High Stall Torque Converter Question

[flip888]

I came up with a question a few days ago and i have not been able to find an answer for it yet so i thought i would ask you guys.

With a torque converter that stalls to 3000 rpm, does it only stall to 3000 rpm when the car is not moving (in first gear) or would it make it so it would never send power to the wheels even in 2nd gear or more?

For example, when I'm on the highway right now with my current set up, my rpm is usually about 2200, but with a 3000 rpm stall torque converter would that make it so it would be at a minimum of 3000 rpm?

Also, what about a lock-up torque converter? Ive heard that those are not good for performance (is that true, i don't know), but would that make any difference?

Any info would be appreciated
Thanks

Eric

[drdisque]

the torque converter will not affect your car at highway speeds, above around 35 mph they are always locked up.

[curtis73]

Originally Posted by drdisque

the torque converter will not affect your car at highway speeds, above around 35 mph they are always locked up.

Only if its a lockup converter.

There are three big things to know when dealing with stall speeds. First there are two stall speeds; flash and load (or sometimes called actual). Flash stall speed is what you get when you just mash the pedal from a stop without using the brake. There will be a split second where the engine's RPMs rise, hold, then rise again. This is flash stall. Actual stall speeds (like the ones typically advertised) are the speed around which they hold the engine if you hold the brake and floor the pedal. The other function (and I can't think of the term right now) is basically the input/output torque ratio. Once the converter is pushing the car along the highway, it is still slipping (unless its a lockup converter). It slips at a predictable ratio which is what gives us this number. I hope someone chimes in 'cause I can't remember it.

But to the point; on the highway, there is a difference between input speed (from the engine) and what actually makes it to the tranny because of that slippage. Low stall converters tend to have less slippage and therefore can lower highway RPMs compared to a higher stall converter. The difference is minimal, but all things being equal, just switching from a stock converter to a 3000-stall converter might get you another 200-300 rpms on the highway, that's according to Continental converters... I went through this same quandry a while back

Lockup converters are fine for performance use depending on the tranny. Many of Ford's lockups are not great for long-term reliability. The clutches wear and cause chatter. TH350s after 1982 have a lockup that is a pain and can sometimes cause headaches, but it depends on what you're after. If you have a 200-4R, they have a pretty good lockup circuit that seems to work well. 700R4s tend to lock up early and don't like to unlock, but overall a pretty well-desigend piece. THM200C trannys are pretty much a waste both in lockup TCs and the tranny themselves, so avoid that for performance use at all. Later computer-operated trannys have great lockup circuits, but require the computer to run them.

About your question of lockup operation; If you had a lockup 3000-stall converter, once it locked up you would be operating exactly like a stock lockup converter. The input and output of the TC would be equal regardless of its stall.

I'm not sure what tranny you're talking about, but you can't just add a lockup TC to any tranny. The tranny has to have the capability for lockup. In most cases you can go the other way; from a lockup TC to non-lockup and the tranny signals for lockup but nothing happens. You can't go the other way, though. You'll have a lockup TC but no signal from the tranny to tell it when so it will never engage.

[drdisque]

I knew you were going to come up with a much more detailed description than I could.

[curtis73]

Detailed, yes. Brief, no. I never did learn the art of brevity. I love reading some of my posts where I spend 6 paragraphs describing a simple function and then SaabJohann or MagicRat comes in and says what I meant in one sentence.

[TheSilentChamber]

Originally Posted by curtis73

Detailed, yes. Brief, no. I never did learn the art of brevity. I love reading some of my posts where I spend 6 paragraphs describing a simple function and then SaabJohann or MagicRat comes in and says what I meant in one sentence.

In Curtis's mind every yes or no question deserves a thousand word answer.

[curtis73]

Originally Posted by TheSilentChamber

In Curtis's mind every yes or no question deserves a thousand word answer.

Allow me to give a seven page dissertation on the meaning of "yes" and "no"....

[flip888]

Wow thanks for all the info, i definently learned a lot and that was exactly the info i needed to know.

The transmission i have is a ford AOD from a '90 mustang, i think it has a lock up TC, im not sure (Im still using the stock TC right now), but i ordered a non-lock up from summit.
heh, its going to take fore ever for me to install it all by my self.

[MagicRat]

Originally Posted by curtis73

and then MagicRat comes in and says what I meant in one sentence.

Simple answers from a simple mind!!