A look at an uncommon problem with a common unit
The RE5R05A made its debut in 2002 in the Infiniti Q45. Since then, it’s become standard equipment, an automatic rear wheel drive transmission found in most models for Nissan and Infiniti. Variants of this unit are found in some Kia and Subaru applications as well. Nissan used this unit up to model year 2015 in the Armada. Now, at 17 years old and a production life beyond 10 years, these units are in the marketplace in abundance. The design of the unit makes it a transmission that will remain rebuildable for many years to come. Most of the common failures in this unit have been identified and documented, however, as this unit ages, we are beginning to see new failure patterns. Let’s take a look at an example.
It started as a typical RE5R05A transmission job. A 2007 Frontier had water contamination and no other complaints. The transmission came in as a bench job from another shop. It was rebuilt with frictions, steels, pistons and a new valve body from Nissan. The shop that pulled the unit replaced the radiator. Everything appeared to check out correctly on the bench and the unit was installed.
After the transmission was installed, the truck was sent to the Nissan dealership to have the TCM programmed. When it was picked up from the Nissan dealership, the technician mentioned that it had a harsh 1-2 shift. The vehicle was driven and the harsh 1-2 shift was verified. There were no codes or external conditions that warranted further diagnosis, so the unit was pulled out for a closer inspection.
The unit was disassembled with hopes of finding some evidence of clutch trauma or a failing sealing ring; anything! After finding no such evidence, it was assumed that the valve body must be faulty. So, another valve body was ordered from Nissan, but it wasn’t scheduled to arrive for 2 to 3 weeks (At this point, it was just before Christmas). In hopes of a “better case scenario”, the original valve body was disassembled, cleaned and inspected. The solenoids were cleaned and the seals were replaced. The valve body was reassembled and installed into the vehicle with fingers crossed. To everyone’s surprise, it worked perfectly. It was released back to the customer for them to enjoy for the holidays.
Unfortunately, happiness ended when the vehicle returned after the New Year with a different problem. It was immediately assumed that the original valve body had issues. By this time, the valve body from Nissan had arrived. It was installed and the unit worked perfectly (again)! The customer was released with his vehicle.
A few months later, it came back again with the same harsh 1-2 shift. Since the vehicle was out long enough to relearn any bad shift habits, the unit was immediately removed for a much closer inspection. Again, the initial inspection showed no signs of concern inside the unit. So, a different unit was built and installed. The vehicle was driven with the same results.
By this time, everything was pointing towards something other than the transmission being the issue. But, what could possibly cause a harsh 1-2 shift only?
Looking at a clutch apply chart (figure 1, page 12), it shows that the direct clutch comes on for the 1-2 shift. Since the direct clutches weren’t burnt, they must have held without slipping. The focus then would be on what affects how quickly they applied. This brings us to the question of shift solenoid performance or hydraulic circuit performance being the issue. Since four different solenoids were used (2 included in the new, OEM valve bodies, 1 original and 1 in the core rebuilt unit), it was highly unlikely that the solenoid mechanical integrity was an issue. So, attention was given to the hydraulic circuit.
With the original unit on the bench, air checks were performed using regulated air pressure to see if any sealing issues would show for the direct clutch. Using regulated air pressure, it took 70 psi to get the direct clutch to move and hold correctly. This was not good.
The direct drum and support were inspected closer to see where the issues were. No concerns were found with the direct drum piston, seal or sealing surfaces. However, while inspecting the support, the dynamic (rotating) sealing rings were fitting kind of loose in the lands. As a matter of fact, the top ring land measured 0.018” clearance between the land and a new sealing ring. That is more than 3 times the expected clearance of 0.005”.
A closer inspection showed a step-type wear pattern in the ring land groove (figure 2). This seems to be an amazing feat since the ring lands are steel and the rings are a much softer material. Unfortunately, this is very difficult to detect with the naked eye. Using technology that most of us have could assist in the inspection process for checking the ring lands.
Use your smart phone to take a picture of all the ring lands with the rings removed. Once the pictures are in your phone, you can blow them up on your screen or you can send them to a computer and blow them up even more. This will allow you to see details that your eyes can easily miss.
A support was ordered and new sealing rings were installed. The clearance was verified to be within specifications and the direct clutch was reassembled. An air check with regulated air pressure showed an apply pressure of 50 psi easily applying the direct clutch. This is good!
The unit was reassembled using the Nissan OEM valve body. A test drive was performed and confirmed that the problem was solved!
Someone may be wonder what happened the previous times when the unit worked correctly and was delivered only to return with the same issue? I’m glad you asked! It turns out that in the previous cases, the test drive was not long enough to expose the underlying issue. With the transmission fluid below normal operating temperatures and the OBD2 systems not ready, the computer strategy calls for higher operating pressures. The higher pressures, along with cooler, thicker ATF was enough to keep the 1-2 shift quality in the acceptable range.
Moving forward, here is what is recommended with the RE5R05A unit. On top of the typical items to address, thoroughly inspect ALL sealing ring lands for clearance issues. Ensure that all of your sealing rings are fitted and are within the 0.005” specification. Perform a thorough air check using a maximum of 50 psi regulated air pressure (figure 3). If the unit doesn’t check out right, you may need to try different sealing rings. Always keep your original sealing rings handy for comparison and use OEM rings if needed.
Things aren’t going to get easier as these high tech units age. They will come into our shops and challenge our skill as well as our sanity. That’s when it works to take a deep breath, collect ourselves and go back to the basics. Always remember, no matter how crazy these units get inside, they all operate on the same, basic principles of the automatic transmissions that we were accustomed to back in the days of the 3 speeds. A systematic approach will invariably lead you to the source of your problems, even on a tired RE5R05A.
A special thanks to Clayton Williams from C&S Transmission Specialties for the information and pictures!