Aisin style transmissions are notorious for having failed pressure and clutch control solenoids resulting in various shift complaints. Intermittent or consistent flared shifts, harsh shifts, coast down bumps and clunks to name a few. With such consistency of failure, it often times causes a deviation from checking into other types of failure that can produce similar complaints.
Rarely, a Nissan Maxima with unequally inflated tires will cause downshift bumps and clunks during turning maneuvers. This has been misinterpreted as a typical solenoid failure or the need to reprogram adaptation.
Another type failure that causes various shift complaints with Aisin style transmissions is a loss of lubrication pressure. Lubrication pressure is sent to an assorted group of counterbalance pistons within the transmission to assist in applying and releasing a clutch. It also assists in preventing the clutch from being applied by centrifugal force. A loss of this pressure compromises proper shift control producing various shift complaints.
The transmission used in the Nissan Maxima is called the RE5F22A. This style transmission is used in the Saturn ION and VUE called the AF33-5, the SAAB 9’3, 9’5 and various Volvo vehicles called the AW55-50SN/51SN.
Checking lube pressure with this type of transmission or any other Aisin style transmission is quick and simple and should be an initial diagnostic step before any work or pricing begins. With Nissan’s Maxima, measuring tire width with a stagger gauge should be another initial check. Both steps can be done quickly before even considering solenoid failure. This could prevent days of hair pulling hours the few times these shift complaints are not caused by solenoid, valve body or reprogram adaptation issues.
Lube Pressure Testing
To do a quick lube pressure test, locate the lubrication pressure tap on the end cover of the transmission. There should be approximately 5 psi at approximately 150°F. If less than 5 is observed (many times 0 psi will be seen), an internal transmission problem is the cause or contributing cause to the various shift complaints.
The reason for a loss of lubrication pressure can be caused by regulator valve bore wear in the valve body and/or bushing wear in the gear train. If the bushings are worn, check for wear in the area where the output gear bearing assembly spline into the case.
A loss of lubrication pressure in combination with a sloppy gear train due to worn bushings and case, downshift clunks and bumps are “bound” to happen. All the right tire sizes, valve bodies, solenoids and reprogramming adaptations will ever compensate enough to overcome the banging of gear binding and release on a shift.
A simple step of checking lubrication pressure gives you those X-ray eyes into the box before any work or pricing has begun and can help you make money instead of losing it, in more ways than one.
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