[Note: This article is written for the original 4PK model, the newer 4PKS and 4PKS-R models include a built in 4WS mixing mode.]
Yes, your old Futaba 4PK can do 4WS mixing for rock crawlers and monster trucks. It’s not too hard to setup either. You can set it up to do front 2 wheel steering, 4 wheel anti-phase steering (tight radius), 4 wheel “crab” steering (sideways driving) and even rear 2 wheel steering, using each mode individually with the numerous buttons and dials on the 4PK.
To get it all going you need to use of one of the most powerful features on this radio, Program Mixing. Program mixing allows you to set one channel to respond to inputs from another channel. For instance, you can set the throttle channel as a slave to steering and when you turn the wheel left or right it can reduce or increase the throttle in response. That’s just one minor example of the innumerable things you could do using this feature.
So lets get right to it and setup your Program Mix for 4 wheel steering. To start with, we have to find the Program Mix application. It is only available on Menu Types BIGCAR and Level 3. So if you’re still using the default menu type Level 2 (and why are you really?), you’ll need to change to one of those menu types before you can access it. To do that, press right on the navigation pad to bring up your menu. Move the highlight over to the bottom right and click on the *MENU-T label.
Once in the Menu Type application, use the + button twice to change over to Level 3, then press down on the navigation pad to Exec and press both the + and - buttons at the same time to activate Level 3. Now you’re playing with power!
Press the End button to exit the Menu Type app and return to your menu. You will now notice a whole lot of new entries on your menu. The two we’re interested in are labeled PMIX1 and PMIX2. Highlight one of them and click the navigation pad to enter the application. It doesn’t matter which one at this point, you’ll be using both to setup all 4WS types.
On entering you’ll see the following screen with the default settings.
You’ll need to change all of the following settings. Use the navigation pad to move the arrow to SLV and use the + button to change it to CH3 (or CH4 depending on where your rear steer servo is plugged in on the receiver). Move down to MODE, and use + button to change it to ACT. Now navigate back to the top and use the + button to set LEFT and RGHT to +100.
Once all that is done, press the End button to return to your main menu, select the other PMIX entry and enter the application. Now you’ll set it up basically the same as above, but for LEFT and RGHT you’ll want to set them to -100.
Press End again to return to the menu, now we need to set a couple of the buttons on the transmitter to activate these program mixes. On the main menu press the + key to move to page 2. Select the entry labeled SWTCH and click the nav pad to enter the app.
Using the nav pad select the button you want to map the function to and use the + button to scroll through the options to select PROG MIX1 or PROG MIX2. Now set another button to the other prog mix. The buttons on the transmitter are as follows: PS1 is the button on the bottom side of the steering wheel; PS2 is the button on the transmitter hand grip, just below the throttle trigger; PS3 is the button on top, to the left of the antenna. I recommend PS1 and PS2 for this setup as they are momentary buttons (active only when holding) whereas PS3 is a locking button (active on pressing, inactive after pressing again).
Now, with those set, any time you hold one of those buttons and turn the steering wheel, then your 4WS will activate. Finally we need to set up for rear steer only. Which is as simple as going back to the menu by pressing the End button, moving up to the DIAL entry and entering the app.
Now you map one of the dials on the 4PK to channel 3 (or 4, again depending where you have your servo plugged into the receiver).
Highlight whichever dial you’d like to use for rear only steering and use the + button to select CH3 (or CH4). The dials are as follows: DL1 is the top dial on the hand grip; DL2 is the bottom dial on the hand grip; DL3 is the dial on top, to the right of the antenna. I use DL3 for this setup.
Once setting the dial, you might want to adjust the dial rate, which determines how much the servo moves per click on the dial. Press right on the nav pad to put the arrow on the number, then use the + button to increase it. I set mine to 10. If your rear only steering isn’t turning the way you want it to, you can also move over once more to the NOR option and change it to REV, using the + button, which will reverse the direction the servo moves.
So now you have total control over 4WS on your model. As I said at the beginning, Program Mixing is the most powerful feature of this radio. And it can be made even more powerful using a feature called 2nd Condition. More on that in a later article.
A lot of the features that are available in the newer 4PK models (4PKS and S-R) are also available in the original model, but you can find the original model for much cheaper on ebay.
Click for more Futaba 4PK how-tos.