71 Turbo 400 Kick Down Harness

[engineer_gregh]

Does anyone have a picture of where the harness plugs into the transmission? I bought a harness from one of the board members but the plug at the transmission is not correct. My tranny has two male connectors versus one. Any help would be appreciated.

[SS Tim]

Sounds pretty simple, the trans is the two pin (correct version) for your C/10 402/TH400 truck with CEC/TCS. While the connector/harness is likely off a C30 without CEC/TCS, a single pin. Do you know the year and series the harness came off of?

The trans. used two different pass through plugs depending on the intended application. With the two pin accommodating the added TCS control wire.

Here is a drawing and pictures that will probably help. Please note that the exterior harness pictue is of a single pin, non-emission installation. But I'd suggest you also take a look at the 72 factory service manual around 6T-10 for a description of the systems.
The 71 manual just very lightly touches on it 6T-1.

* VIN/Model Decoders
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* RTFM ... Read The Factory Manuals... download 'em here

[engineer_gregh]

Thanks for the reply Tim. Could I hook up the just the detent terminal and have the kick down work? I believe the harness came off a 71 BB suburban but not sure.

[SS Tim]

Want to say the two pin connector and pass through were just retasked from th earlier switch pitch applications. Thus the detent is the same location on both styles but I can't remember and don't have time now to dig.

If the female connector is offset for the verticle pin you should be good to go.

Also there is a test proceedure in the manuals for the detent/kickdown soleniod you might want to perform. Then if you have a problem you know its in the exterior harness or throttle switch installation.

[engineer_gregh]

Tim is this the test you were referring to?


PRESSURE SWITCH CHECK
Pressure switch in the Turbo Hydra-matic 400 transmission may be easily checked with a continuity tester which uses either the vehicle's battery or a separate source to power the test lamp or meter.
CAUTION: To prevent damaging the pressure switch, the tester used must have sufficient resistance that it does not supply the switch with more than .8 amp of current at 12 volts.

Test lamps which use size 1893 or smaller bulb, will not damage the switch.
1. Disconnect electrical wire harness from transmis* sion electrical connector. If using a continuity tester which has a self contained power source, connect one tester lead to pressure switch terminal of trans* mission connector (see Fig. 7T), and connect other lead to ground. Tester should show current flowing through the switch (switch closed).
If the truck’s battery is to be used to power a simple light bulb type tester, connect one lamp lead to pressure switch terminal of transmission con* nector and connect other lead to a “Hot'’ terminal of the truck’s wiring harness. Check that truck’s battery cables are connected.
2. Set parking brake, apply service brakes, start en* gine and let it idle. Move transmission selector to “Drive” and tester should show current flowing through switch to ground (switch closed).
3. With brakes still applied, move transmission selector to “Reverse” (which supplies transmission oil pres* sure to pressure switch) and tester should show no current flowing through switch to ground (switch open).
4. If above test indicates a defective pressure switch circuit, the transmission bottom pan must be re* moved to service the pressure switch or lead wire assembly.

[SS Tim]

No that is the test for the pressure switch used for the TCS (transmission controlled spark). Remember a test for the detent soleniod but I can't seem to find it. Might be in an earlier manual or an information bulletin I have. Sorry about that. With the trans in the truck, if you hit the detent terminal with a power probe it should cycle the solenoid. Even a resistance test would indicate a short or open as well.

[engineer_gregh]

Thanks Tim. Maybe this weekend I can do some testing. I appreciate your help.

[71CHEVYSHORTBED402]

Good info. here.

Greg, what did you end up doing, and does it work?

Until I read this thread (thanks Tim) I thought the solenoid (number of terminals) may have varied by state emission requirements as opposed year. If I'm reading Tim right this was standard (two terminals, one for TCS), which I believe applies to 71-72 400TH. Like Greg seems to have implied, I'd like to run the stock kick down without the TCS.

Thanks

[engineer_gregh]

Hi Tony, when I connected the single pin harness and activated the kick down switch it was a direct short so I decided not to bother with it. I just manually shift down into 2nd gear.

[71CHEVYSHORTBED402]

Originally Posted by engineer_gregh

Hi Tony, when I connected the single pin harness and activated the kick down switch it was a direct short so I decided not to bother with it. I just manually shift down into 2nd gear.

I didn't expect such a quick response to this "old" thread. Thanks Greg.

Bummer dude, it's supposed to be "oh yeah works great no matter what you do"..........I'm a novice, but perhaps that was at the solenoid because it wasn't working as intended. Did you use the same solenoid? No sign of a ground wire. Apparently it's grounded by the chassis.

I'm just taking a stab at this.....At some point this transmission will be off the truck. I've never so much as pulled a pan, but seems the solenoid would be an easy replacement, so long as it's the right part(s). I believe the single terminal is the detent? Anyway, seems the solenoid with the single prong and the right wire connects should do the trick. That's how my 72 is set-up and it works Could be a mod.

This may be the solenoid, but there's probably more to this. Any additional insight appreciated. Has to be some transmission guys out there. http://www.ebay.com/itm/Turbo-Hydram...3D181397856832