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Diagnosing and Replacing the Automatic Transmission Kick Down Solenoid Switch
 
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Pelican Technical Article:

Diagnosing and Replacing the Automatic Transmission Kick Down Solenoid Switch

Mike Holloway

Tools:

20mm socket, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Mercedes-Benz R107 (1972-85)

Parts Required:

Kick down solenoid switch (inner) Pelican Part #000-304-28-90-M22, kick down solenoid (outer) Pelican part #000-304-27-90-M22

Hot Tip:

Keep everything clean when working with an exposed automatic transmission

Performance Gain:

Downshift improvement

Complementary Modification:

Change transmission oil and pan gasket

There are several reasons why your automatic transmission may not be as responsive as it once was. As miles begin to build up, the transmission may experience a delay in shifting or it doesn't seem to downshift as responsively as it once did. There could be several issues to address. When this occurs it is a good indicator increased mileage has taken a toll and that the internal components may be wearing out. A quick way to diagnose your transmission is to do the following: When at a standstill with the engine running, shift quickly from park to reverse or drive. Make a note to your self on how long it takes to go from stationary to moving. You should feel a jerking. If the transmission engages immediately that is a good sign you have a strong transmission. If it takes close to one second to engage you have normal wear for a higher mileage transmission (over 150,000 miles). But if it takes two seconds or more this is a good indication the transmission is wearing out. If that's the case, the transmission may need a complete overhaul.

When you achieve speed and pull back on the throttle, do you notice that downshifting is delayed? It could be a simple fix. The kick down Solenoids may have to be replaced. The kick down solenoid switch helps the transmission downshift while at the same time keeping the correct torque and speed to the gears. The kick down solenoid remains open so long as the RPMs of the transmission remain at a certain rate. This ensures that the shift speed to be as close to the maximum designed speed for that gear. When the RPMs go past that rate, the circuit that is created opens and power to the kick down solenoid stopped closing the circuit. These switches are designed to withstand high temperatures, vibration and even the aggressive chemical nature of the ATF. They can still fail. The following explains how to easily change the kick down solenoid.

You will not have to change your ATF but make sure you keep everything very clean. That means you may want to wash down the undercarriage prior to work.

Before you do any work on your car it is important that you wear safety glasses and work gloves. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. Never work on your vehicle if you feel the task is beyond your ability. Always disconnect the battery before working on your car.

The kick down solenoid is located just behind the banjo filler on the transmission.
Figure 1

The kick down solenoid is located just behind the banjo filler on the transmission. It looks like a bolt coming from the transmission. 

Using a 20mm socket, loosen and remove it.
Figure 2

Using a 20mm socket, loosen and remove it.

After the Kick down solenoid has been removed inspect it for varnish build up due to the ATF breaking down.
Figure 3

After the Kick down solenoid has been removed inspect it for varnish build up due to the ATF breaking down.

After the inner kick down solenoid is removed the outer kick down is removed by dislodging it from the lead that is attached to it.
Figure 4

After the inner kick down solenoid is removed the outer kick down is removed by dislodging it from the lead that is attached to it. 

You will want to inspect the leads for the kick down solenoid.
Figure 5

You will want to inspect the leads for the kick down solenoid. Often road debris or vibration can wear down the insulating covering of the wire producing a short. 
Installation of the new kick down solenoids is the reverse of removal.

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Page last updated: Fri 12/2/2016 02:53:56 AM