Can you please explain?

[etg]

I don't really know anything about transmissions, so when the shop I am gonna order my tranny from asked me whether or not i wanted lockup I just stammere....I dont know. Can anyone explain what lockup is for and does, the differences between lockup and no lockup? It's on a 700R4 transmission.

[JimKshortstep4x4]

A torque converter without lockup has some slippage because of the design of torque converters. Transmissions with "lockup" has the electrical/mechanical means to engage a locking device in the torque converter. When the torque converter is "locked up", the slippage is eliminated.

Lockup is a nice feature to have but it requires an electrical hookup or in the case of later model cars, the computer is tied in with when the lockup occurs.

Jim

[etg]

thanks jim. So the purpose is to elimintate slippage? What exactly is the that hehe. I'm telling you I know nothing!

[86swb]

Did the guy who asked you which you wanted not know the answer for your question?

[VetteVet]

Here's a little info on lockup converters.

http://www.700r4.com/faq/whatlock.shtml

[etg]

thanks guys. THey all just had different answers that were kinda vague. The tranny guys said that lockup makes it so that at about 50-55 mph it locks up and then everything rotates as one, in unison, thats wat he said.

[Longhorn Man]

in an overdrive aplication, i would say go with the lock up. It does add quite a bit to the cost, but an overdrive by nature will slip more than a non overdrive.
In a non overdrive aplication, I would skip it just for the cost and weight savings. It can be banificial, but IMO, the cons outweigh the pros.

As for what slippage is... A converter works like 2 window fans in a metal housing filled with oil. When you turn on one fan (we'll pretend the engine is running fan #1) it will spin to a predetermined speed. The throttle position... or your right foot, will determine the speed. Then, the other fan, which is placed directly in front of the first fan, is not powered. However, the air blowing through fan #1 (think of the air as tranny fluid) will cause the other fan to turn also. This second fan, is what powers the tranny This enables the engine to be running, while the vehicle is stopped and in gear. you can demonstrate this, by reaching outand stopping fan #2 with your hand.

Now, just by the laws of physics, and the inefficency of this primitive contraption, you will not get 100% of the motion to the second fan. You can compensate for it by making one fan bigger than the other, but in all reality, there will be a power loss. This is what's called slippage. Fan #1 is spinning at 2500 RPM, and fan #2 is spinning at about 2300 RPM.
Now, if you opt for a lock up, at a predetermined speed, and load, a mechanical connection is made between #1 and #2, think of bolting those 2 fans together. #2 will make every single move that #1 makes.
This eliminates 200 or so RPM, and can increase your MPG a little, or, if the gearing is way off, or a very underpowered overweight vehicle, and a lock up can actually DECREASE the MPG.