Keep the Torque Converter Locked full Throttle (6.2L)

[john8662]

Ok,

Thinking out loud and I'm looking for some solutions either electronic or not for a test.

Engine platform: 6.2L

Transmission TH700R4 Electric Lockup Converter (fac config).

The typical configuration of the 700 Allows the torque convertor to unlock under full throttle during a shift down event.

I'd like a way to force the Torque converter to lock ONLY under full throttle, or by a switch on demand.

So, basically the opposite of the factory setup, but I don't want a switch to have to remember to flip, and then back off.

Any ideas?

Thanks!

J

[SimonUK]

Use the kick down switch as per the TH400 to power the lockup solenoid. should be able to knock up a basic wiring loom to suit.

This will force the 700r4 converter to lock up in 2nd, 3rd and 4th.

Just make sure you know which wire is which on the plug on the side of the tranny as there were several wiring variations.

[john8662]

So the TH400 kickdown is opposite, cool!

I have a few of those laying around, since i don't need the other portion of the TPS which operates EGR.

Now, I gotta figure out how to keep it from locking in 2nd.

Thanks for the tip!

J

[SimonUK]

I'm not sure how the TV cable unlocks the 700r4 converter at full throttle. I'm assuming it somehow dumps pressure to the switch(s) on the valve block thus cutting the supply to the lockup solenoid.

I'm sure some of our more knowledgeable contributers can give us a better explanation.

I know when you floor the throttle on a 400 the kickdown switch supplies 12 volts to the tranny so I'm assuming it should also keep the 700r4 lockup solenoid energised if used this way.

Think you'll need somebody with a good understanding of the 700r4 valve block to disable it from locking in 2nd though.

Regards Simon.

[john8662]

I'm happy you found a part I already had that would do the job, that I hadn't realized existed...

I'll likely wire a TC lock switch to energize the new TH400 Kickdown switch, to enable the feature.

The beauty of this modification is I won't have to remember to turn it back off after a run.

This is like a safety.

I can still wire an additional switch to enable TC lockup for street use.

Thanks again!

J

[Robyn]

Howdy

The lockup system on a 700R4 can be very complicated depending on the year model.

The best years for ease of operation would be the 88-90

You need to have a valve body that has the valving in it.

If yours does not many times the valve body will have two aluminum slugs filling the bores instead of the valves.

When this is done the control is totally in the hands of the computer.
The electric solenoid on the front corner of the tranny (Same side as the dip stick) runs the show totally in these.

The solenoid can have one of 19 different wiring styles to suit the different vehicles they were used in.

They all have varying color coded wiring plugs too.

1- you need to have the valves and springs in the valve body to shift the critter hydraulically. This will give you lock in 2-3-4 and if the electric solenoid is turned on, you can maintain lock on compression down to about 24 MPH.

This setup will give you a fail safe so the engine cant be killed.

2- The best wiring type is a "Type 3" and it uses the 4-3 pulse switch.
The TCC will unlock for a few seconds during the 4-3 downshift only.

To do a 4-3 downshift with the TCC locked is pretty brutal especially when applying maximum power.

I tried my Blazer with a hydraulic only setup and the solenoid shunted by installing a 3/16th check ball up in the solenoid snout.

Too problematic and too rough coming down.

I really dont think this is all that good for the unit either.

The part number for the solenoid you need is a 8654123 and can be had at most tranny supply houses or good O'll Ma GM

The two inner connectors go to the 4-3 pulse switch which if the tranny is viewed from the bottom up is at the rear of the VB just about in the middle. The other two may or may not have switches in them.

Your tranny may aslo have a temp switch depending on the model.

Just use the 4-3 pulse and leave the others to plug the holes.

The new harness will plug into your existing plug in the tranny. It snaps in easily.

The power wire to the solenoid will be ther "A" terminal which is, if viewed from the top outside the outer front pin.

Your truck may have this wire hot all the time and it may not.
If yours is hot all the time just cut it and switch it to get the control you desire.

If yours is not a hot wire constantly just hook up a fused hot source that is switched via the ingnition and then use it via your extra switch..

To reflect a little. The 700 TCC system has a pretty touchy setup and locks and unlocks far too often when even cruising.

The setup you desire will give you pretty much the best of both worlds.

If you forget to turn the power off the tranny will do its thing all by itself and lockup after the 1-2 shift at about 35 under moderate throttle.

With the switch off you can use it around town without the anoying bump bump bump of the TCC as well as preserve the life of the thing.

The TCC in the 700 is prone to early failure due to overuse.

You could even wire it through the brake switch if you desire to give you a hands free while driving too (Just a thought)

Doing the change on the VB to get the proper valves is no biggy.

A good tranny book such as that sold by ATSG will do the trick for you.


Pretty simple modification and it should give you what you want.

Good luck

Robyn

[john8662]

A little more background...

The trans is an Art Carr Extreme unit. It has a manual valve body (not full-manual) though.

The transmission was wired for an '82 system, it has just one wire going to the transmission, the inside of the trans has one solenoid with one wire.

I think it's pretty simple.

When asking about the trans I was told NOT to lock the trans in 2ND, as i'd damage it, so I was making the assumption that since I was told, that it could be forced to lock in 2nd...

I guess I need to ask more ?'s to the builder to see how the VB was configured, it's the later VB with the Aux VB.

I was concerned about the converter staying locked when it wasn't supposed to if I left the manual switch on. So from what you're saying it'll automatically unlock under 24MPH anyways?

