700R4 Torque Converter Control (TCC)

The original GM pressure switch that had a significant differential between the vacuum at which the contact closed and at which the contact opened, is no longer available. I have tried and looked at several different methods for controlling the TCC but, so far, have found none that work satisfactorily.

1. A toggle switch for manual lock up. Works but is a pain in the ass when you're driving in hilly country. Best used for "tow mode" in a truck.
2. Several vacuum switches have been tried and they all "hunt" at some point, regardless of how you set them.
3. Bowler has a time delay module but it is not "load sensing". It merely has a time delay between when the transmission shifts to OD and when the Torque Converter locks up. It only "unlocks" when you downshift to 3rd.

I am getting ready to try something electronic. I found several 12 vdc time delay relays that I think might work. Here is the one I ordered and at ~20 buck is very reasonable.

https://www.amazon.com/dp/B097GLMDM3?psc=1&ref=ppx_yo2ov_dt_b_product_details

My plan is to wire the brake light switch and an adjustable vacuum switch in series as the input to the module. (CH) The 12vdc input would be wired to that circuit and to the two DC connections. I would hook the NO connection to the TCC solenoid circuit, which includes a OD pressure switch that has to be made. The solenoid I have is internally grounded, so no other connections would be needed.

I would set this up to have an 8 second (for starters) "on" delay to TCC. This would smooth the shift transition into OD. If you step on the accelerator and vacuum falls, the circuit would be broken and TCC would unlock. If engine load leveled off and vacuum increased to vacuum switch set point, TCC would lock up again in 8 seconds. This seems like it would smooth out the "hunting" that you get when you simply hook up a vacuum switch.

Has anyone else tried something similar? Any advice?

 

In the 1990's I put a 700R4 in a rod. The setup was like this info I copied from another forum. I'll try to see if I can find a parts source.


The 12 volts can come from the IGN terminal on your fuse block or any other source of 12 volts. In my case I'm using a terminal on my horn relay to supply the 12 volts and a 15 psi pressure switch screwed into the 4th servo pressure tap (right behind the servo) to send that 12 volts to my solenoid. It automatically locks when it shifts into 4th and unlocks when it downshifts into 3rd.

 

I've been using that setup for years, too. It works OK in lighter cars but my big old 49 Buick weighs a lot and I need a part throttle "downshift", not a 3rd gear downshift. Driving along at 55 mph on secondary roads, I generally just put it into 3rd. Scaling the mountains of West Virginia as I travel to Louisville and Columbus, it lugs the engine too much in lockup.

 

Mine was locked only in fourth gear. When downshifted to third gear, either manually or automatically, the torque converter unlocked.

Is that what you would prefer?

 

Nope, start over.
My kit had an internal, fourth gear pressure switch that I replaced and rewired per instructions.
Worked as described above. Drove it 100k miles.
This was in a lightweight Model A, but with a 4.3L GM V6, I needed the manual shift to third to power uphill occasionally.

 

Thanks, Phil but I totally understand how this works. I usually use the internal pressure switch like the factory. I, also set it up so that it only works in 4th. I am wanting the TCC to unlock automatically, stay in OD and not "hunt" back and forth while driving near vacuum switch set point. The OE vacuum switches did that pretty well but they are no longer available, so i am trying to emulate what they did somewhat. Ideally, you would have a cut in pressure and a cut out pressure that was about 4-8" of mercury apart.

 

I think this is the type of internal, 4th gear pressure switch that is needed:
https://transmissioncenter.net/shop/switch-gm-high-gear-pressure-125c2004r3254l700r41-prong/

This switch is normally open, whereas stock internal switch is normally closed.

 

@justpassinthru
@David Gersic

Any suggestions?

 

Kit?
https://www.ebay.com/itm/2507824901...UOb3ir9hACz7dmb2eWfwbsew==|tkp:Bk9SR7i256elZA

 

Post #9 has wiring diagram:
https://www.jalopyjournal.com/forum/threads/700r4-with-lockup-converter.410947/

 

I never used a vacuum switch. Never had a hunting situation.
I've seen kits with the vacuum switch, but don't understand the purpose.
Fourth gear, locked.
Downshift manually or automatically, unlocked.

 

Hey @rockable
This thread has some good info.
https://www.jalopyjournal.com/forum/threads/700r4-torque-converter-lockup.1297378/page-2
Towards the end of the first page onwards discusses options to omit the vacuum switch.

 

Thanks! I will digest this later today.

 

Without going through the info above, my experience with the 700R4 and a tall rear end ratio (3.08) is to leave the converter unlocked. I put the lockup solenoid on a toggle and switch it on when I jump on the highway. It almost acts like a 5th gear, drops my RPM about 250 rpm. My setup is also in a big, full sized car, and honestly would benefit from a numerically higher rear end ratio, since the highway cruising RPM hovers at or below the engine's power band in lockup.

