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Pro & Con of Lockup Converter-700r4?



Alright you tranny people, can anyone here can tell me the pros and cons of lockup converters in a 700r4 transmission? I plan on having one installed in the next month or so and here is what I understand so far, keep in mind that the only thing I know about trannies is that if I had to take one apart I'd be lost and have parts left over when I assemble it.

Sor far; I understand a lockup converter is good because there is less heat generated and with no slippage fuel economy is better. I have also been told it's no big deal to run a non-lockup converter as the heat generated is minumal. I have heard that there is a way to control lockup so that in 1-3rd gears around town you have non-lockup, then you are able to lockup the converter when going into OD.

Right now the motor is above stock (not by much) but will eventually be replaced by a strong 383. It will be used on the highway as well as being a weekend town cruiser.

OK, let's have your thoughts and ideas!


I'm not a wiz on this stuff but I have seen power chips advertised that only allow lockup in 4th. Gives you smooth operation around town. Also used to see some retrofits in older non-ECM cars using a shifter mounted switch to lock the converter. That way you controlled it all the time and could even have it locked at full throttle on top end. Power chips allow full throttle lock too, I think.

I know that the aftermarket trans companys that sell 700R4 kits for retro fit use a converter that doesnt lock but has less rpm increase than a regular converter in 4th. Maybe only 200 rpm more at cruising speed than locked.

I think that if I was doing it I would get a complete 700R4 reto fit kit from someplace like Phoenix Transmissions. You will get a trans built and calibrated to your car and driving style, the right converter and all the pieces to put it in plus a 2 year 24000 mile warrenty. I'm sure there are others here that have done this that know more from experience than I but I hope this helps.

I don't find a web site but the phone # for Phoenix Transmission Products is (817)599-7680. They are in Weatherford TX.

Switch - Cool!


I have a switch that I manually throw whenever I hit cruising speeds that locks in the TCC
on my TH350. I cut it in at the switch circuit where the brake pedal cuts it off. Was no big deal
and it keeps it from popping in and out (typical with '81's). A switch is sweet. Suggest an
illuminated switch too. That way you always know when it's on. It will really gag the tranny
at low speeds if you forget to turn it off.

Good luck.......... Nut
Tom & Nut,

Thanks guys! I think I will find one of the conversion kits with a switch and do that part myself, I have a real good tranny shop here so that should only tie up the Vette for 2 days. The switch idea seems to be the best way to go, I want to be able to control this thing to lock up only at cruising speed.

Off to research more parts and spend, spend, spend.......
The switch idea is a good one, just use it sparingly. I've heard that running the TCC locked most of the time can eventually damage your transmission. As was stated earlier in this post, your car itself will probably tell you when it doesn't like the converter locked. In the world of Buick Grand Nationals (which I also own), locking the TCC goes down as one the of the all time best bang-for-the-buck mods you can do. By simply bridging the proper terminals in the ALDL connector under the dash with a paper clip, you can knock 0.2 seconds off of your quarter mile time on average (results may vary). Just don't forget to take it out after the run!

700R4 and Lockup Switch

I also have a switch for my lock-up. I only use it on the highway. I do get 22mpg on the highway!!

Just looking through the new Jeg's catalog and found a switch and harness to manually control converter lockup.


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