A518 only has the OD solenoid on the valve body. There is no lock-up convertor. Personally I have only ever replaced 1 solenoid....they rarely give problems unlike the Governor ones in the RE transmissions . Has your speedo by chance been quitting intermittently??
The speedometer has been rock solid. Here are a few scenarios that describe what is happening:
1) Coming down a hill at 75mph and let off the gas abruptly (someone cuts you off) and it will shift out of OD.
2) Sometimes you have to let off of the gas to get it to shift into OD. The shift seems fine; it seems to be more of a user input problem. The TPS seems like it might be related to something like this.
Thank you for the insight on my issue. I love this truck and use it often so getting our problem resolved is a high priority.
