I priced a few torque converter's today, and my question is what is the differences between a lock-up and a non-lockup converter? Give me some pros and cons of both.

Bobby

 

A lockup converter improves fuel economy and top end performance in general. It "locks up" at high speed and thus does away with the 2-3% power loss that otherwise is a consequence of converter slippage. The only reason not to have a lockup converter is if you are racing in a class which does not permit them. Because they are not permitted in high power racing, no one has yet developed one that can hold up under extremely high horsepower. So if you are making huge hp, you don't want one. Otherwise they are a good thing.

Rich Krause

 

So you're saying that with a lockup converter I would run better?

I talked to Art Carr and the said that basicly it wouldn't make any difference performance wise, it would only affect the fuel mileage by making the rpm's stay about 200 higher.

Does it make any difference in tranny temperature?

 

At higher speeds, the transmission catches up to the engine, eventually moving at almost the same speed. Ideally, though, the transmission would move at exactly the same speed as the engine, because this difference in speed wastes power. This is part of the reason why cars with automatic transmissions get worse gas mileage than cars with manual transmissions.

To counter this effect, some cars have a torque converter with a lockup clutch. When the two halves of the torque converter get up to speed, this clutch locks them together, eliminating the slippage and improving efficiency

 

This has got to be one of the best posts on converters.

 

There is little question that if you are talking about a moderate performance street car that a lockup converter is a good thing, though not in any way essential. The only downside is that it's a bit more expensive, but it will improve gas mileage and decrease engine and transmission wear, to a small extent. Yes, it will run a little cooler at cruise.

If set up right, a lockup converter can give higher trap speeds in the quarter mile as well, but they are not much used in racing for the reasons mentioned in my previous post. With a typical setup, the converter will not lock up in the quarter mile and there will be no difference between a lockup and non-lockup converter. Of course, you have to have a way to control the lockup function. A 4th gen with a 4L60E controls the lockup clutch through the PCM. There are aftermarket electronic controllers and a converter can also be setup to have a switch which controls the lockup clutches and there are various other mechanical and hydraulic ways the lockup function may be controlled.

Maybe we could have a more focused discussion if you posted what kind of converter you are using now, why you want to replace it, what your goals are, etc.? Also: what kind of car/tranny are you talking about?

Rich Krause

 

Lock-up is programmed to engage in 3rd and 4th gears, at 42 mph with low throttle, 15% for example. At 40% throttle, it will lock up at 80 mph. Above half throttle, it isn't programmed to lock-up at all. It's mainly for cruising.

So it shouldn't lock up at the track, or effect performance since you'll be WOT.

 

Right now I have the SLP 2600 stall converter and it just doesn't stall high enough since I added the HOT cam, it bogs badly off the line. Best 60ft. was a 1.96 on ET Streets, and that is horrible.

The converter will be going in my 94 Z28 4L60E. I only drive the car on weekends for not very long periods of time. My main goal will be getting the car to run better at the racetrack. Mostly on getting a little better 60ft time, but not being robbed of power at the big end.

So taking what you know about the car, how much it is driven and my goals which converter would you go with lockup or non-lockup?

Thanks for all the info so far, keep it coming.

Bobby

 

Non-lockup will be fine for a weekend car that isn't driven long distances on the highway. I am partial to Coan converters, but you are not talking about a particularly demanding application just call any of the good manufacturers. If you really want the best converter for the track, it's gonna be pretty loose. I am not terribly familiar with the HOT cam, but I would think you want a stall in the 4,500rpm range for that cam if you want to maximize track performance.

What I find unacceptable may be fine for you, but converters over 3,500 or so are pretty annoying on the street, as far as my relatively limited experience goes. You are either going to compromise the track or the street on this one. Maybe someone with the HOT cam will help us out here a little.

Rich Krause