One of our customers rebuilt an AW55-50 and had repeat complaints of a 2-3 shift flare. Everything on the transmission side of this complaint was corrected and rechecked. Everything on the valve-body and control side of the complaint was done, checked, verified and looked at again. Resets/relearns – you name it, they tried it. Eventually another valve body was tried, but the car continued to have the 2-3 flare.
2004 and later AX4N/4F50N units have a new design for the gasket between the case and case cover. Changes in the area of the neutral/reverse accumulator (Figure 1) required a small change in the opening for the accumulator. The 1.490-inch-diameter opening used on 2000-2003 units was increased to 1.810 inches in 2004.
The story goes something like this: The customer came in to the shop complaining of no overdrive in a 4R70W. There are no codes or obvious external causes, but the complaint is verified on the road test. The unit will not go into overdrive.