 

Is my 4L-60 transmission in my 91 S-10 the same as a 700 R4 OR is it a 200R ?
Always get corn-fused.......
Thx
6sally6

 

@rockable
Add a switch in-series with the brake and vacuum switch and use vacuum switch without time delay.
If you're driving at a pace where it's jumping in-out of lockup simply switch it off.

An 8 sec time delay will end up ending in tears [thrown out]
At 70 mph you would cover 273 yards in 8 secs before it locks up.

4L60 is the new designation for the 700 R4
GM upgraded the '700 over the years until eventually the 4L60 [and the 4L60E]

You are better off with the 4L60 [the last of them before they went electronic]

 

We will see. 8 seconds is a starting point. It's adjustable. I think that the timer will reset when the pressure switch "hunts", leaving the TCC unlocked until engine load evens out above vacuum swittch setpoint. If that happens, 3 or 4 seconds might be reasonable. I've done the manual switch on several cars. It's not what I want on this one.

 

Lots of conversions overlook this important little piece. This is the part you are missing. Put one of these in the vacuum tube going to the vacuum switch. It simply delays the vacuum change to stop the tcc hunting in and out of lockup. GM had already solved your problem for you. Junkyard excursion time...

 

If you wire it so the TC stays locked on for a delay, Also wire a "flat to the floor" disconnect [kickdown switch] to the gas pedal. Connect this "in-series"
Sometimes you need that instant disconnect of the TC.

You can also buy 12v 10a [5 pin] timer adjustable relay[these can be switched from delay on, to delay off]
These can be adjusted between 0.5 secs and 6 hours delay

Narva part# 68076
here is the instruction pdf
https://www.12voltplanet.co.uk/user/downloads/User Guide For Adjustable Delay Timer Relay 12V & 24V 10A.pdf

They are popular for integrated DIY turbo timers.

 

When you put your foot to the floor, it downshifts to 3rd, automatically disengaging the TCC due to pressure loss on the OD pressure switch. I do understand how these transmissions work. I'm just looking for a more readily available solution that works. I've already spent 20 bucks for the time delay relay which will only be set for delay on. I already had the vacuum switch, so its gonna cost me 20 bucks to try.

That little volume chamber would probably work, especially if it has an orifice in it but I don't have a part number and junkyards with old cars are few around here.

 

The vacuum delay valve (little black and blue guy shown above) looks like acdelco #14020691.
We need the Standard Motor Parts or another cross reference number, as it is no longer available from GM.

 

Standard Motor Parts DSV35, or any with around an 8 second delay.
@rockable is correct about the 700r4's needing an 8 second delay.
A time delay relay will give the same effect.

 

DSV35 and 14020691 appear to be made of unobtainium.

 

More cross reference numbers, but no current source.
GM part# 14020691 --- Discontinued
ACDelco # 214-479 --- Discontinued
Standard # DSV35 ---- No one stocks and haven't been able to find on-line
BWD #EC342 --- No longer available from manufacturer

 

Im not sure if youve seen this. Its a little pricey but its what I am thinking of using in my 50 ponitac
https://www.summitracing.com/parts/...MI4--VwuPlhwMVLU7_AR01ngI5EAQYAyABEgKBZfD_BwE
It locks up the tcc based on speed and its adjustable

 

Since I consider A/T "magic-with genies inside them"..I have had my 4L-60 rebuilt by a pro when the "sun gear??!" broke. He installed a Corvette servo (whatever that does) and heavier-duty bands and other stuff.
I run B&M Trick Shift fluid because...........I always have.
My only complaint about the tranny is...the govenor lets it shift into 2nd gear about 12 mph...and 3rd about 18-20 !
The 4.3 handles it OK I guess but I would like it to hold itself in each gear a little longer. I also had a shift kit installed and it as nice firm shifts..especially from 1st to 2nd ! My tired(250,000 mile)4.3 will still bark the tires on the shift!!
Once-a-kid...always-a-kid !!
6sally6

 

Have your builder tune your governor with this kit.

https://www.summitracing.com/parts/bmm-20248

 

Before using the governor kit, try tightening the cable a little more, to get later shift points. @6sally6 .

 

Try Ford D32E-AA
Also lot of vehicles use vacuum delay of vapor canisters [vacuum is vacuum]

But personally I think your timer relay idea is worth experimenting with. [it is tuneable]

Brain fade on my part .
You're wanting delay switching on.[engaging lock-up]
This method would get rid of the annoying in-out engagement surging.

Having a switching on delay mode will still get instant disengagement with vacuum drop [kicking down]
You want the T/C to be unlocked before it kicks down or it will be too violent.

 

Hey @rockable , please keep this thread going when you install the time delay gizmo. I am interested to know the outcome, good or bad. I can't see why it won't work, but real feedback is always a plus.