Re: Stewart's 1955 Packard 400

Posted by Stewart Ballard On 2023/8/23 15:42:07

I dug around some more and found some notes I made in a 700R4, rebuild book. It wasn’t much but was enough to jar my memory, somewhat.

I did the trans rebuild in 2016. This included a new pressure switch & solinoid for the 4th gear lockup that is normally computerized. I had never done a trans rebuild and so I needed a step by step DVD for most of it. The lockup mod was pretty straight forward once you understand what is going on.

For those of you that that do not know, the 700r4 was designed to work with a computer (CPU) in mind. The CPU controlled the gear lockup. Of course we don’t have a CPU.

In 2016 there were only a couple pre-made kits for this mod and they were always sold out. Today, more companies have got involved and the kits are pretty easy to find. I will not be buying a kit since half the work was completed 7 years ago. It's not a big deal, all I want to do is manually provide power to the 4th gear lockup solenoid. This solenoid is only used at highway speeds when you want the over-drive.

In 2016 I was told that all that was needed was a power wire from the ignition ACC bolt to a manual on/off switch (on the dash) and a ground wire. Since that time it has been discovered that a wire run from the ignition provided more amps than needed for the job and sometimes caused the internal pressure switch to fail (I have no idea how common that was). So now it is popular to wire in a relay between the plug (on the trans) to the manual switch. The relay needs 3 wires, I found a wiring diagram below.

I have read that some guys like to place the manual switch somewhere on the floor to activate it when needed with a press of the foot. However, the most common location is on the dash. Truth be told there are many ways to wire this up. I am not sure how they all work but a Google search will lead you down all sorts of rabbit holes.

I have some new parts on the way now to complete this project we will see if I am as smart as I think I am.