Weird auto trans problem w/ '95 Pathfinder

[MudSlug]

I have a 1995 Pathfinder LE 4WD. When I start it up, the automatic transmission starts in second and will not shift automatically. If I manually shift it with the gear selector, first gear is unavailable. However, once I get it rolling I can put it in neutral, turn the ignition off and then back on and it starts shifting perfectly normally, including first gear. I have to do this now every time I drive it. Turning it on & off while it is not moving does not make it shift correctly. It has to be rolling for that trick to work. Also, it will sometimes shift correctly on startup if it is really cold outside, but never on a warm or hot day.

 

I searched The Garage and found no thread describing this or similar transmission issues. Any idea what the heck is going on here? All help is appreciated.

[RCWD21]

Since you say turning power off and on again works I'd would think that it's something with the TCU (it's located in the back passenger side wall inline above the rear tire), it could also be failing solenoids or crud build up and with the cold fluid it's able to push past the blockage at a higher pressure than it would with hot fluid.

 

This is just speculation though but I would still check into the TCU and maybe even go to the junkyard and grab a spare and see if it makes a difference.

 

As long as it's from a wd21 platform it'll work.

 

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[LittleFR]

I'd do as stated. And line out anything electrical then do a trans filter and drive it a week and do a flush and fill.

[RCWD21]

I wouldn't worry too much about replacing the filter in the transmission itself, it's about as fine meshed as a screen door. Just do a few fluid changes with a good fluid and you'll be good to go. The only time you should really ever need to replace the filter is if it's physically damaged, and at that point you have bigger problems.

 

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[MudSlug]

Thanks, guys! I will try the TCU first, and then the solenoids if that does not solve it. Also, based on what I read on other auto trans threads here I will be adding a plate-style trans cooler and magnetic filter. I just moved to Texas from the PNW so heat will be an issue when the weather warms up.

[Citron]

I wouldn't worry too much about replacing the filter in the transmission itself, it's about as fine meshed as a screen door. Just do a few fluid changes with a good fluid and you'll be good to go. The only time you should really ever need to replace the filter is if it's physically damaged, and at that point you have bigger problems.

 

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You need to drop the pan anyway to change the fluid, for $15 why not change the filter?

[Cuong Nguyen]

You do not need to drop the pan to change the fluid it does help to see if you don't have large broken bits.

[RCWD21]

You do not need to drop the pan to change the fluid it does help to see if you don't have large broken bits.

+1..

 

The bolt head is either 17mm or 19mm. There's a crush washer on it to seal it to the pan. When you remove it be prepared to have a lot of fluid coming out as the RE4R01A holds a ton of it. I'd recommend at least a 3 gallon oil drain pan if you can get ahold of one. Also when refilling the transmission a transmission funnel makes things SO much easier and much less messy.

 

A Haynes manual or the FSM or even the 1500 page tech book just for this transmission will have the fluid capacity specs for either a total fill or a drain and refill. Make sure you know which amount you're putting in as over filling it isn't fun and could also cause some problmes.

 

Also here's the link to the solenoids incase anyone is interested, this is to the new solenoids, you'll see an option below to a listing for re-manufactured solenoids once you're on the website: http://www.oemsolenoids.com/copy-of-solenoid-set-re4r01a/

 

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Edited December 13, 2016 by RCWD21

[Citron]

Wow, someone actually made an auto tranny with a drain plug! I don't think I have ever worked on one with a plug. Does the torque converter also have a drain plug on these? On the auto's I am familiar with, to get all of the fluid out, you also need to drain the torque converter, it holds another few quarts.

[RCWD21]

Sadly these don't have a drain plug on the torque converter, that's why most people do a flush with cheap fluid and then drain and fill with a high quality fluid after a little while. I've read of someone (I think on here) that drilled and tapped a hole for a set screw so it could be drained but the only way to get to it is to remove the transmission inspection plates which are a PITA since you have to remove the starter, both engine to Trans braces, the front driveshaft and then wait and wait as the fluid drains through a tiny little hole, which as you can see isn't worth the hassle of going through when you can just drive with clean fluid for a little while then drain and fill with high quality fluid.

 

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[Terranovation]

I'm lucky with my Terrano that it has a drain plug and even a diesel tank drain plug. Why there's one for the gas tank I have no idea but it's there!

