Author Topic: Torqueflite 727 wiring question ????  (Read 4332 times)

Offline Pat O'

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Torqueflite 727 wiring question ????
« on: May 12, 2014 - 11:08:11 PM »
I'm trying to figure out a couple of wiring issues I've come across in the engine compartment of my 1972 340 Challenger Rallye. I won't even start in about the dash. Virtually every wire has been cut and spliced at least once, sometimes more.

My first question is the brown wire that runs from the starter solenoid to the neutral park starting switch on the transmission. My diagram indicates that this circuit is S4-18BR/Y*. On my car this wire has been spliced and then connects to the #3 space on the firewall junction box. A second wire from this location, same space #3, then runs to the neutral park starting switch. My wiring diagram indicates on the engine side of the junction block, the # 3 space or port isn't used. On the interior or dash side the #3 spot is indicated as being for the seat belt relay. On this car the seat belt wiring is not connected.

Does this make any sense? Perhaps someone just used this point to splice the two wires together?? Including that "junction" there are 3 splices between the solenoid and the switch. I'm thinking it should just be a single wire from the solenoid to the neutral-park safety switch.

My second question involves a single black wire that comes out of the top of the speedometer pinion gear housing where it attaches to the transmission. This wire worked it's way forward to the drivers side engine compartment and terminated in a single female spade connection, it was taped to a group of wires that terminated in a male T connection (blue and black wires) but are cut off a few inches back in the wire bundle.

I've been looking at my service manual for a couple of nights now and I cannot find a reference for this wire.

If anyone has some thoughts or ideas to throw out to me I would really like to hear them. Right now anything might get me pointed in the right direction.





Offline Chryco Psycho

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Re: Torqueflite 727 wiring question ????
« Reply #1 on: May 13, 2014 - 12:32:40 AM »
OK so maybe they had a short & melted the connector & moved both wires to the the #3 spot in the plug no big deal
 There is no wire to the speedo drive unless you have a later trans like a 518 with a hall  effect sender

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Offline Pat O'

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Re: Torqueflite 727 wiring question ????
« Reply #2 on: May 13, 2014 - 10:58:37 AM »
Thanx Chryco, much appreciate your quick response.

You can tell that there have been a number of shorts in the car. Some of the connections in the bulkhead connector are blackened and melted.

Anyhow, I figure I can clean up the wiring harness a bit and just run a single brown wire from the switch on the transmission to the starter solenoid.

I was told the car had a freshly rebuilt 727. There is definitely a single wire from the speedometer sending unit attached to the transmission. It just isn't connected to anything.

What is a hall effect sender?

Offline Pat O'

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Re: Torqueflite 727 wiring question ????
« Reply #3 on: May 13, 2014 - 11:09:55 AM »
OK, I looked up hall effect sender. Seems to be a hookup for an electronic speedometer?  Perhaps an aftermarket item from Autometer or something. Maybe the car earlier had an aftermarket speedometer. The original mechanical speedometer is in the car now and runs off of the traditional mechanical cable.  :clueless:

Offline thedarkside

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Re: Torqueflite 727 wiring question ????
« Reply #4 on: May 13, 2014 - 01:43:34 PM »
Just my 2c but maybe you should look into replacing the harness completely. I fought it off for a while too but for the time and frustration it took to make everything working again the price was easily justified. The last thing I wanted was an expensive bonfire from some previous amateur wiring. As for the black wire maybe it was being used as power for something which he removed? I had rogue wires which were used for a removed line lock and it drove me crazy.

Offline Chryco Psycho

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Re: Torqueflite 727 wiring question ????
« Reply #5 on: May 13, 2014 - 10:30:38 PM »
SO there should be no wire to the speedo drive

Challenger - You`ll wish You Hadn`t

Offline Pat O'

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Re: Torqueflite 727 wiring question ????
« Reply #6 on: May 13, 2014 - 10:43:21 PM »
Thank you, I am working on the wiring harnesses. I have the engine harness from M&H (yearone), which got me started on this. There are a number of connectors on the dash side and steering column that show signs of overheating and melting. There are also some wires melted together under the dash. My next project is a new dash harness. These are still on back order. I spoke with YearOne last week and they said to be patient since M&H is still trying to catch up on getting new suppliers for for the various connectors and terminals that go into their harnesses.

After reading through the service manual some more tonight I think that the brown wire to the firewall connection and then to the transmission switch is correct. It says the center pin for the neutral starting switch is the ground for the starter solenoid THROUGH the park and neutral positions on the shifter. But I don't see this in the wiring diagram in the service manual.

Finally, I snapped a picture of the speedometer attachment to the transmission.  Just to the right of the threaded cable connection you can see the black wire I spoke of. It ran up into the engine compartment but wasn't connected. I'll take a closer look at this another day.

I appreciate the comments, thanx again.

Offline Chryco Psycho

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Re: Torqueflite 727 wiring question ????
« Reply #7 on: May 14, 2014 - 09:14:41 AM »
the brown wire to the neutral safety switch on the trans should just go from the start relay down to the trans to ground , I don't recall it going through the firewall but maybe it does .
 You have an extra part in the speedo cable , usually the cable connects directly onto the speedo drive but you have the small film can size part in there with the zip tie around it .

Challenger - You`ll wish You Hadn`t

Offline 383RT/SE

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Re: Torqueflite 727 wiring question ????
« Reply #8 on: May 23, 2014 - 05:54:12 PM »
Classic Industries also sells the M&H harnesses (still with the Year One label).  I was able to get a 1970 rallye harness from them a few months ago.  It hurt my pocketbook but saved my sanity versus trying to fix my badly hacked original harness!

Offline ShelbyDogg

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Re: Torqueflite 727 wiring question ????
« Reply #9 on: May 24, 2014 - 08:17:34 AM »
You can take off that speedometer adapter. Save it for future use. It is a sine wave pickup for an electronic speedometer like you thought. With the new ones, you drive a preset distance then push a set button. It counts the pulses and uses that number for the mph and odometer. A hall effect sensor will have 3 wires.
Rob

3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...yes to throttle bodies

My Pace Car restoration thread:
http://www.cuda-challenger.com/cc/index.php?topic=44869.0


Offline Pat O'

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Re: Torqueflite 727 wiring question ????
« Reply #10 on: May 27, 2014 - 05:58:31 PM »
I removed the sender this weekend. The connection point had broken and the wires had corroded, so I pitched it.

I got the new harness from Year one and I am getting that installed. It does include a connection to the junction box on the firewall. Later this year when I do the dash side harness it'll probably make sense. But all is in order now and I've learned a bit more again.

I have to really thank the people on this site and the time they take to respond. I have gotten a lot of great input as I move forward on my restoration. It is invaluable.  :thumbsup: