quick question about torque converters.

[JoeinCA]

Hey, I have been looking for a 700r4 transmission for a while, and i have no idea what torque converter i should use.

 

I mean, what stall speed should i am for? (strong 327, into a 77 280z with 3.545 rear gears. I'm making a nice cruiser. )

 

And for the dumb question:

 

Does stall speed mean that at a certain speed (ie. 2000 rpm) the converter locks and no longer slips?

 

thanks for your help.

Joe

[Tim240z]

Try this:

http://auto.howstuffworks.com/torque-converter.htm

[JoeinCA]

okie dokie.

 

so...:

"Stall is the speed at which the converter will hold the engine speed and not allow further gain (i.e., the engine "stalls")"

 

so.... now that i have just spent a good chunk of time reading about automatic transmissions... ive decided to run a manual. (kidding)

 

I still dont fully comprehend what stall speed is exactly... I already knew how a torque converter worked before this. I guess i am just not comprehending the language, from what i read, stall speed only really matters when you are launching. (ie. wont affect normal driving characteristics if converter stall speed is under 3000 rpm)

 

And I found that you want the stall rating to be 500 rpm below your peak power(torque) output.

 

I still don't know what converter i should get.

 

thanks,

Joe

[Tim240z]

Depends alot on the cam you're running. Do you know the specs. If you do, call one of the TC vendors and ask them what they would recommend.

Tim

[JoeinCA]

eh, that's a problem.

 

I bought the engine out of a running nova. The thing sounded great, came with a good Th350, new radiator, headers, new carb, intake manifold...

 

But i dont know what kind of cam it has in it.

 

GRRR why does everything have to be a pain in the ***?

 

thanks for your help tim...

 

Joe

[baddriver]

How do you use your car?

 

For a hard launch at the drag strip, you want a high stall converter so that the engine can spin up and develope a lot of power. (This assumes you have a high revving engine, a high torque engine will launch harder at lower rpm)

 

But, if the engine runs below stall speed while you are driving around town, your tranny fluid will heat up and you could cook your tranny.

 

with 3.54 gears, you don't want a 3000 rpm converter for something you'll be driving around town. I'd stay close to stock or a few hundred rpm higher. Only use a high stall converter on something with steep gears (high 3's or 4's) that has a high revving engine and gets most of it's mileage 1/4 mile at a time.

 

Something a little higher than stock will give you a bit more umph and work well with a performance cam. An engine with a huge cam will require a high stall converter because they won't idle.

 

Many of the 700r4's came with a lock up converter. This lets the engine speed drop below the stall speed without the tranny slipping on the highway. Usually they don't get hooked up in engine swaps and the feature is lost. It improve gas mileage a bit, but if the system isn't set up to disengage when you slow down, it can kill the engine.

[JoeinCA]

I havent used the car yet . I only want to have a good daily driver now.

 

I picked up a used 700r4.. so i dont need to worry about the stall speed at the moment... Though i think it is going to need a rebuild within the year. (more tailshaft play than i like to see, and slightly browned tranny fluid.)

 

I plan on setting up a torque converter lockup kit that will lock the converter when i want, and automatically when i hit 4th gear. it will disengage when my brake lights turn on....

 

Good news is that i have the motor sitting in the engine bay now with the transmission supported with a jack and wood... The engine isnt lined up perfectly though...

 

anyhow thanks for your advice, i will keep that in mind when i need to replace the TC.

 

thanks,

Joe