[RCWD21]

If I ever have to replace a fuel tank I'm having a drain bung added in before installing it just so if I ever get water or crud in my tank I can drain it and flush it out.

 

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[adamzan]

According to this thread it is just over 6 quarts but I think that is just a drain and fill. You can do a poor mans flush by taking the hoses off the cooler lines, putting them in a bucket, and then running the truck till it sputters, then refill and repeat. What I did was had my friend fill the fluid as it was pissing out of the line until we got fresh fluid all the time. This also changes the torque converter fluid. It is only messy if you let go of the hose, and it does use like 12 quarts of ATF.

[RCWD21]

According to this thread it is just over 6 quarts but I think that is just a drain and fill. You can do a poor mans flush by taking the hoses off the cooler lines, putting them in a bucket, and then running the truck till it sputters, then refill and repeat. What I did was had my friend fill the fluid as it was pissing out of the line until we got fresh fluid all the time. This also changes the torque converter fluid. It is only messy if you let go of the hose, and it does use like 12 quarts of ATF.

The only thing people need to be careful of is making sure that the hose that is in the fresh fluid stays submerged the whole time and that you shut the engine off before you run out of fluid in the bucket that way you don't starve the pump and possibly damage it or let the clutch packs run dry.

 

Other than that it'd be a good idea to keep the bucket of fresh fluid above the level of the transmission since it's only the return line from the pump.

 

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[Citron]

The only thing people need to be careful of is making sure that the hose that is in the fresh fluid stays submerged the whole time and that you shut the engine off before you run out of fluid in the bucket that way you don't starve the pump and possibly damage it or let the clutch packs run dry.

 

Other than that it'd be a good idea to keep the bucket of fresh fluid above the level of the transmission since it's only the return line from the pump.

 

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Agreed I thought the same thing about the pump.

[Slartibartfast]

I didn't put my return line in a bucket of fresh fluid and it doesn't sound like Adam did either. I think I jammed a spark plug in mine so it wouldn't drip on the floor. I spring-clamped the "out" line to an empty bucket, started the engine, let it run until old tranny fluid quit squirting out, then shut the engine off and poured fresh fluid in through the dipstick tube. The pump was only "dry" for the ten seconds or so it took me to walk around the door and turn the key. If you've opened a gear case, you know that even after you drain it, there's still a lot of oil clinging to things--evidently enough to sustain the internals for ten seconds of idling under no load. I repeated the process until I was out of fresh fluid, then plumbed the coolers back in. My trans still works fine. So does my friend's Blazer that got the same treatment. The only real difficulty on either job was getting the fluid level right afterwards. I guesstimated and ended up draining some out (gotta love that drain plug). On my friend's rig, we used quart jugs instead of a bucket, which gave us a pretty good indication of how much fluid to add. Just gotta keep track as you go.

 

Back to the OP's issue...

 

That's a weird one. While a fluid flush probably won't hurt, I would be very surprised if it fixed the problem on its own, and hesitant to put $50 worth of fluid in it until I was sure I wouldn't be draining it out again to service something inside. I am of course assuming that the fluid's at the proper level and that it's not black with chunks in it. Maybe a check valve or something is sticking and flushing some gunk out would free it up... but this sounds electrical to me. The TCU locks into second when it thinks there's something wrong, and if you check out the AT section of the service manual, there's a procedure to read what the TCU thinks is wrong from the flashing light in the E-AT switch. I would start there. If that tells you nothing, or what it tells you doesn't help, then yeah, I think I'd be looking at the TCU next.

[RCWD21]

I didn't put my return line in a bucket of fresh fluid and it doesn't sound like Adam did either. I think I jammed a spark plug in mine so it wouldn't drip on the floor. I spring-clamped the "out" line to an empty bucket, started the engine, let it run until old tranny fluid quit squirting out, then shut the engine off and poured fresh fluid in through the dipstick tube. The pump was only "dry" for the ten seconds or so it took me to walk around the door and turn the key. If you've opened a gear case, you know that even after you drain it, there's still a lot of oil clinging to things--evidently enough to sustain the internals for ten seconds of idling under no load. I repeated the process until I was out of fresh fluid, then plumbed the coolers back in. My trans still works fine. So does my friend's Blazer that got the same treatment. The only real difficulty on either job was getting the fluid level right afterwards. I guesstimated and ended up draining some out (gotta love that drain plug). On my friend's rig, we used quart jugs instead of a bucket, which gave us a pretty good indication of how much fluid to add. Just gotta keep track as you go.

