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Story goes as follows : I found a 1 owner 2000 Frontier crew cab 4wd with a good host of options , 280,000 miles and in pretty decent condition inside and out for sale and i wanted it , guy said the engine was replaced by the Nissan dealer at just over 100,000 miles when it self destructed (probably timing belt broke) and most all of the miles were highway miles as he drove a lot for his job ,, that`s how it started ,, well it had an issue he was up front with about the trans not having reverse , went out after thanksgiving of 2018 but they were driving it anyway , just not parking where they had to back out of . So i go check it out and it starts right up runs good , took it for a drive and verified the reverse did not engage like he said but it drove good , had a little play in the steering and a small oil leak from the back of the engine and some other minor issues but basically he wanted it gone and i got it for a steal and he even threw in the original window sticker as a bonus !! Well i get it home and park it till i decide what to do with it , found a transmission at my local pick and pull from another 2000 model crew cab that was a flood vehicle and was low mileage , got the trans and transfer case with it for $250 , meanwhile i pulled the battery out as i wanted to go through and replace the timing belt /water pump /gaskets and a few other things on the motor before i started working on the trans , so got through working on the motor , put the batt back in and started it up , as it was sitting there running i went to put it in drive to move it and as it went from park to reverse ,,, Reverse worked !!! It engaged and moved back like nothing was wrong , went to drive and back to reverse and it worked every time ,,,,, until ,,,, i shut it off and went in for supper and came back out to take it around the block and reverse isn't working any more , no check engine light or codes showing on my basic code scanner ,, so what i want to know is what was going on , is it fixable as is and just needs new soleniods or something ?? That`s where im having trouble understanding , i have googled for info but im not finding anything helpful ,,
 

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Somewhat of an update , i finally got around to figuring out how to pul the tcu trouble codes and all i got was a constant flashing of the o/d light which indicated a problem wth the tcu or short somewhere in the wiring i read online , i repeated test a few more times to confirm i done it right and got same result each time ,,, decided to drop the pan and check the solenoids and wiring but when i got under the truck and poked around with the wireing on the trans i saw a connecter that was unplugged and looked to be tucked into the wire holding bracket then i found the other end further up the harness , it`s the one that went to the sensor at the tailshaft end of transfercase , plugged it back up and checked the tcu again for codes and this time it worked showing normal no faults , 1 long flash followed by 10 equally spaced on and off flashes and then loops back to repeat the same sequence , so ok it means good tcu and wireing connections at this point ,,, i drained the fluid which looked exactly like motor oil and drop the pan and to my surprise i found absoulutly nothing out of the ordinary in the pan , no clutch lineing pieces no broken metal or plastic parts nothing in or blocking the filter , just some metal "mud" sticking to the magnet with no chunks in it , and the valve body and internals that i could see looked like brand new ! i ohmed the solenoids and they checked out good so i replaced the filter and gasket with new and put everything back together , just waiting on the weather to get back outside to refill with fresh fluid and try it again and see what happens ,,, so at this point i can only guess that it has either a pump failing or torque converter failing or both at this point ,, with no way of being able to check line pressure at idle and stall speeds i can only guess at this point
 

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Trying to give updates here with what i found out so far , dont know what happend to my last post here but looks like my trans may have a pump issue , so im going to be pulling it and swapping in the other one i have on hand .
 

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Could be a pump. Sometimes the input shaft teeth will strip in the torque converter. However, in either of these situations, you will usually lose forward gears as well as reverse. Before you pull your old trans, you should hook up an oil gauge (or transmission gauges) and measure the pump pressure, as that would tell you if the pump is good or not before you potentially waste time and effort replacing it. A more common occurrence in no reverse gear problems (but forward gears are good) in automatic transmissions, including the RE4R01A Jatco transmission, is that the snap ring in the reverse clutch drum will pop out of it's groove inside the drum. When this happens, the reverse clutch drum piston can compress the friction and steel plates inside the drum, thus, no reverse gear. Unfortunately, the repair for this is to R&R the transmission and tear it down to replace the reverse clutch drum assembly, or, at least the drum and snap ring.
 

