Another 700r4 question? TC lockup...

[79Silv4x4]

A few years ago I had my 700 in my 83 rebuilt by Jet Performance and their performance kit uses a non-lockup converter. The only thing I needed to do was add a heavy duty tranny cooler. Ran it for years with no problem. . .

[86k10]

Everyones giving there 2 cents so I might as well too. I have been building these ever since they came out in 82 and have tried different things on my own, some work and some don't. I have yet to see a shift kit that works in one. And I wonder why everyone thinks you need a vacuum switch to unlock the tcc. That's handled just fine by the tv valve and besides the only vacuum switch the factory used was to allow the trans to warm up a bit before it would engage and that was controlled by water temp. If your putting one in an older vehicle you can run it through a brake switch but that is not needed for it to work properly either. It's just wasted money for all these wiring kits you all have pictured. And depending on which wiring harness you put in it, you can have lockup in 2,3&4 or 3&4 or just 4. And I don't pay much attention to those who say the 87 & up are better than the old ones. I see just as many newer ones in my shop as the old ones. I just converted my old 74 C 20 from a manual 4 speed to a 700 and I don't have either a vacuum switch or a brake switch on it and it works just flawlessly. I do run it through a toggle switch so I can shut it off when in town. But regardless they are a good trans when built and adjusted right and will give you double the life of any 350 or 400, both of which are fine transmissions but hey when you've been rebuilding them as long as I have the numbers don't lie.

[N2TRUX]

Originally Posted by 86k10

Everyones giving there 2 cents so I might as well too..... I do run it through a toggle switch so I can shut it off when in town......

What I am trying to avoid is using a toggle switch. I want the tc to unlock on it's own when the vacume goes low, or I apply the brakes. Correct me if I am wrong, but isn't that the way the factory does it? I know that doesn't mean it's the only way to do the same thing, but I figure it's one of the best ways.

The advice of how to set it came came from my bro-n-law. He is the one that built the tranny, and since he has been building transmissions for 35 years I feel like he has a pretty good idea of what works too...

[86k10]

I was just saying I use a toggle switch because I just don't care for it locking up while driving in town, you can go without it and it will take care of itself no problem. As I said before the factory used a vacuum switch that was activated by a temp switch in the engine coolant. But it's function was to keep the tcc from locking until the trans was warmed up a bit, it had nothing to do with unlocking it. I would say maybe your bro in law and I better get together and share some ideas Anyway all I'm trying to say is for it to work correctly you don't need all this aftermarket stuff.

[Bob Gervais]

I have a possible solution as well. A friend of mine, Paul Nimz, has made some devices for another car club I belong to. He named them the "VAK", Vacuum Accessory Killer. Basically, it switches at about 2" of vacuum and kills all the accessories (alternator, AC, etc). The cars these were originally designed for, Taurus SHO's, do this at WOT, however this device allows the car to kill the accessories sooner.

I'm thinking that this type of vacuum switch arrangement is what is used to control the converter lock/unlock function, and that Paul may be able to make the switches needed for trans swaps, for a lot less money. In fact, he's told me he could make vacuum switches for around $25. I'm not sure if it would work or not, I don't know what level of vacuum this needs to switch at, because I have not swapped a 700R4, but I figured it's worth a shot.

Paul is a great guy to deal with, and probably has done more electronic modifications to his own vehicles, and others in the club, than he probably cares to remember. He has a great deal of knowledge about the subject, we'd just need to tell him our needs.

For anyone interested, his email address is pnimz@v8sho.com. He's told me that anyone that is interested can contact him, and specifics can be worked out.

[Grande Rojo]

Ken, I ran a 700 for about a year and never even used the lock up. My tranny builder said I would only gain about 200-300 rpm in lock-up. So unless you are doing alot of hiway driving I would not use it.
What rear gears are you using?? 308's ?????? what the cam specs in your new motor??

high gears+overdrive+big cam = not good
you need to find your cruise RPM

I just got a th400 "built" I did not want to blow the 700 behind my new 454 bigblock!!

[Bob Gervais]

I thought running without the lockup would fry the TC? I've done a little looking around though, and it seems you can get a non-lockup TC as well, maybe that's the way to go?

[86k10]

No you wont fry the TC you'll fry the whole trans, lockup convertors generate lots and lots of heat, especially when in 4th gear. I tried a little experiment with my truck one night. I had around 100 miles of interstate till I was home and I thought what a perfect time to check the temp difference between lockup and non lock. The temp was in the single digits and running with the tcc engaged, the trans temp showed a little over 100, I have a toggle switch to shut it off so I drove the next 20 miles unlocked and the temp was up to 250 in just that little ways. So believe me you need lockup or it will run way to hot.

[REPO1]

Ken,

Do you have a part number from Painless for this kit? I am in the process of getting a 700 into my truck as well.


Thanks!

[N2TRUX]

Here ya go. It's Painless Wiring #60109 I bought it from www.summitracing.com I did a search and found it here cheaper so they matched the price of 125.00...

[REPO1]

Thanks!

[apstguy]

You do definitly need the brake switch though - if you lock up the brakes in OD and don't have the switch in there, your transmission and engine will be directly connected and the wheels stop moving and... use your imagination. I have a 2200 rpm converter and it gets the tranny hot in summer. Always use an external cooler on a built up tranny or if towing. 86K10 is right about the shift kit - they don't seem to work right in 700s. Modify the valve body instead of a shift kit.