Shift Pointers
- Subject: Code 1781, fourth-clutch switch-circuit error
- Unit: Chrysler 45RFE
- Essential Reading: Rebuilder, Diagnostician
- Author: Frank C. Kuperman, Phoenix Remanufactured Transmissions
This is another one of those frustrating and mind-boggling codes that you do everything to try to get rid of but it seems to always come back. The worst part about this code is that it will not appear when the vehicle is in your shop. Unfortunately, the code is intermittent and its frequency is erratic.
We have seen vehicles in which the code is as frequent as every 50 miles or as infrequent as 500 miles after delivery to the customer. The code is described as a fourth-clutch switch-circuit error, and when the code is present the vehicle will go to limp mode. The first logical choice to troubleshoot would be the solenoid pack, and then inspection of the wiring. In the past we have even gone as far as replacing the solenoid pack, but, of course, the code came back down the road.
“So, what is the problem?” you ask? Well, the source of this code isn’t electrically related, nor does it have anything to do with the solenoid pack. The problem actually lies in the valve body; specifically, a checkball in the location shown in figures 1 and 2. A portion of the checkball will get sheared off (see Figure 3), and when the ball seats on the damaged area a 1781 code will follow, as the ball will not seal completely.
In some instances pieces of this ball can find their way into the manual valve and bind it up; however, this is extremely rare. The good news is that this problem will not cause further damage to the transmission internals. As soon as the code is cleared the transmission will resume its shifting perfectly.
I hope that this little tidbit will save you time and money and, most important, lower your stress level!
