I am working on my 86 k10 with a 700r4. I have a question concerning the wiring. The 4 pin connector has a wiring harness plugged into it. The harness runs from the tranny to the fire wall where it splits and one side runs to a vaccum sensor next to the brake booster. The other side was unplugged and has 2 wires. Does anyone know where the other side of this harness plugs into?
CK5
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700r4 wiring question
- Thread starter v8jeeptj
- Start date
I'm just guessing here, is it the brake pedal switch connector?
GonicGM
1/2 ton status
Inevitably, a harness needs to enter through the firewall and under the dash. There is a rubber boot where the harness passes through the firewall. The harness will connect to the fuse box for power, brake switch, the 4wd relay and I believe the ground connector as well. If you have an ECM, it should connect to that as well.
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ripped all my wires out and went with a BTO lockup wiring kit
vacuum? I don't remember having any vacuum sensor on my '85...
vacuum? I don't remember having any vacuum sensor on my '85...
GonicGM
1/2 ton status
A vacuum switch mounted next to brake booster was used on non-ECM controlled trucks with lockup converter. This includes 1980 and later TH350C and 82-84 C6P chassis 3/4 ton 8600 GVW with TH700R4. Not sure if any ECM controlled trucks used the vacuum switch.
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moneypit_K5
1/2 ton status
wasn't aware any 700r4s had anything other than a TV cable, ecm or otherwise. interesting.
GonicGM
1/2 ton status
All TH350 and TH700R4 had TV cable as far as I know for line pressure and shift firmness. Lockup is controlled by ECM or switches or both, completely independent of TV.
moneypit_K5
1/2 ton status
right. maybe I should have clarified.I meant I didnt realize they had a vac solenoid to control shift firmness or line pressure.
GonicGM
1/2 ton status
They don't, on TH700R4 The vacuum switch is for lockup, nothing to do with shift firmness or line pressure. I don't know the range, but the vacuum switch for lockup is closed for a range of cruise vacuum, relatively high vacuum, deceleration, it opens, relatively low vacuum, acceleration or uphill load, it opens, unlocking torque converter.
if you can't put it back to original, that BTO kit I mentioned has done me right so far. It just locks up in 4th. I don't know if the original locked 3rd or not. This uses a new piece inside the pan, external switch, and new electric switch on the brake pedal.
but I have an 85 that came with a CCC setup, now it has nothing but the BTO kit
but I have an 85 that came with a CCC setup, now it has nothing but the BTO kit
GonicGM
1/2 ton status
FWIW...
On non-ecm controlled gas TH700R4, path of vacuum is from carb to temperature switch, then to vacuum switch. Until operating temperature is reached, no vacuum to vacuum switch. Therefore no lockup in 2nd or 3rd at cold operating temperature. 2nd and 3rd lockup at operating temperature and cruise quality engine vacuum. 4th gear always in lockup by default.
On non-ecm controlled gas TH700R4, path of vacuum is from carb to temperature switch, then to vacuum switch. Until operating temperature is reached, no vacuum to vacuum switch. Therefore no lockup in 2nd or 3rd at cold operating temperature. 2nd and 3rd lockup at operating temperature and cruise quality engine vacuum. 4th gear always in lockup by default.
xenomarine
1/2 ton status
Depending on year/model etc, I've read that they will lock up in 4th, 3rd and 4th, or 2nd 3rd and 4th. Seems wacky to me.
Is it a red 2-way Weatherpack connector (the kind with the little towers around the terminals)? If so, it's for EGR control. For a couple years before TBI, there wsa a vacuum relay mounted above the DS valve cover. It broke the vacuum to the EGR valve, so EGR was controlled by a thermal vacuum switch, but also this signal from the transmission. I can't remember if the signal was lockup or just cruise. The 700 had two signals for lockup - one electric from the vacuum switch (near brake booster) and the other hydraulic based on TV and governor pressure. Both had to be present for the TCC to lock.
wish I had known that when I removed all the vacuum lines off the 86...might not have fried the tranny...
FYI, I was directing this at the OP, v8jeeptj. So do you have a pic?
IIRC, it looked like this, but in red:
See the EGR/Purge valve?
I removed the factory carb and intake off of my k10. The wiring harness runs from the 4 pin connector on the tranny and up towards the engine bay. Once at the engine bay it splits into a "Y" with the red connector you have pictured. I assume this red connector plugs into the vaccume sensor thing. Where do I run vaccume from this sensor thing onto the motor. And where do I plug the 2 plastic connectors on the other end of the harness? One plug has 2 wires and the other has 3 wires.
FYI, I was directing this at the OP, v8jeeptj. So do you have a pic?
IIRC, it looked like this, but in red:
See the EGR/Purge valve?