This is why I wanted the TCC to lock only under full-throttle (race), and then unlock after not full-throttle, to prevent having to turn the switch off.

Hmm..

J

[joed]

You probably already know this, but...

My 82's trans. was rebuilt by the previous owner, so I'm not sure of the setup, but I do know it locks the TCC with the 1-2 shift. This really seems to lug the engine, especially at low throttle. This also makes for a rough 2-3 shift.

I got tired of this, so I set up a toggle on the 12v supply wire to the TPS, which feeds the TCC. On mine, it's fed from the brake switch, so with the brake applied, no voltage to the TPS, so no TCC lock.

With the switch "on" it's in auto mode and will lock the TCC once the TPS moves some (10%, maybe) and the brake not applied.

I switch it off for driving around town, which does make it much smoother without the TCC locking.

Thanks. Joe.

[Robyn]

John

With the Carr tranny I cant tell you how they set up the VB
If it has the valving there will be no adverse effects.

Still to get the best operation you need a 4-3 pulse switch in the system as well as the hydraulic controls..

Does your tranny use any internal switches ??
Very few did not have at least one switch.

Beings its an aftermarket tranny its anyones guess as to what they may have done.

Let me know how the internals are wired.

You can mix and match stuff on these to get almost anything your heart desires though.

What are you bolting up front of this little critter to hold on to???

Robyn

[john8662]

Does your tranny use any internal switches ??
Very few did not have at least one switch.

I had the pan off the transmission during it's install in the truck to install a deeper pan with a plug, I only saw very few wires on the inside. I only recall a home-made type harness going to one solenoid facing the front of the VB. But my memory has faded since then, and it was late at night of course...

I'll give the builder a call and get some more specifics, because this thing isn't quite fine-tuned yet.

What are you bolting up front of this little critter to hold on to???

A pretty fun combination that's producing consitent numbers under 15.5 in the 1/4 mile.

It's faster than the '97 LT1 Z28 6-speed Camaro I once owned for a short amount of time.

Working on more things to shave some time (like locking the TC), then add more fuel, etc. etc.

[john8662]

Turns out the TC is probably locking.

I spoke to the fella who built my trans and cleared up a few things about how it works.

It's setup to ONLY lock in 4th gear, so that's why I don't get a lock.

I don't drive it much in 4th, my "testing" range near my shop isn't much longer than 1/4 mile, and it's not street legal currently.

The VB is setup with one switch and one solenoid, you were right Robyn.

I asked how I can get lockup in 3rd.

Simple, drop pan, shunt the switch, and it'll then be able to lock in all gears.

It was then suggested to use a switch to manually engage the TC, but with one gotcha, that if I didn't remember to turn it off due to the configuration it would start chuging the engine near stop, so the above suggested TH400 kickdown switch will be used as a fail safe.

Hoping to get to do this mod soon (before this weekend). If not, in between the next race.

In the middle of a gear ratio swap out, 3.08 -> 3.42

Robyn, How would a pulse type switch help?

J

[High Risk]

I have a toggle switch hooked up on mine. All your do is run the GROUND through the switch. It's activited by the grounding of it. I lock mine up in 3rd and let it go after that usually. When you hit the brakes it'll disengage it also since you just run it through the ground. Brake lights takes the power from the solenoid through that switch.

[john8662]

I have a toggle switch hooked up on mine. All your do is run the GROUND through the switch. It's activited by the grounding of it. I lock mine up in 3rd and let it go after that usually. When you hit the brakes it'll disengage it also since you just run it through the ground. Brake lights takes the power from the solenoid through that switch.

I think the lock may be controlled via one wire on an 88-91 model with a ground, because one of the other wires is likely a hot wire already.

My trans only has the lone single wire.

It has to be a Hot because otherwise you'd have just a grounded case, then a grounded solenoid, solenoids need ~12v to activate.

J

[Robyn]

Best overall setup is to install the valves in the VB so it will run hydraulically and then the solenoid can remain on and you wont chug the engine as it will release below 25 anyway.

Robyn

[john8662]

Well, the TH400 Lockup setup has been installed.

I've been doing some "tweaking" on my '82 pickup.

Just a few modifications for more power. The major upgrade included a 300HP marine injection pump, set at this level (for now) to replace the maxed out 4911 with modified governor.

Got Dual stats on the engine now to finally match the Penn V-belt HO water pump that had been on the engine since build. Got nearly all the grimelins found and squashed with this setup, it DID make a difference in cooling, especially making the QUICK temp swing back. This is all back roads 1/4 testing of couse, track tomorrow.

It runs quite a bit faster now, not sure what the numbers are now though.

Anyways, the lockup on a TH700 is incredibly slow.

I have a switch in the cab that I can flip to manually engage the TC when the TH400 switch is closed, under full throttle, I nearly don't get a lock.

So, all the trouble and it didn't change a thing.

The switch in the valve body has been bypassed (that only allowed lockup in 4th).

I can manually lock the TC otherwise too, forgot to turn if off once too, kinda interesting... Chuga Chuga, oops, flip the switch.

When manually turning it on, same thing won't lock due to pressure or something at the power level I'm running.

The bad though, when dropping the pan to do the switch mod, there was a LOT of clutch dust on the bottom, more than I've ever seen when serving a transmission, although the fluid didn't look bad draining out the drain plug in the pan. I have around 30 passes at the track with this trans with the previous power level.

Now, I can't use 4th gear under WOT because it slips (or feels like it) when going from 3rd to 4th, Shoot.

Looks like it's 4L80E conversion time!