock, unlock or normal position. He said that this takes a bit of effort $$ for the wiring to properly install with solenoids and diodes so that there is no risk of reverse voltage damaging or shorting out the electronic control of the trans.

 

Has anyone done this modification and is it worth the effort. Or are there drawbacks, risks.

 

Geordie

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I have just had the auto trans flushed with clean fluid. It was a little brownish but the guy reckoned that this is OK for the last year’s 40,000km including a trip around Australia towing a camper trailer.

 

The flush was done by first draining and removing the pan, cleaning the filter, refit pan with a new gasket and refilling with new fluid. Then more new fluid was pumped in as the first stuff is pumped out through the cooler lines, with the motor running and selecting each gear during the process. This used about twice the quantity of fluid but put new fluid through all oil lines and the converter flushing all old stuff out without the box pumping dry at any stage.

 

The guy I took it to is an auto specialist who does a lot of work on 4x4's hot rods and drag cars. He had a few interesting comments regarding my Terrano auto trans.

 

1. he suggested moving or spacing the additional trans cooler out in front of the aircon radiator to space it further away and give it better cooling effect when it is hot weather and the aircon is working hard. Normal summer temp here is around 30C+ (100F) and it is normal to get well over 45C up north and inland.

 

2. he also suggested that I do ‘not’ use the "power setting switch" for longer than is absolutely needed particularly when towing. This setting (power) he said not only raises the revs at which change up occurs but also keeps the lockup in the converter unlocked for longer thereby producing more revs and more heat build-up.

 

3. it is also possible to fit a manual override switch to the torque converter lockup wiring so that it can be set to lock, unlock or normal position. He said that this takes a bit of effort $$ for the wiring to properly install with solenoids and diodes so that there is no risk of reverse voltage damaging or shorting out the electronic control of the trans.

 

Has anyone done this modification and is it worth the effort. Or are there drawbacks, risks.

 

Geordie

I'm the guy who started this whole tranny post. Yesterday I wanted to take action on my tranny question by going to my local Nissan dealer to find out how much it would cost to flush my whole transmission system. The salesman there, a young 35ish year old guy told me(my pathy has 117,878 miles)that he would not recommend flushing the tranny at this stage because Nissan would not be responsible for the tranny shifting into different gears, leaking, etc,,,,,. He said that any dirt or sludge in there becomes part of the system! I am thinking of going to a 4x4 specialist. What do you folks think? :huh:

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