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ATF Cooler ‘87 Pathfinder

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Recently picked up an ‘87 pathy. Was told it needs the tranny serviced and possibly an ATF cooler. This is my first project vehicle on my own. I don’t have much background in mechaniking. Is this something that can be done by noob in an afternoon? My ex husband used to do all servicing of my former off road vehicle. On my own now. Scary, right? Please, be honest but not mean! Thank you!!

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I assume your truck has the auto trans. Basic service is to drain the trans fluid and refill with fresh. A more complete one would be to take it to a shop and have the trans flushed. The drain and fill replaces between 1/3 to 1/2  of the fluid and the flush does about 98%. The trans doesn't have a true filter so a filter change is not useful unless you have the pan off, which is not required unless it is leaking or repairs are needed. The transmission pan should have a drain plug in it for this service, much like changing the oil in the engine. 

 

The cooler is built into the bottom tank of the radiator. The original unit was a poor design that had clogging issues. If the radiator has been replaced sometime in the 30 years of your trucks life, it is likely to be ok. What many of us have done is install an aftermarket external cooler like the Hayden 1679 and just run the cooler hoses to it instead. I have gone this route with my 1993 Pathfinder. It is mounted between the radiator and air conditioner condenser, there was enough space for it to fit there. That does require removing the radiator to install the cooler there. 

 

With the trans fluid, it doesn't take anything special, your trans uses Dextron ATF, but a full synthetic version is better. 

 

If your transmission is having problems, it might be too late and might require a replacement or rebuild. 

 

Hope this helps. Feel free to ask anytime you have questions, somebody will be willing to help. 

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Mr_Reverse:

 

Thank you for the info. So far there are no issues with the transmission. It shifts smoothly. Just the nagging idiot light is on. Thanks again!!

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Light? Are you talking about the red A/T Temp light? If so, is it on all the time, or does it take a while. In the 21 years I have had and abused my Pathfinder, I think it might have turned on the light a couple times and I did burn up my trans once. Shop said they were amazed it came in under its own power and only had 3rd gear left. They even had to replace a planetary set in it. They showed it all to me when they got it torn down and it was ugly, I knew it was bad, but seeing the damage, I was impressed that it got there myself. I was also glad that I had decided to not do the rebuild myself, it would have been a bad time. It needed a lot of specialized work to fix it. 

 

I don't trust the Temp light and installed a gauge to keep an eye on things. 

 

It does sound like you might need to replace the radiator or bypass the cooler and run a big external one like mine if the temp light is turning on after a bit of driving. If it is on all the time, it might be a bad sensor or shorted wire. 

 

What part of the world are you in, what kind of terrain are you driving? Hot locations with a lot of steep climbs like the southwest is hard on the cooling systems and requires larger coolers with better airflow. 

Edited by Mr_Reverse

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I flushed mine myself using the cooler lines. Unhook, put them in a bucket, run the engine until it stops puking fluid, add the same amount of fluid via the dipstick tube, run again, repeat until the fluid coming out looks more like the fluid you're putting in. Mine was brown and had a little sparkle to it when I first disconnected the lines, which isn't a great sign, but not shocking on a truck with 200k+. I hooked it back up with an external cooler in line with the stock one (new-ish radiator so I'm not worried about it) and a Magnefine in-line filter to hopefully trap any remaining wear material. I used generic dex/merc ATF and ended up draining a little back out using the pan plug after adding about a quart too much (it can be tricky to get the level correct). I've never seen my AT temp light come on, +1 for checking wiring if it's on all the time.

 

I've got a paper copy of the '87 service manual, so let me know if you need specific info. Most things are similar to the later trucks, but there are a few curveballs in there, including the engine diagnostic codes (same procedure but they switched a few numbers around, just to be that way). Also IIRC the '87 was the only year that used a three-speed automatic, so if it does end up needing a trans at some point, you may be in for a scavenger hunt to find the parts you need.

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If it gets cold where you live, keep the stock cooler routed in line with the external trans cooler. I had issues with it not keeping the TC locked when it was 20 below. I've never had the light come on in the 15 years of wd21 ownership either.

 

I did the flush Slartibartfast did many times, it works well, just secure the hoses so they don't splash fluid all over.

 

Though I am glad to have a manual transmission version now. 

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