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Changing auto tranny fluid?


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#1 OFFLINE   BobbyD

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Posted 27 April 2006 - 04:09 AM

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?

#2 OFFLINE   Simon

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Posted 27 April 2006 - 04:15 AM

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.

#3 OFFLINE   Gotrek

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Posted 27 April 2006 - 05:26 AM

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.

#4 OFFLINE   Steve_RI

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Posted 27 April 2006 - 05:39 AM

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.se...ic;f=5;t=002977

Edited by Steve_RI, 27 April 2006 - 06:01 AM.


#5 OFFLINE   94extreme

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Posted 27 April 2006 - 10:30 AM

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

#6 OFFLINE   Eli

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Posted 27 April 2006 - 11:30 AM

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).

#7 OFFLINE   SC88Pathy

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Posted 27 April 2006 - 11:41 AM

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. ;)

#8 OFFLINE   rmd0311

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Posted 27 April 2006 - 11:44 AM

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.

#9 OFFLINE   v6engine

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Posted 27 April 2006 - 06:46 PM

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.

#10 OFFLINE   BobbyD

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Posted 28 April 2006 - 07:03 AM

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:

#11 OFFLINE   94extreme

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Posted 28 April 2006 - 08:48 AM

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.

#12 OFFLINE   BobbyD

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Posted 28 April 2006 - 10:53 AM

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

#13 OFFLINE   94extreme

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Posted 28 April 2006 - 11:10 AM

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

#14 OFFLINE   Eli

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Posted 28 April 2006 - 04:16 PM

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.

#15 OFFLINE   Eli

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Posted 28 April 2006 - 04:17 PM

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.

#16 OFFLINE   88pathoffroad

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Posted 28 April 2006 - 04:59 PM

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.

Posted Image

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.

#17 OFFLINE   Precise1

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Posted 29 April 2006 - 10:31 AM

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

#18 OFFLINE   mws

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Posted 03 May 2006 - 03:03 PM

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.

#19 OFFLINE   Pathylogical

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Posted 04 May 2006 - 04:35 AM

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!

#20 OFFLINE   geordie4x4

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Posted 12 May 2006 - 08:27 AM

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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