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manual tcc on/off switch

4K views 19 replies 5 participants last post by  Mmusicman 
#1 ·
How do u wire a independent on/off switch to the tcc circuit
I have heard of using a toggle id prefer a switch that can
Be manually turned on but will turn off when brakes are pressedttherefore unlocking tcc
 
#3 ·
No its not I think its the dumb maf code but I can bypass it I wanna what kits r out there do they unlock w the brakes being applied? ?
 
#4 ·
Yes they control it just like the van did. It comes on in 4rth. Disconnects in 3rd and lower. Brakes on disconnects it. about 190 bucks for the 4l60E kit.

There one for a 700R4 for 90 bucks. It a dinosaur type. Uses things that are user friendly and adjustable. It is for using trans in cars that didn't have computers. 4rth gear pressure sensor and a vacuum sensor.
 
#9 ·
The kits they had randy were way more than 190
I think there a indipendent controller I wanna
Just wire a switch
 
#13 ·
chevymaher said:
highmilegmc said:
Can the brake switch be used to cut off power?
Yes that is what the relay is for.
Exactly! That's how I'm going to wire mine (for now)... using a "momentary" switch to "latch" a relay.. but signal from brake lights will "unlatch" the same relay. It's crude, but will work perfectly.

The way I'm going to attempt this is use 12v + power output from relay to latch itself (momentary switch throws 12v signal to initialize the relay) and have ground side of signal attached to brake light side of the brake switch. The heavy resistance from the brake lights filaments (when off) will provide the "low" needed for the relay to be activated.. which will un-activate when brake power is applied (since there will now be 12v signal on both sides of the relay, unlatching it. This requires standard incandescent bulbs (1157 or equivalent) to work. I've done this type latching setup before.. it works great.

Here's a crude drawing:

TCC-Latch.jpg


This circuit is using a standard Bosch type relay (or equivalent)... available cheap at any auto parts store. The purpose of the diode is to prevent the brakes from reverse attempting to activate the relay while the TCC is off. Any standard power diode will work (available online or at Radio Shack before they go out of business). If you can get a relay with "dual 87" outputs (not 87a), then the diode would be un-needed.

Certainly, the TCC kit with vacuum and 3-4 pressure switch is the better way to go... but is more complicated, more timely, more expensive, and requires dropping the transmission pan along with some internal mods. Note: this option doesn't give you the option of running TCC locked up in 3rd (direct) which might be desired for heavy towing, or climbing.

This simple relay/switch wiring mod can be done easily, and obviously for under $10. This allows for "manual" operation only, with the exception of the brakes which would deactivate the circuit. Note: a vacuum switch could also be wired to work with this circuit for a little bit more of an automatic operation... with manual switch activation and brake deactivation.

This mod will activate the TCC in any gear.
 
#18 ·
highmilegmc said:
Mmusicman what benefit is to locking tcc in all gears?
There is NO benefit to locking up in all gears (that I am aware of). Also.. shifting while locked may even be detrimental.. I certainly wouldn't intentionally attempt it. Only lock up once you are in high gear on the highway.

But as I explained, there is a benefit to locking up in 3rd (direct 1:1).. which is highly useful if heavy towing. My 2000 locks up in 3rd (with tow button on).

It's just one of the side-effects of this simple mod... and not done intentionally.
 
#20 ·
UPDATE: I figured I'd post and update on my manual TCC lockup results.

I discovered that the later model 700R4's come with a built-in 4th gear switch, as mine did. It sends a ground signal out thru the main 4 wire connector, which I'll explain shortly.

You literally can simply send 12v (and ground) to the TCC lockup (pins A & D)... and everything just works from there! A switch actually isn't even needed if you were to wire from switched ignition power. [see figure 1]

TCC-Schematic1.jpg


Typically, wiring from pins B and D are fed to the ECM (which I removed from this figure).

I also discovered it will NOT lock up in 1st or 2nd gear in any way whatsoever, despite manually activating the circuit. Power actually opens the hydraulic circuit that allows lockup when certain conditions are met. Mine however will lockup in 3rd and 4th, if you ground the TCC lockup (pin D).

Another nice surprise to learn is that it will also disengage hydraulically when you apply more throttle, even without the ECM. NO vacuum switch is needed either! For me... manual lockup in 3rd was too "jerky" with shifting (and unneeded), so I decided to use the 4th gear switch and use it in 4th gear overdrive only.

The trick is to ground the TCC (-) wire to the 4th gear (-) output.. which goes to ground when you hit 4th gear. [see figure 2] Then (again depending on throttle pressure)... TCC lockup will automatically engage! You literally twist the 2 wires together (pins B&D), and apply 12v to pin A.

TCC-Schematic2.jpg


The circuit above suggests using the brake switch to disengage power while braking. This isn't actually absolutely necessary, but it will give you less jerking and a smoother ride while braking. I haven't done this yet, since I mostly use lockup primarily on the highway and haven't had any issues. I will probably add the brake switch power interrupt later at some time.

I opted to NOT use my manual latching circuit (which would have worked fine).. since the lockup works completely automatically with the 4th gear switch.. just set it and forget it! I did install a lighted toggle switch for the option to engage/disengage 12v to the lockup circuit. It lights up in 4th gear when lockup is engaged. Nice!

Mine goes into 4th (and lockup) about 35-40 mph with light/normal throttle. During harder acceleration, there is no lockup (even though manually engaged) until you ease off throttle and reach normal cruising.

With a moderate hot-rod cam I found mine can be a little "jumpy" at low rpms in 4th... so I typically disengage around town, and use lockup primarily on the highway. But with steady maintained throttle pressure at slow speeds (other than a short) stretch it's fine. Otherwise in slower local traffic it's best to let the torque converter do it's work.

As an added non-related bonus... I decided to use the 4th gear switch to also send a signal to an A/C bypass relay to the electric fan... which is not needed at cruising speeds. When I hit 4th... the e-fan disengages automatically. Nice!

I don't know what year they started including the 4th gear switch in the 700R4's.. but it sure was a blessing to find it in mine! No parts or mod's needed.. it's all already there!
 
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