700 R4 Lock Up Torque Converter

    J.T. -   I am curious as to the advantages vs disadvantages regarding having your 700R4 transmission lock up in 4th gear compared to not locking up.

    I'm considering a 700R4 installation for my 1970 Chevelle SS which already has a 502 crate motor installed. I've read that the best gas mileage and lowest cruising rpm in 4th gear comes when the converter is locked up due to the lack of slippage. In the other 3 gears the need to lock up the converter is of little importance due to the performance nature of the car.I also understand that you can set up a 700R4 so that via a switch in the cockpit the driver can select whether he wants the lock up on or off which sounds like the best of both worlds.

    Are there any big disadvantages that I am overlooking here? Is a non-lock up converter more reliable?

    Thanks for your help.

    H.C. -   B&M sells a kit that attaches to the trany and holds the I've-got-the-brakes-on signal up. This tells the trans to disable the lockup. There is a small section of speedo cable they sell you and some electronics. You can set the speed of lockup. So if it is set to 40mph no lockup until car is traveling over 40. If you set it to 120, lockup probably won't come on very often, unless you know the local police. I am going to look by trial and error for the correct wire going into the trans connector until I find the "brake" signal. Then I can just put in a switch. In town no lockup on freeway lockup enabled. B&M may be able to tell you how much power/torque should be put through the lockup converter when it is locked up or going in and out of lockup. I got most of this info. off the B&M web page. Good Luck.
    W.V. -   John;
    You pretty much covered it.  One other thing should be noted though. The selection of "lock-up" converters is rather limited.
    A.M. -   The only comment I have come across with the switch setup to turn the lockup on/off is to make sure that it works similar to a cruise control, so that application of brakes will disconnect the lockup function. An over-ride switch may cause you grief if you had to suddenly stop and were not able to manually switch the converter lock-up. However, like Wes mentioned, the selection of high perf lock-ups are limited. Sounds great to me though.

    Archivist: Tom Wilson

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