Doug nash 4+3 shift issues
 

I am the proud owner of a 1984 with the 4+3. The overdrive has began acting erratic. At times it will drop out of overdrive while on the highway. At times it will not engage overdrive when it its turned on. I have changed the fluid and filter. This helped with hard shift it was having and that clunk as it shifted out of overdrive automatically when reducing speed. I suspect a pressure switch problem in the overdrive. Is it possible to jump or bypass this for diagnostic purposes?

Yes, you can just jumper the pressure switch for testing purposes.

I will give that a shot when i get it up on jack stands next time. I may be putting off the inevitable of changing whole setup to a 6 speed. 😑