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Hey thanks for replying ! I would like to do a pressure check but i dont have the gauges , i had pulled the pan expecting to see a bunch of shavings and clutch material but i was surprised to see it was clean and that there was only a metallic build up on the magnet in the shape of a flower . I ohmed out all the soleniods and found them to be with in the spec`s that i found in a service manual online so i just put it back together with a new filter and gasket and fluids and tried it again , i got the same results but it sounds and feels like it tries to go in reverse but it doesent , it makes a soft sounding metallic clank noise and then it buzzes then it goes silent , it also delays going into drive but engages immediatly just about everytime when i go straight to 1 on the shifter ,, so i figure if it has to come out anyways i might as well put in the one i have on hand and pray it works and then take the time to tear down the one i pulled out and go through it and see what was going on then order needed parts and learn how to rebuild it for a spare ::smile::
 

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I believe Autozone has transmission pressure gauges, or at least on oil pressure gauge, available in their tool loaner program.
 

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I was there today and checked but they dont have anything like what im needing , i am thinking about a gauge kit i seen from amazon , OTC Tools 5610 Trans-Eng Oil Press Tester , made specifically for transmission pressures with a 400 psi guage and for engine oil pressures with a 100 psi guage , but i wont be able to get it before i change out my transmission to check it with ,,,
 

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I would think if you have a pump/pressure problem, it would show up in the forward gears also. It sounds to me it could be a linkage problem … have you tried moving the linkage s-l-o-w-l-y through the range and see if reverse engages somewhere in between selector positions. I'd also try disconnecting the battery again, just to see if that works again?? Just a thought …. :)

(on a side note … wow, that truck looks CLEAN underneath !!! )
 

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I would think if you have a pump/pressure problem, it would show up in the forward gears also. It sounds to me it could be a linkage problem … have you tried moving the linkage s-l-o-w-l-y through the range and see if reverse engages somewhere in between selector positions. I'd also try disconnecting the battery again, just to see if that works again?? Just a thought …. :)

(on a side note … wow, that truck looks CLEAN underneath !!! )
Line pressure runs much higher for reverse gear (about 100 psi idle/212 psi stall) than forward gears (about 65 psi idle/155 psi stall), so it's possible to have low pump pressure, enough to not engage reverse, but still have enough pressure to operate forward gears. This is why it's important to test pressure with a pressure gauge. If it's a case where the input shaft has stripped the teeth in the torque converter, then it will affect both forward and reverse as pump pressure will be at or near 0 psi. It is a good idea to check the linkage as you suggested, as shifter bushings due fail due to heat and dry rot over time; it is one of a number of checks that need to be made when trying to diagnose a transmission problem.
 

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I was there today and checked but they dont have anything like what im needing , i am thinking about a gauge kit i seen from amazon , OTC Tools 5610 Trans-Eng Oil Press Tester , made specifically for transmission pressures with a 400 psi guage and for engine oil pressures with a 100 psi guage , but i wont be able to get it before i change out my transmission to check it with ,,,
Hi Cloudy,
Were you ever able to pull apart the original transmission to find the source of the problem?

Thanks
 

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Discussion Starter #11
I havent torn it down yet but when i got it out and on the ground i pulled the torque converter off and found the "ears ?" on the hub that mates with the pump to be chewed up pretty good , i have pic`s and when i get the chance i`ll post them later on today hopefully ,, so basicaly pressure loss is what killed this transmission ,,, from what iv`e been able to find is the way the pump builds and maintains pressure is not an ideal design and leads to a pressure spring weakening and a decline of pressure across the board and then , well you know the rest ,,, also it didnt help that the previous owner continued to drive it untill total failure occured ,,, but overall it looks like it`s going to need a new torque converter as well as a pump assembly if they are still availible and a rebuild kit ,, and hopefully that should do it and i`ll have a good rebuilt spare when i need it again !
 

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here`s one i found of the torque converter , i thought i had more but i cant seem to find them
312641
 

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Discussion Starter #13
oh, even though i didnt have a pic , the converter from the replacement trans had no wear on it like the pic above !
 

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Thank you for the information, it is very helpful. I have a 2004 Xterra with a no reverse problem (No Reverse in 2004 4x4 SC). I knew almost nothing about automatic transmissions before last weekend when the problem started but I have read a lot. I've been suspecting a hydraulic problem rather than a friction/clutch problem though I was hoping it was something I could fix without dropping the transmission (I don't think I can do it myself). I have a pressure gauge coming this week that could confirm our suspicions.

Another thread with a problem just like mine (2002 2WD XE V6 - No Reverse) attempted a valve assembly cleaning and solenoid replacement that didn't resolve the problem. Later, during a rebuild, his mechanic found the problem:
It turns out that my reverse issue is due to a part that is apparently related to the pump, if I understand correctly from my mechanic. He said the part is called a "stator" and something is wrong with it. I guess it's partially worn out or something.
I don't know what he refers to as "stator" as that is usually something (also called rotor) inside the torque converter that allows torque multiplication. The oil pump has a rotor, maybe the mechanic or thread author confused it for stator.

In your photo, I see the damage on the machined flat of the torque converter drive hub which, I believe, interlocks directly with the rotor of the oil pump and provides engine speed to the oil pump. Tell me if you disagree; however, I don't think that the problem comes from the TC drive hub slipping inside the oil pump rotor. It seems there would be much greater damage and loud symptoms if that was the case. Maybe the rotor is damaged (a vane might have broken) and temporarily jammed the pump rotor causing this damage to the TC hub that was driving it.

You mention a pressure spring weakening, do you have more information on that (which/where)?

A damaged rotor causing decreased pressure correlates with the symptoms as smj999smj mentioned in post #9 above. Also, when the oil is cold and more viscous, the reverse clutch may be more likely to engage under this low pressure which is something we've seen. I'm going to try an additive after testing the pressure, this may improve clutch friction under lower pressures.

I'm still hoping for a fix that doesn't involve pulling the transmission or alternatively, I'd like to narrow this down so I know if I'll also have to purchase a torque converter and/or parts of the oil pump if I have it rebuilt.

Thanks again. Any more information and opinions are always appreciated.
 

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Discussion Starter #16
In the diagram above ; the control piston and the cam ring spring are the issue points of wear in the pump assembly and what is usually the cause of pressure loss , generally speaking , in a nutshell what happens is the cam ring spring looses tension or breaks and causes the control piston to flutter and wear faster to where it wears a groove in it`s "seat" and it there by allows a pressure loss ,,,, is as best as i can describe it at this time ,, ( i`m currently in the middle of studying for a chemistry & electrical test and glad for this little break away to help someone out , lol ! )
 

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Oh , forgot to add , i changed the trans out by myself in my driveway under the carport over the course of several days and have the pic`s to prove it !! I`ll not do it again if i can help it ,, lol !!!
 

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Interesting, the control piston. I've wondered what it does and how it works since I first saw it. Maybe it has something to do with the feedback pressure? Concerning the pressure loss problem with the piston wearing a groove, where did you learn about this? Do you have a link? I'm wondering if it is rebuilt, what might need to be replaced in the pump (if not all of it). Don't worry about it if you've compiled all that from many places; I don't want to distract you from your studies.

As a side note, I was surprised to see that the oil pump has lines for the high clutch, torque converter (release/apply) and the reverse clutch. I thought there would just be one pressure line going to the valve body where the solenoids would decide where to send the pressure. I'm not sure why it is built like this.

Thanks, this is all really helpful and I'm sure would be helpful to others that have the same issue as we; I'm linking this thread from my ClubXterra thread. Good luck on the exams.
 

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Some more things are coming together. In the oil pump, the rotor and vanes spin inside the cam ring but are offset, they are not coaxial; this provides the pumping action. The cam ring is held in position by a cam spring. The cam ring also actuates with the control piston. I just watched a video (Youtube: How Rotary Vane Pumps Work (Engineering)) regarding a generic rotary vane pump and the narrator called the cam ring a stator (it is stationary). That must be what the mechanic was referring to!

The video also discusses "variable displacement" where if the center of the cam ring is moved closer to the center of the rotor, the pumping pressure is decreased. In our RE4R01a transmissions, I'm going to guess that when the oil pressure is too high, it pushes on the control piston which displaces the cam ring (against its spring) so its center is closer to the rotor center; it then pumps less forcefully. If the cam spring has weakened or if the control piston doesn't move back when the pressure decreases (grooves), then the cam ring will permanently or too easily be displaced so its center aligns more closely with the center of the rotor and you will have decreased oil pressure.

This seems very plausible given what we have seen/read. I'm still interested in a link that you might have which talks about the spring, piston and grooves.

If I can be more sure that this is the cause, I'd like to investigate a way to resolve the issue without pulling the transmission. If the spring is weak, maybe via the control valve body, the return flow can be restricted so as not to put so much pressure on the control piston and cam spring allowing them to rebound and cause more pumping pressure. Tapping an adjustable screw into the proper line might do it.

I know very little about these things and would love to hear anyone's opinions.
 

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RE4RO1A Teardown - YouTube ,, at around the 36 minute mark he starts tearing into the pump assembly and then at the 38 :25 mark he starts discussing the issue with what he calls the actuater but it`s what the fsm call`s the control piston ,, watch the vid and see what you think , and then there was this old link i found too from 2016 that touched on the subject Jatco RE4R01A 4speed automatic info ,, i may have another link somewhere but this is all i can find at the moment that i have saved on the topic ,,
 
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