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info@rostratransmission.com · www.rostratransmission.com

On-off soleniods: failure due to contamination

On-off soleniods: failure due to contamination 3

On-off soleniods: failure due to contamination 4

1. When hard parts fail, chances are the solenoid is already contaminated. Solenoids are electric magnets and will attract steel debris. Discard all solenoids, clean unit thoroughly, and install new solenoids (Rostra brand).

If you have a fuzzy magnet, it's guaranteed the inside of your solenoids look the same. Would you put the fuzzy magnet back in the PAN???

Cut open the filter. What do you see. Metallic debris in the filter indicates debris in the solenoid. Every ounce of transmission fluid passing through the filter also passes through the solenoids.

2. The solenoid is an electromagnet. Certain components will carry residual magnetism and always attract magnetic particles. This accumulates:

In low flow areas of the solenoid.
In s pring pockets
Behind the armature

This is called permagunk, because it will always be in there. Solenoids can not be effectively cleaned. Some are more cleanable than others, but the permagunk is difficult to remove.

Every ounce of transmission fluid that flows through the filter has also been passed through the solenoids. A fuzzy pan magnet is a sign of solenoid contamination.

3. Other sources of contamination.

Metallic particles
Friction material
Sludge

4. Contamination will cause:

Accelerated seat wear and premature solenoid failure, especially with plastic ported solenoids. Seat area is abraded with each armature stroke.
Reduced stroke. Contaminants get stuck in between the spring coils and won’t let the spring compress fully. The solenoid loses some of its stroke. This is a common problem in Mitsubishi and Toyota solenoids. Solenoid oil flow is reduced. Only light throttle shifts are available.
Binding. Debris collects between armature and bobbin. Armature gets stuck. Common examples are the 125 lockup solenoid and 440 lock up solenoid.
Hydraulic failure. Severe contamination will reduce flow and effect pressures through the porting of the solenoid valve.
Contaminated solenoid operation. This solenoid armature pocket and spring are so filled with contamination that the solenoid can never open all the way. When enough pressure can not be vented, the spool valve does not stay in up shifted position. With the additional oil entering the circuit from the main line, the spool oscillates back and forth between the two positions. (Shift hunting.)See an enlargement of photo #4.

Click on an illustration to see an enlargement.