five7kid

iTrader: (14)

... it's the 4-3 switch.

Back in November, I posted a thread asking about it (after I got the tranny back together and filled), and asked about that switch, saying I thought it was normally open but wasn't sure exactly what I observed when I checked it (didn't understand exactly what it was or what it was supposed to do). I was told, no, it's supposed to be normally-closed. I took the pan off again last Friday for the shift kit install, checked it again (but multi-meter batteries were low), it showed continuity.

Today, I finally got new batteries for the meter and checked again - resistance was all over the place, from a few ohms up to over a hundred, but when it did settle down, it was about 25 - almost the resistance of the solenoid coil.

When I inquired at the dealer back in November, they didn't have the switch, had to come from Texas or Michigan. I'm tired of waiting, think I'll just hard wire that circuit (bypass the switch), and get on with it. I understand the 4-3 downshift can be a little rougher, but, like I said, I'm tired of no lockup.

ZZ28ZZ

Don't know if this helps any but, I bought a Haynes manual today and the elec schematic shows the following:
On the tranny connector;
Pin "A" gets power via the "gauges" fuse and the brake switch.
Wire color=PPL (purple?)

Pin "B" is the 4th gear signal line. It gets a ground from the TCC solenoid. I guess when the solenoid is engaged. Wire color=Dk Green. ECM pin# C8

Pin "C" is not connected.

Pin "D" Allows computer to provide a ground to the solenoid to engage it. Wire color=tan/blk ECM pin#=A7
Pin "D" is also connected to ALCL conn pin "F". Looks like you could check pin "F" for voltage. When computer provides a ground, voltage on pin "F" should go to zero.
Looks like you could ground pin "F" and get TC to engage. Computer might not like that, not sure.

Unfornunately I can't tell ya which pin is which on the tranny connector. I looked at mine tonight and didn't see any markings,but;
Pin "A" should have power.
Pin "C" isn't there.
Pin "D" should have continuity with pin "F" on the ALCL.
Pin "B" would be left over..

Jay 727

Some switches are normally open, some are normally closed depending on vehicle application.
If I understand correctly you bypassed the fourth gear switch?
Your converter may not that after a while, that and a firm shifting trans may cause converter failure.

five7kid

iTrader: (14)

"The longer one lives, the more one discovers that everything you know is wrong." Unknown

Anybody got some crow? I could use a plateful right now (tastes like chicken - been there, done that).

Thought I'd do an "experiment" after trying that bypass while the pan was still off - turn the ignition on and check voltages, see if I could hear that solenoid click when grounded, etc.. In the meantime, I had also emery clothed my meter leads, and found that the switch resistance was suddenly steady, and only 7 ohms.

With everything connected, I didn't read any voltage from anywhere to chassis ground. I disconnected the switches (ignition still on), and I have voltage to the 4 gear lead, nothing else. Humm, this isn't sounding right. Pulled the connector from inside the tranny, power on "B", nothing else. Pulled the connector from outside the tranny, power on the light blue wire, nothing else.

"Is my wiring screwed up?" I think to myself. Trace back to where those three join the rest of the ECM harness, strip back a little insulation, same story.

Get a phone call, do some other things for an hour, thinking about how my harness could be messed up this whole time.

I think I'm finally thinking clearly about all this. Helps to understand how something is supposed to work when trying to figure out why it DOESN'T work!

Okay, with the harness disconnected, ignition on, there should be voltage from the purple wire Pin "A" to ground, voltage from the blue wire Pin "B"to ground. With things connected, I should still have voltage from "A" to ground, but since the 4th gear switch is normally closed to ground, no voltage referenced to chassis ground.

In the past, I had replaced the brake light switch, thinking that was the problem. At that time, I verified voltage going through the switch for that wire. It appears now that the voltage is being interupted somewhere between the brake light switch and the engine compartment. I used the entire donor car harness, including under the dash, when I did the engine swap, but it appears something is wrong with the power circuit.

Man, this has been a long road. Is it possible that I can see some light at the end of the tunnel now? Sure hope that isn't an on-coming train!

"The simplest viable solution to a problem is probably the correct solution." Don't know if I'm quoting that quite right, but it's usually true, isn't it?

Now, finish up the Vette servo installation, no by-passed switches, find the power problem to the TCC lockup solenoid (will run a new wire from the brake light switch to tranny if necessary), let's get this show back on the road!