Majoraslayer
Member
Posts: 322
Age: 35
Loc: Tennessee
Reg: 02-22-04
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11-16-23 06:05 PM - Post#2864225
My truck is a 1988 Chevy K1500 with a 700R4 transmission. Years ago I did a frame swap to convert it from a C1500 2WD to a K1500 4x4. When I swapped it I pulled another wiring harness for it from a junk yard, but accidentally grabbed a wiring harness for a manual instead of an automatic.
The 700R4 has a TCC solenoid to control lockup, so I had to hack this in manually with a relay and can't remember how I did it. While chasing another issue with my fuel pump (it was staying on constantly even with the key out) I noticed that my TCC relay would click on and off when I moved the wiring harness around. I've been going through and improving a bunch of my wiring work to fix bad connections, but I need to verify the correct way to wire the TCC. I cut out my connections to the relay to start from scratch, as I'm not confident I had it set up correctly anyway.
At some point I found a wiring diagram for a TH400 downshift solenoid relay, but I'm not having much luck finding anything specific to these trucks for a 700R4. Does anyone happen to have a wiring diagram that includes the proper connections for the 700R4 torque converter lockup?
EDIT: I think I had this thing wired wrong to begin with. I did find a diagram on AutoZone's site that shows the light blue wire from the ECM goes to the TCC solenoid directly, then the purple/white wire from the solenoid goes to the "RAWL Diode Module" (which seems to be a typo referring to RWAL, or rear wheel anti-lock module). Now my problem is I have no idea where this module is supposed to be to connect that wire. The transmission wiring has a diode in-line with it, but I don't know where to actually connect the wire. Any chance someone is willing to trace their TCC solenoid purple/white wire?
My 1988 K1500 "Truck Of Theseus"
------------------------- --------
- 1995 5.7L 350
- 1989 700R4
- 1988 2WD Scottsdale Body
- 1989 4x4 Silverado Frame |
Edited by Majoraslayer on 11-16-23 08:52 PM. Reason for edit: No reason given.
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 Chevytech
Subject Matter Expert - Senior Member
Posts: 4095
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
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11-17-23 04:45 AM - Post#2864231
In response to Majoraslayer
I looked in three 1988 manuals for this and there were some areas that don't match.
In the fuel & emissions manual on page 10-4 it shows:
The light blue wire from the TCC connector to the ECM is the forth gear signal from the transmission to the ECM.
The Tan / Black from the TCC to the ECM is the ground path for applying the TCC.
The purple wire is power from the gauge fuse then through the brake pedal switch.
In the 1988 light truck wiring manual it shows the purple wire connecting to the RWAL module and going through a 510 ohm .5 watt resistor between the RWAL Module and the brake pedal switch. The power for the TCC does NOT go through the resistor
In the 1988 Electrical diagnosis supplement manual it shows the purple wire for the TCC connects into the purple wire circuit between the brake pedal switch and the 510 ohm resistor. It shows it is feed through the ECM / IGN fuse
So in short the purple wire for the TCC goes through a fuse, then the brake pedal switch, then to the TCC. The ECM Tan/Black wire supplies the ground when the ECM calls for TCC lock up.
There are discrepancies in the manuals on this wiring.
For those of you that are wondering why you are not getting replies to your thread:
Did you give the model, year, engine, fuel system type, and transmission information?
If your vehicle has been altered from stock, let us know about that too. |
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Majoraslayer
Member
Posts: 322
Age: 35
Loc: Tennessee
Reg: 02-22-04
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11-17-23 07:08 AM - Post#2864233
In response to Chevytech
Just to make sure, does "RWAL module" refer to the black plastic electronic ABS module clipped to the side of the master cylinder/ABS valve bracket? That may be an obvious question, but all the parts sites I've looked at just list it as an ABS module without using the RWAL term.
My 1988 K1500 "Truck Of Theseus"
------------------------- --------
- 1995 5.7L 350
- 1989 700R4
- 1988 2WD Scottsdale Body
- 1989 4x4 Silverado Frame |
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Majoraslayer
Member
Posts: 322
Age: 35
Loc: Tennessee
Reg: 02-22-04
|
11-17-23 01:32 PM - Post#2864245
In response to Majoraslayer
So just to update, I no longer need the diagram. It turns out I did set up the wiring correctly originally and didn't actually disconnect any of it. The wires I thought I disconnected actually went to something else entirely, I just lost track of them in a blind spot on top of the transmission. It turns out my hacked-in relay was for the heater circuit on a 3-wire O2 sensor I had installed to help it warm up faster with my aftermarket headers.
All should be good on this problem (for now), thanks for looking into it for me!
My 1988 K1500 "Truck Of Theseus"
------------------------- --------
- 1995 5.7L 350
- 1989 700R4
- 1988 2WD Scottsdale Body
- 1989 4x4 Silverado Frame |
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Chevytech
Subject Matter Expert - Senior Member
Posts: 4095
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
|
11-17-23 01:34 PM - Post#2864246
In response to Majoraslayer
You're welcome!
And yes the RWAL module is the black plastic box mounted out by the master cylinder.
For those of you that are wondering why you are not getting replies to your thread:
Did you give the model, year, engine, fuel system type, and transmission information?
If your vehicle has been altered from stock, let us know about that too. |
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