Joined
·
39 Posts
I thought I would start this thread here to document some technical details and issues regarding the automatic transmission found in the 2005+ Nissan Frontiers, with specifically the 4.0L V6 engine.
I have learned all of this because I have been researching and troubleshooting my own transmission in my 2006 Crew Cab V6 4x4 Frontier SE with 175k miles.
Basic Information:
The automatic transmission (both 2wd and 4wd) is officially called an RE5R05A. It is a 5-speed automatic transmission. Gear ratios will vary by application. This same transmission (in slightly different forms) is used in many other Nissans/Infiniti models and other makes/models as well.
Issues:
It is safe to say that most of the issues with these transmissions (as used in the Frontiers/Xterras) can be traced back to two innocent looking hoses connected to the lower tank on the radiator. The radiator can fail and cause cross-contamination of engine coolant and ATF. This means that you will get a milky sludge in your transmission. NOT GOOD.
Many people (and the service manual) call this connection to the radiator a "trans cooler". However, I do not think that is 100% accurate. I believe the only purpose of this mechanism is to accelerate the warm-up of the ATF for better cold-start driveability. The Frontiers for sure (and probably Xterras too) already have an OEM ATF air-cooled heat exchanger located behind the grille, in front of the radiator. You can easily check your own vehicle by peering through the grill on the passenger side of the Nissan emblem.
Here is description of it from the service manual.
![]()
On my vehicle I have chosen to bypass the radiator. So all cooling is done with the air cooled one. In my climate and driving, I don’t have any need for extra cooling that could come from the ATF routing through the radiator. Your application may be different.
When I purchased the truck, the previous owner had said they just got the radiator replaced. I didn’t think much of it at the time, but it did have a shiny new radiator in it.
My Issue:
I have been experiencing SES lights on my dashboard. Scanning the OBDII port has pointed to P0850 “Park/Neutral position switch circuit” (PNP switch). I had no drivability issues, so I would just reset the code and continue on. It would be fine for a week or two, then the light would come back on. Did this for a couple months until one morning after resetting the code, the transmission went into limp mode (feels like transmission is slipping, very little power).
So I scanned it and this time had a new code P1754 “A/T overrun clutch solenoid valve circuit malfunction”. I reset this code and the truck was back to normal and has been normal ever since (about 1 week of driving, maybe 40 miles total thus far).
Basically this all points to an issue with the valve body and/or TCU.
Solution to my issue:
Researching has led me to focus on the transmission valve body (which also houses the Trans control unit TCU). It is located inside the transmission and can be accessed by removing the pan. The PNP switch is located on the valve body and so is the overrun clutch solenoid (which receives a signal from the PNP switch).
If you need to replace your valve body, it is not overly difficult. Here is a video illustrating the process.
Finding a replacement valve body can be a bit difficult because there are three different variations. You need to make sure you select the correct one that matches what is currently in your transmission. Here is a good video explaining the differences of the valve bodies.
![]()
Even though they made the video, I would NOT recommend buying from Cascade Trans Parts. Look elsewhere online, or contact your local Nissan dealer parts department. I got a quote for $1,130 for a new valve body from my Nissan Dealer (for reference).
DIVING IN:
After draining the fluid from the transmission oil pan, remove the oil pan and prepare for more drips and a mess. Let it drain and drip overnight.
![]()
Now the bottom of the valve body assembly is visible. This is where my issue became obvious. There were signs of corrosion on the screw heads and bare metal bracketry of the valve body. This is equivalent to a big neon sign saying “This transmission has experienced cross contamination!!”. My speculation is that the previous owner experienced this issue with a failed radiator and had the system flushed and put in a new radiator and called it good. ..then sold me the truck. Hope the band, and clutches and all the other internal parts are ok. I assume they are because the transmission works great except for the occasional CEL codes.
To remove the valve body, remove the bolts highlighted in the factory service manual:
![]()
With valve body out, I could see the extent of the corrosion. No wonder I was getting transmission CEL codes.
![]()
![]()
this shows the PNP switch. No wonder it was malfunctioning. So even though new fluid was flushed through the transmission after the cross contamination (previous owner), damage was already done.
So the next step was source a replacement. I found a seller on Ebay that had the correct part for my vehicle and they had excellent feedback, so I purchased from them. It is important to identify your valve carefully to make sure you are getting the EXACT correct replacement. There are several different ones out that look very similar (as noted earlier in this post).
I will follow up with another post once the new valve body arrives and installation is done.
Another thing to keep in mind is that the TCM in the new valve body may have to be programmed for your vehicle, which requires a trip to the dealer so they can do it through CONSULT. I will see how that goes and see if the truck is drivable.
Update to follow soon!
