seventysixvette

Got into the transmission today. Three wires come off the electrical connector. Two go to the lock-up solinoid. One goes to a pressure switch.

What's that switch do? I've never seen anyone worry with hooking it up after a swap. I was just wondering why it was there in a stock application.

John

TimAT

If that switch is a single wire, it tells the ECM the trans is in either 3rd or 4th, depending on where it is installed, or could be a TV pressure switch- whatever, a single wire is usually closed under pressure.
If it's a 2 wire switch, it's in series with the solenoid so the switch HAS to be closed before lockup occurs.

seventysixvette

Yeah it's an everyday N.O. one wire. I just couldn't figure out why it's there.
Maybe tells the computer when a certain pressure is reached in a particular gear? Or when a certain gear is reached. Hell, it could be the back-up switch for all I know.

Curiousity just got the better of me.

John

mrvette

MY understanding is that it closes and grounds the lo side of the solenoid when in 4th gear....but I have a DPFI system, and the computer grounds it whenever it calls for.....

BUT being a geet/ET, I also have a console switch that CAN be flipped to ground it all the time, so into 2-3-4 gears it's always locked....gives a nice bump to the shift...

but not recomended for daily use that a way....

cgc

seventysixvette

Per the ATSG manual that switch is a N.O. 4th clutch pressure switch that when closed provides an electrical path to ground for the ECM and a blue wire will hook to it.

Artsvette73

When that swich gets the fourth gear oil pressure it supplys ag round path for the tcc solonoid. You will need to chnge thart switch out to a normally open two connector switch. Gm # 8643710 $8.00 at the dealer. Not a good idea to have the torque converter locked up in any gear below 3rd. Chances of breaking parts goes up two fold.

Here is how you can hook it up

http://www.700r4.com/tech/tcc/relay_.../diagram.shtml

seventysixvette

Guys, thanks for the replys. This is getting interesting! I see a chance to save a few more bucks.





Looks like a simple little cube relay. I'm using one to supply switched power to an electrical strip now. Hmmm, I'm gonna have to get one of those pressure switches quick and see what I can put together.
Thanks again!

John

Artsvette73

If you feel the need to have the shifter correct buy the kit from Shiftworks.com it's cheaper than BTO and it is Shiftworks kit. I got mine off flea bay at a steal.

seventysixvette

Nope. Doesn't matter to me. When I put it in drive I'll know it's gonna shift into overdrive. If I stumble across a kit dirt cheap, I'll take the time to put it in, but I won't pop the kind of money they want for this in the catalogs.

John

seventysixvette

Art I assume you've done this to your vette and that you are using the pressure switch set-up to lock your converter.

Hows that working? Does it unlock when you tap your brakes in fourth? Or does it just unlock for a second, and then lock right back up when you let up on the brake pedal?

It looks to me like wether one uses the N.C. solonoid from Bow Tie overdrives or a brake pedal interrupt switch (a'la cruise control) the interupt is only active while the brake pedal is depressed.

It looks to me like if you just depress the pedal quickly and then let up, you're still in overdrive and still have fourth gear pressure closing (and grounding) the pressure switch causing the converter to just lock right back up.

When you're coasting down to a stop does your converter stay locked until the tranny shifts into a lower gear?

Thanks for any light you can shed on this.

John

Artsvette73

It will unlock when you tap the brake at highway speeds it will unlock and then lockup again.There is so much going on between tv pressure, valve body, and govorner I can't explain.When coasting to a stop it will unlock as the trans is downshifting normally.I am using the relay system through the brake switch also a vac switch so when you hit the throttle the trans kicks down. Some say you don't need it though. The place to really ask questions is here very knowlegable builders they know 200r's. Chris from CK Performance is the man



http://www.turbobuick.com/forums/transmission-talk/

seventysixvette

Thanks, Bro... I was afraid you'd tell me the thing would lock right back up....but I'd forgotten completely about the TV cable.

Of course a body wouldn't be pushing on the gas and brake pedal at the same time (at least on the interstate). Take your foot off the gas and push down on the brake pedal and the electrical circuit is broken immediately. TV cable returns to 'idle' position and the pressure drops. I suspect with the pressure drop the pressure switch opens up and the converter stays unlocked untill you apply the gas pedal again.

Old age or brain farts...........can't tell.

Thanks!
John

BTW, thanks for the link. I'd bookmarked that place eariler and then promptly forgot about it......yeah, it's old age for sure.....

Artsvette73

John
I maybe miss understood you question. If you are at highway speed and you tap the brake it will unlock and then lock again. Mine locks at around 48mph......jack

seventysixvette

Really? That kinda blows my thoughts outta the water.

I guess it doesn't much matter, as long as it unlocks automaticly down shifting....

Thanks! It helps to talk to someone that has already gone through this.
John

redwingvette

I ended up installing the B&M shift controller. Now the convertor will lock-up about 43mph but unlock if I slow down to under 40mph.
What I was getting was an issue when I was cruising and came up on slow traffic or an exit ramp. I would slow down to about 30-35mph which was not enough to cause the trans to downshift and the convertor would not un-lock. This condition would cause the engine to chug/ping. With the controller I can have the convertor lock-up in any gear if I wanted it to as long as I am above the set speed.

seventysixvette

That condition was what I was afraid of. I've pictured having to manually pull the shifter down into a lower gear just to get the lock-up to release.

Thanks for the post.

John

mrvette

What your issue IS is you did not have a relay in the +12 side of the solenoid red wire going to the tranny plug...that relay opens it's contacts when the brakes are applied, removing the 12 from the solenoid in the tranny...unlocking the converter...

and IF you have that and the car still acts as above, you have a defective solenoid in the tranny, and don't ask how I know that, had to drop the pan as it was not included with my rebuild, so I had a mess for 1/2 a day....damnit....