Speed Control Upgrade

I’m in transition from an ‘85 300 I6 w/ NP435 (with vacuum speed control) to a ‘95 4.9L w/ 4R70W (with electronic speed control)

While switching out the pedal assembly it became apparent that now is the most convenient time to do any wiring changes as it relates to the speed control. Months ago I acquired the necessary servo/ amplifier, cable and about 6” of harness.

I’ve spent the last couple of days reading all that I can on previous threads from Gary, Jeff and others. Very helpful but somewhat confusing as most all pertain to manual transmissions or dealer installed kits. Soooo . . . .

I have a couple of questions.


In the ‘96 EVTM

 - circuit 848, “speed control switch return”
        Do I simply run that wire to ground as Gary suggests in the Big Blue thread?

  - circuit 307, “brake pressure input”
        My master cylinder does not have provisions for this “fire hazard” switch. Do I cap this wire off?
    In essence creating the “open when system has pressure” state necessary to allow use of the controls?

 - circuit 306, “clutch pedal position switch”.
       I will no longer have this switch so I’m assuming that I need to provide a jumper, out of a couple
    female spade terminals and wire, at the connector (as the EVTM diagram implies)

 - circuit 679, “vehicular speed input”.
       I would very much like to retain the use of my stock VSS that is part of my speedometer cable
   (just under the master cylinder) It has two wires, the DG/W would be the signal and the BK should be
   ground. Can I just run the BK wire over to the firewall with a ring terminal and a self tapper? Or does it
   need to be tied into the harness somewhere?

Kurt, I need to look at the '96 EVTM.

There's a lot going on here,..  

But if you're looking for a ground there's one right below the wiper motor.
That stud should be tied to your intake or block.

ALL grounds in the truck are tied together.
If the schematic shows ground it doesn't matter.

Jim - We have the '96 EVTM, but here's a link to the speed control bit: https://www.garysgaragemahal.com/speed-control1.html

I'll see if I can rethink what I did and answer the specific questions.  But I can say that what I did worked and worked well.  And the stock Bullnose VSS works perfectly with the later speed control.

I know it's here, but I don't know it inside out
Appreciate the link though

Thanks for looking into this for me.
After posting, I’m wondering if perhaps I asked questions in a confusing way. It might have been better for me to list the circuit numbers from the ‘85 EVTM, as those are the existing wires in the original harness that I’m trying to marry up to a ‘95 device.
If a comparison chart would help, let me know and I’ll pull one together.

Identifying the circuits you need would definitely be a big help.

Hopefully my phone will stop freaking out and I'll find some time tonight to work on it.

I have my schematics in CAD on the shop computer, so can check out what I did, but not until tomorrow afternoon.

OK, lets see if this helps at all.

First off is the factory installed vacuum speed control.
There are three major connectors between the amplifier that is under the dash and the servo itself in the engine bay.

The larger of the two at the amplifier has 6 wires and is noted as C714 and the connector at the servo also has 6 wires and is noted as C753.
All 6 of these wires seem to simply be a jumper to send info from the amplifier to the servo.

The smaller of the two amplifier connectors also has 6 wires and is noted as C717. Pinouts as follows;

Circuit    Wire Color    Purpose
57          BK             Ground
57A        BK             VSS Ground
150        DG/W         VSS Signal
295        W/P           12+ (15a fuse) HOT IN RUN
151        LB/BK H     Steering Pad
511        LG             Clutch Switch/ Stop Lamp HOT AT ALL TIMES

The '95 electronic speed control.

This device has one connector with 7 wires;

Circuit    Wire Color    Purpose
679        GY/BK         VSS Signal
306        T/LB            Brake Light Switch
151        LB/BK          Common Signal
848        DG/O           Common Return
298        P/O              12+
307        BK/Y            Brake Pressure
901        R/LB            Ground

are you installing ford ecu/tcm or an aftermarket tcm for the 4r70w? how does this relate to the speed control?

TCM will be by Bauman, a Quick 4, shouldn’t have any communication?

Also, TBI will be the Holley Sniper 2bbl, again, shouldn’t have any communications?

The Ford ECU wants to know about the clutch and brake.  Here's how I wired mine.

Thanks for that Gary, but my ecu was removed over a decade ago when I reverted back to a good ‘old fashion carb.

But it is good to find out that the speed control wants to see ground until the brakes are applied, providing 12+

Tarheel Blue wrote

 - circuit 306, “clutch pedal position switch”.
       I will no longer have this switch so I’m assuming that I need to provide a jumper, out of a couple
    female spade terminals and wire, at the connector (as the EVTM diagram implies)

Bear with me, as I'm trying to do this from a phone that's randomly closing the reply window as I try to Peck out a response.

This is on the '96?
With the clutch switch on the back of the master pushrod?
Because on our trucks it's simple to push a spare fuse into the clutch switch connector in order to jumper it. (Perhaps you've switched to an auto, or just want to use the starter to move the truck)

My phone is a nightmare and I can't see enough flipping tab to tab zoomed in, to keep details in my head tonight.

It finally stopped sleeting but this  weather and my knee throbbing make it hard to concentrate.

I'm going to print off the pages I need and puzzle it out after I get some sleep, after 7.

I just got up.
I'm going to see about printing the pages off and playing cryptographer.

Wow, your handwriting is as intelligible as mine.  🧐

It's obviously a sign of Super Genius!   😄

Ha!
I’m not sure about that claim to fame.
No rush, as today is being spent working in the woods, aka, drinking beer and burning logs

As long as you're out there raking the forest, you're doing a great job for America!  🇺🇲

Jim - I'm sure my writing is a sign of sloppiness.  Some have suggested that I should have been a doctor.  But having literally JUST met with my doctor, I think I'm too organized for that.  After we talked a while he said "So, you don't have any complaints.  So, why are you here?"  I replied that "This is supposed to be a Medicare wellness check wherein you ask me what county I'm in and if I have extension cords running across the floor in the house."  He basically did a

Ok, back to the questions, with my answers in bold:

 - circuit 848, “speed control switch return”
        Do I simply run that wire to ground as Gary suggests in the Big Blue thread?  Yes.  It works.

  - circuit 307, “brake pressure input”
        My master cylinder does not have provisions for this “fire hazard” switch. Do I cap this wire off?
    In essence creating the “open when system has pressure” state necessary to allow use of the controls?  No.  The switch opens when there is pressure in the brake system, so the speed control needs 12v on that circuit save for when the brakes are applied.  Otherwise it won't engage.  So if you don't have the switch then you need to take that wire to power, but you will lose a safety.

 - circuit 306, “clutch pedal position switch”.
       I will no longer have this switch so I’m assuming that I need to provide a jumper, out of a couple
    female spade terminals and wire, at the connector (as the EVTM diagram implies)  Yes, or as Jim suggested with a fuse.

 - circuit 679, “vehicular speed input”.
       I would very much like to retain the use of my stock VSS that is part of my speedometer cable
   (just under the master cylinder) It has two wires, the DG/W would be the signal and the BK should be
   ground. Can I just run the BK wire over to the firewall with a ring terminal and a self tapper? Or does it
   need to be tied into the harness somewhere?  You could ground the Bk wire, but I made a "twisted pair" by twisting the two wires together for the run to the speed control.  That helps to cancel out electrical noise in the signal.  But in my case I was running the wires from the transfer case instead of by the master cylinder, so my wires were a whole lot longer and, therefore, more likely to pick up noise.