I have learned all of this because I have been researching and troubleshooting my own transmission in my 2006 Crew Cab V6 4x4 Frontier SE with 175k miles.
Basic Information:
The automatic transmission (both 2wd and 4wd) is officially called an RE5R05A. It is a 5-speed automatic transmission. Gear ratios will vary by application. This same transmission (in slightly different forms) is used in many other Nissans/Infiniti models and other makes/models as well.
Issues:
It is safe to say that most of the issues with these transmissions (as used in the Frontiers/Xterras) can be traced back to two innocent looking hoses connected to the lower tank on the radiator. The radiator can fail and cause cross-contamination of engine coolant and ATF. This means that you will get a milky sludge in your transmission. NOT GOOD.
Many people (and the service manual) call this connection to the radiator a "trans cooler". However, I do not think that is 100% accurate. I believe the only purpose of this mechanism is to accelerate the warm-up of the ATF for better cold-start driveability. The Frontiers for sure (and probably Xterras too) already have an OEM ATF air-cooled heat exchanger located behind the grille, in front of the radiator. You can easily check your own vehicle by peering through the grill on the passenger side of the Nissan emblem.
Here is description of it from the service manual.
On my vehicle I have chosen to bypass the radiator. So all cooling is done with the air cooled one. In my climate and driving, I don’t have any need for extra cooling that could come from the ATF routing through the radiator. Your application may be different.
When I purchased the truck, the previous owner had said they just got the radiator replaced. I didn’t think much of it at the time, but it did have a shiny new radiator in it.
My Issue:
I have been experiencing SES lights on my dashboard. Scanning the OBDII port has pointed to P0850 “Park/Neutral position switch circuit” (PNP switch). I had no drivability issues, so I would just reset the code and continue on. It would be fine for a week or two, then the light would come back on. Did this for a couple months until one morning after resetting the code, the transmission went into limp mode (feels like transmission is slipping, very little power).
So I scanned it and this time had a new code P1754 “A/T overrun clutch solenoid valve circuit malfunction”. I reset this code and the truck was back to normal and has been normal ever since (about 1 week of driving, maybe 40 miles total thus far).
Basically this all points to an issue with the valve body and/or TCU.
Solution to my issue:
Researching has led me to focus on the transmission valve body (which also houses the Trans control unit TCU). It is located inside the transmission and can be accessed by removing the pan. The PNP switch is located on the valve body and so is the overrun clutch solenoid (which receives a signal from the PNP switch).
If you need to replace your valve body, it is not overly difficult. Here is a video illustrating the process.
Finding a replacement valve body can be a bit difficult because there are three different variations. You need to make sure you select the correct one that matches what is currently in your transmission. Here is a good video explaining the differences of the valve bodies.
Even though they made the video, I would NOT recommend buying from Cascade Trans Parts. Look elsewhere online, or contact your local Nissan dealer parts department. I got a quote for $1,130 for a new valve body from my Nissan Dealer (for reference).
DIVING IN:
After draining the fluid from the transmission oil pan, remove the oil pan and prepare for more drips and a mess. Let it drain and drip overnight.
Now the bottom of the valve body assembly is visible. This is where my issue became obvious. There were signs of corrosion on the screw heads and bare metal bracketry of the valve body. This is equivalent to a big neon sign saying “This transmission has experienced cross contamination!!”. My speculation is that the previous owner experienced this issue with a failed radiator and had the system flushed and put in a new radiator and called it good. ..then sold me the truck. Hope the band, and clutches and all the other internal parts are ok. I assume they are because the transmission works great except for the occasional CEL codes.
To remove the valve body, remove the bolts highlighted in the factory service manual:
With valve body out, I could see the extent of the corrosion. No wonder I was getting transmission CEL codes.
this shows the PNP switch. No wonder it was malfunctioning. So even though new fluid was flushed through the transmission after the cross contamination (previous owner), damage was already done.
So the next step was source a replacement. I found a seller on Ebay that had the correct part for my vehicle and they had excellent feedback, so I purchased from them. It is important to identify your valve carefully to make sure you are getting the EXACT correct replacement. There are several different ones out that look very similar (as noted earlier in this post).
I will follow up with another post once the new valve body arrives and installation is done.
Another thing to keep in mind is that the TCM in the new valve body may have to be programmed for your vehicle, which requires a trip to the dealer so they can do it through CONSULT. I will see how that goes and see if the truck is drivable.
Update to follow soon!
a large aftermarket transmission cooler to put behind the grille to replace the OEM one. I decided this would be a good idea considering I am no longer routing the ATF through the radiator. However, I probably wont install it for some time, winter is here and no worry of high ATF temps anytime soon.
