Over the years, the Allison® 1000/2000/2400 valve body has had four versions. This article is written to help identify each version. The first two versions are five-speed and the last two are six-speed valve bodies. The information will explain casting number and separator-plate combinations that work correctly together.
Diagnosing shift quality concerns can be difficult, especially after rebuilding the transmission. You have just invested parts, your time and expertise into repairing the transmission. You are emotionally invested, which sometimes makes it hard to think clearly. This can be the case when you have a Toyota/Lexus A750E or A750F that has a 2-3 flare after overhaul.
There are some pitfalls that can trip you up with this valve body.
The TF81 (aka AF21) valve body has undergone some changes that you should be aware of.
It wasn’t too many years ago that when you got a vehicle in for a slip or flare the transmission was pulled and rebuilt. When installed it road-tested fine and down the road it went. There were no computers or sensors; there were T.V. cables, vacuum modulators and governors.
Times and cars have changed. Today there are so many things outside of the transmission that can cause transmission problems. You must be sure that your diagnosis leads you to the transmission before pulling that transmission out, especially a front-wheel drive. The last thing you need is to pull the transmission and find nothing wrong inside.
In 2009, Ford changed the casting of the 5R55S valve body and changed the separator plate as well.
Installing the JF506E valve body can be a challenge with the unit on the bench. Trying to install the valve body with the unit in the car is difficult not only because you cannot see the manual valve where it fits into the linkage but also because any sideways movement can damage the gasket.
There are two different manual valves, one for Mazda only and a shorter manual valve for Jaguar, Land Rover and Volkswagen. The valves are the same except the end is longer after the last land on the Mazda valve (Figure 1).
The linear solenoids on the Aisin valve bodies control line pressure, shift pressure, shift/engagement feel and lockup control. A linear solenoid that is sticking can cause all sorts of problems depending on the solenoid and the transmission type. The linear solenoids need to be rebuilt as much as the valve bodies do on these transmissions. The pintles stick and the outer shell (can or shell) can become distorted or loose.
Let’s start with identifying the AW 55-50 valve body and the differences that matter when you’re choosing a replacement valve body. There are four castings, which can be identified by either a letter cast into the valve body just to the right of the S4 solenoid or a blank spot.
A 2-3 shift flare before or after overhaul is a common complaint with the FNR5/4F27E transmission. Even a slight flare can be accompanied by codes for gear-ratio error and solenoid function. The cause for all of this is usually a worn servo-pin bore where it goes through the case.
There are a couple of wear areas in the FNR5 and 4F27E that can cause converter-slip codes to set. Some of the factory trouble-code charts would lead you to believe that a solenoid was bad, because they send you to test the solenoid first. The best thing to do is to determine how the code is setting, and then you can determine where to look for the cause of the code.
Many times you can make a difficult task much easier by using the correct tool. Removing the B1-accumulator retainer on the A750E/F, A760E/F/H and A761E valve bodies can be very tough.