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Changing auto tranny fluid?


BobbyD
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By the time the trans has that many miles on it, it definitely needs it. The problem is, as they say, that the worn out parts that are now working OK with the accuumulated crap in there and fresh fluid lacking that grit may allow things to start slipping and not working the way it is now. That's how it goes...

 

They recommend changing the fluid every 30,000 miles, so the more often the better. People not doing it in the first place is the reason the trans wears out. Changing the fluid after it's been neglected is kind of a band-aid at this point. It's still going to wear out eventually, it just depends on trans temp and use/abuse when you drive.

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  • 3 weeks later...

Bobby,

I put your question to the auto trans specialist who I go to. He agrees with what 88 says i.e. if it has not been changed for a very long time the built-up crap covers all the seals, bearings, clutch and pressure plate packs and 'bands.

He did however say that if you leave it (don’t change fluid), then the wear will only get worse and that if the fluid is brown do something sooner rather than later.

 

He also mentioned that the fluid flush does not use ant solvents or detergents (or should not) as that would definitely move all the old crap and possibly make seals leak and clutch/bands more likely to slip. The fluid flush should be a quite gentle replacement of fluid by pumping it through and not a chemical or high pressure wash.

 

You could always just do a fluid change and see how it runs for the next few thousand miles and how quickly the fluid changes colour.

 

 

Geordie

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  • 3 weeks later...
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

To reiterate, when towing *anything*, the O/D OFF switch should be activated. Not only will this prevent the transmission from shifting into overdrive, it will also keep the torque converter locked up. Switching the E/AT transmission switch into POWER mode will not override the O/D OFF torque converter lockup.

 

You're friend may be right regarding the POWER mode in overdrive, but the combination of O/D OFF and POWER will keep the transmission much cooler than in AUTO mode (where it will shift more often and from a much lower RPM to a much higher RPM than in POWER mode).

 

I hope this makes sense. It's the only way to keep the transmission healthy, even though it's not mandated in the Owner's Manual...you have to piece the information together from the Automatic Transmission section and the Trailer Towing section.

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  • 1 month later...

I changed mine this weekend. What a horrible design I couldn't drop the pan because the tranny cross member and the exhaust cross over are in the way. So I ended up hacking the crossover and welding it back when I was done.

 

Is my truck the only one like this? That cross over pipe should be 2 inches closer to the front of the truck lots of room for it too.

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  • 4 weeks later...
don't most pathfinders actually have a drain plug for the tranny fluid? i might be on crack but i thought i remembered seein one on mine (shows much time i've spent underneath it since i got it a few months ago haha)

 

On my 91 pathy I have a drain plug and the cross member is not in the way.

I have been considering changing out the fluids and now I am positive and I am going to do it.

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  • 10 months later...
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.

 

Will it happen a lot, air bubbles coming in to the cooler ? And how long will it take b4 the cooler gets full of air ?

Than i better rotate mine.

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  • 2 months later...

Let me see if I'm hearing you guys right. Does the actual shifting of the tranny (say around town) cause more heat than leaving it in POWER mode and/or keeping the O/D off thus having higher revs from the engine?

 

I'll sacrifice a bit of fuel economy to baby the tranny.

 

Sometimes I'll leave the lever in "2" if I'm going very, very short distances from stop light to stop light. Engine only revs to about 2800rpms between them. My intension is to stop it shifting into 3rd gear and also giving me better engine breaking. I went from a manual to auto so I kinda like to play with the lever. Is this sufficient or should I leave it alone and just leave O/D off in the city?

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  • 2 weeks later...

Wait... so don't use the overdrive unless you're on the highway... or don't use the overdrive on the highway?

 

I'm confused... I thought O/D helped decrease strain on the tranny and improved fuel economy...

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  • 3 weeks later...

Regarding the O/D on the highway...

I don't know if Nissan was the only one smart enough... but if you switch the O/D off when you are going over (about) 55mph the torque converter will lock up (I'm pretty sure it won't lock unless it is O/D manually switched off). This is what would save the heat. It seems to give a pinch more power in my opinion - I use it to enter highways. You will feel it lock up around 55 and notice your RPMs drop just like when it locks in O/D. My Altima works the same. It's a very smart thing. I don't know much about converter locks, but why don't they just lock up in drive and stay locked? I know you can make a manual override - but are there some downsides to that? (another subject...) Oh, and how about this question... can you OVER-COOL a tranny? It can get down to -10F here on occasion.

 

I also found that if you set your cruse control for a speed less then you are going (i.e. 35 then go 55 manually) the converter will stay locked when you take your foot off the accelerator. This saves a bunch of lock/unlock cycling when you are on hilly roads and makes it feel easier to drive since it adds extra engine breaking. Just don't forget the cruse is still set for that lower speed!!! It'll kick in when you drop back down!

 

Regarding fluid changes...

I just recently changed mine (3rd owner, 184K, no idea of history). I was unsure about changing due to the "ain't broke" mentality, but figured it was a better option. I LOVE the fact that they put a very easy to access drain plug!!! The dealer said that there was no filter anyway, just a screen (I'm sure there is a magnet in there that's covered with gooey metallic junk...)

 

Rather than have a flush done for $120+, I drained the tranny, filled it with the exact same amount I drained (measured with wife's help [required begging]). I used MaxLife. It makes sense to use something designed for high mileage.

