Well, the title says it all I guess. What are the benefits of having one? I am debating on either rebuilding my 4R70W or swapping in a 5spd. My truck just seems slow. I drove my freinds F150. He has the same exact truck, only his is a 5spd. They are 1994 F150 ext cabs. Both have the 302. His is MUCH quicker than mine. And it is almost completely stock. I figure I am losing some power through my Auto tranny, but would like some insight. A local tranny guy suggested a higher stall convertor. Would that help the get up and go any? Sorry for the "new guy" question. Thanks in advance.


Bill

 

All torque converters are "stall" converters.

Torque converter stall is the maximum amount of slip possible in a given converter with a given engine. You can find your stall speed by holding the brake and flooring the throttle. The engine speed you get without the truck moving is the torque converter stall speed.

CAUTION: IF YOU DO THIS FOR MORE THAN ~5 SECONDS YOU WILL DESTROY THE TORQUE CONVERTER!

High performance engines usually run a higher RPM than stock engines. To match the torque converter to the new engine torque curve a torque converter with a higher stall speed is installed.

 

Thanks for the info. I always wondered about that. I appreciated it.

Bill

 

Don't know about your specific model, but some difference in quickness may be due to rear end ratio and maybe tire size, assuming the engines are identical. Higher # ratio and or smaller tire size will allow the engine to get up to speed faster. Negatives are that your mileage might be worse and your top speed may be lower. I raise this point since the torque converter is not always a performance killer. I will mention that the 302 is a bit light on torque and your truck is relatively heavy, so gearing will make a big difference.

As far as torque converters are concerned the other guy had it pretty much right. I'll add a few points. Keep in mind I am no expert and just buy the stuff and read a bunch.

The TC is sometimes a source of loss. It is a fluid coupling, essentially two fan blades connected by ATF. The engine drives one blade, which pushes the ATF which turns the other blade. The fluid coupling is not 100% efficient. BUT, many TC are locking converters which eliminates the loss due to the fluid coupling, but only after a certain speed is reached. I am not sure if the TC lockup under racing conditions is on all the time once speed is reached, ie it might be slipping until you are at an easy cruise state.

A TC can increase the amount of torque transmitted if the TC is designed properly, so you can actually have higher torque to the input of the tranny than you would with a clutch. The problem is that most auto trannies have fewer gears than a stick, so the ratios used may not give you maximum performance as compared to the stick. The stick will have ratios better suited to the engine powerband, usually.
A clutch allows you to get the engine up to the RPM range where it makes power, the TC has to work from near 0 RPM and up so the engine won't come into the power band as quickly. But a high stall converter does allow an engine to get into it's powerband and give you torque multiplication to. So properly done an auto can beat a stick, but it all depends and this is an arguing point for bench racers, from way back.

If you want to have some fun you might look into a higher stall speed converter. It will give you much better launches. But there are tradeoffs. You will get worse mileage, you will need better cooling, if you get too wild with the stall speed your driveability will be affected. I would probably not use a high stall if you do much towing.

Good Luck,

Jim Henderson