 

Back to the OP's issue...

 

That's a weird one. While a fluid flush probably won't hurt, I would be very surprised if it fixed the problem on its own, and hesitant to put $50 worth of fluid in it until I was sure I wouldn't be draining it out again to service something inside. I am of course assuming that the fluid's at the proper level and that it's not black with chunks in it. Maybe a check valve or something is sticking and flushing some gunk out would free it up... but this sounds electrical to me. The TCU locks into second when it thinks there's something wrong, and if you check out the AT section of the service manual, there's a procedure to read what the TCU thinks is wrong from the flashing light in the E-AT switch. I would start there. If that tells you nothing, or what it tells you doesn't help, then yeah, I think I'd be looking at the TCU next.

I just mentioned that incase someone reads this and then does the flush and let's it run for a few minutes. I'd say 10 or so seconds would be ok since there is still a coating oil atf on everything but for someone to let it keep going is asking for trouble.

 

But back to the OP'S post, sorry for the bit of a thread jack!

 

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[adamzan]

I didn't put my return line in a bucket of fresh fluid and it doesn't sound like Adam did either. I think I jammed a spark plug in mine so it wouldn't drip on the floor. I spring-clamped the "out" line to an empty bucket, started the engine, let it run until old tranny fluid quit squirting out, then shut the engine off and poured fresh fluid in through the dipstick tube. The pump was only "dry" for the ten seconds or so it took me to walk around the door and turn the key. If you've opened a gear case, you know that even after you drain it, there's still a lot of oil clinging to things--evidently enough to sustain the internals for ten seconds of idling under no load. I repeated the process until I was out of fresh fluid, then plumbed the coolers back in. My trans still works fine. So does my friend's Blazer that got the same treatment. The only real difficulty on either job was getting the fluid level right afterwards. I guesstimated and ended up draining some out (gotta love that drain plug). On my friend's rig, we used quart jugs instead of a bucket, which gave us a pretty good indication of how much fluid to add. Just gotta keep track as you go.

 

Back to the OP's issue...

 

That's a weird one. While a fluid flush probably won't hurt, I would be very surprised if it fixed the problem on its own, and hesitant to put $50 worth of fluid in it until I was sure I wouldn't be draining it out again to service something inside. I am of course assuming that the fluid's at the proper level and that it's not black with chunks in it. Maybe a check valve or something is sticking and flushing some gunk out would free it up... but this sounds electrical to me. The TCU locks into second when it thinks there's something wrong, and if you check out the AT section of the service manual, there's a procedure to read what the TCU thinks is wrong from the flashing light in the E-AT switch. I would start there. If that tells you nothing, or what it tells you doesn't help, then yeah, I think I'd be looking at the TCU next.

Yeah I definitely didn't leave it in a jug of ATF. I wonder if it would suck it in and flush itself? Regardless, that original trans ran fine for 6 more years until I sold the truck to my friend for his farm as it was rotted to fskc.

[Slartibartfast]

I'd be surprised if the return sucked anything in, unless maybe if the trans breather was clogged. AFAIK it just dumps into the pan.

[RCWD21]

If I remember correctly I believe it does just dump back into the housing somewhere about mid level, all I know is that there's a ton of passages in these autos that get clogged up when clutch packs get overheated and decide to break apart along with destroying the brake band.. took me nearly a week to clean everything out and to make sure it was clear.

 

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[adamzan]

OP: If the fluid change doesn't help, and it passes all the checks on the self test (see the FSM), then I would look for a new/used trans. You could also check to make sure there are no speed sensor related codes in the ecu, as it will cause issues with the tranny.

 

I think 100% of the issues on these transmissions is due to lack of maintenance. My dad had a 93 wd21 from 96 till 2006 and never had any issues, changed all fluids at Nissan recommended intervals, and it lasted over 400,000 before succumbing to rust.

Edited December 21, 2016 by adamzan