 

It took me about an hour and a half. I changed the fluid TWICE to be able to flush out a higher percentage of the old fluid (as everybody knows, the torque converter doesn't drain out). I drove about 20 minutes up to Wal-Mart to mix out the old fluid. It cost me about $40 and was very easy. The funnel that I bought was made for refilling. The plastic tube fit tightly into the dipstick/fill tube. Super easy.

 

Concern...

After the first flush the tranny made a funny sound, it also shifted smoother, which was good. It wasn't crazy loud, but quite noticeable. It scared me that I made the WRONG CHOICE!!! I can't explain the sound. It reminds me of a piece of very thin metal, like aluminum foil, dragging across a shaft very lightly. It wasn't related to gear selection. It made the sound in neutral when moving. It didn't increase in sound once you hit 25 or so.

 

I went ahead and did the second fluid change after I got back. This time the noise mostly went away. I still think I can hear it ever so lightly. Odd, eh? Ticking time bomb???

 

Finally...

I've put on at least another 3k (up to 188k) and it's been fine despite the faint noise, so far. It shifts better than it did before the change. However it has always shifted very hard, especially into 1st gear. Has anyone found any posts about that? (send link)

Edited by brickheadbs
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  • 2 months later...
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. ;)

 

This is a great thread!

 

On another forum, there were conversations about whether to run the external cooler with the original in-rad cooler at all or not. Other claim it is needed for daily winter driven vehciles.

 

If there is a design deficiency that leads the stock coolers to plug up, then perhaps using them is a bad idea. But if it just a matter of keeping them flushed with good maintenance, I wonder if using it is actually a desirable thing for those of who drive in the winter. The rad will be around operating temperature of the coolant of course - this could then ensure that the trans fluid does not run too cold in the winter cuasing sluggish shifting or whatever, especially if running an additional external cooler. Perhaps having a bypass for the external cooler only in the summer and both for the winter?

 

Just throwing this out there for ideas. I am not certain either way yet.

http://www.chevelles.com/forums/showthread...ighlight=cooler

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  • 6 months later...

I am running a 1995 Pathfinder LE with 35" tires and an A/T Transmission, I don't have a transmission cooler and I have been towing multiple vehicles behind it and I have never had any transmission problems but I do not drive with Overdrive on and I change the transmission fluid every 6 months regardless. She also has 312,000 kms on it.

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  • 2 months later...

I firmly believe that if you change the fluid as per the manual time frame, that it will be fine. The stock cooler is prone to clogging up, but my mechanic and another family friend (who is a mechanic/hydraulics engineer) say that it shouldn't clog up unless someone along the line, never changed the tranny fluid when they owned it. They also said it couldn't hurt, and recommend an external cooler AND filter if you tow a lot or run it on trails.

 

As far as my limited experience goes, the 93 has 340,000kms on it, with the original tranny and stock cooler. Still works great. No towing or wheeling ever. The 95 however had 220k when I got it, the fluid was brown, smelled burnt, and intermittently had no reverse. Clearly not maintained like my 93. I have had it flushed twice since, and I haven't had any further problems. When I removed the rad for the tbelt change, I flushed out the cooler just to be on the safe side, it was free flowing...

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  • 3 months later...

This post is great,

my transmission is original, and I have no idea of the maintenance before I got the truck. Until I started to learn more about mechanical stuff even my maintenance records were sketchy at best. However the transmission has been flushed several times during my ownership with no ill effect.

 

I just did my first transmission flush per 88's instructions on Sunday. It was by far the easiest thing I have done to my truck since I started doing my own oil changes. Also very satisfying to know you are saving 60 bucks.

No clunk now when I go from Park to Drive.

Edited by beastpath
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  • 7 months later...

With reference to fitting and aftermarket trans cooler, would it be better to put it on the leading surface of the radiator, and not the back, as air hitting the radiators front would be cooler than air that had already passed through a hot radiator. Also it makes sense to use some type of standoff bracket so there is a gap between trans cooler and radiator to stop heat transfer. Just ideas, may as well get the most out of the cooler as you can, and its not to much more difficult to install on the front than the back, maybe buying longer hoses.

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With reference to fitting and aftermarket trans cooler, would it be better to put it on the leading surface of the radiator, and not the back, as air hitting the radiators front would be cooler than air that had already passed through a hot radiator. Also it makes sense to use some type of standoff bracket so there is a gap between trans cooler and radiator to stop heat transfer. Just ideas, may as well get the most out of the cooler as you can, and its not to much more difficult to install on the front than the back, maybe buying longer hoses.

 

 

yep, you are right. In fact my instructions from my B&M cooler stated that for 100% efficiency it should be placed in front of the A/C condenser, for 80% efficiency between the A/C condenser and radiator, and for 50% efficiency behind the radiator. Most kits, if not all, come with pads you can stick on the cooler to separate it from the radiator also.

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  • 1 month later...

LOve this post! EXACTLY why I joined the forum. I needed a brand and B & M was mentioned so I guess I will go with that. Any suggestions for inline magnetic fluid filter for 95 Pathy? How large of a cooler would actually be necessary? Also, should I use ONLY original Nissan fluid? I am also looking for a brand for REMAN tranny if someone could help me with reputable brand/dealer....got 225k and want to get 500k!!! Thanks!

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  • 1 month later...

I just got my trans flushed and noticed something unusual. Before the flush, at a complete stop, the truck would start to quiver while still in drive. It still does it, but even worse now, so bad that I shift to neutral as I'm pulling up to a stop sign/light. First, is the quivering bad? and second, is it cool to shift to neutral, or will that hurt the trans? 124,000 on my '95 btw.

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