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Discussion Starter · #1 ·
It seems extremely high. There seems to be a wide range that the engine RPMs can fluctuate when in first and second gear. I believe the converter locks for third and fourth. I was wondering why the stock converter has such a high stall speed. Someone mentioned somewhere that this was to protect the transmission and that by replacing the converter with a torque converter with a lower stall speed, you would harm the transmission as more of the engine's peak torque would be transferred directly to the input shaft thus putting more stress on internal transmission components. I want a "tighter" feel between the engine and transmission so to speak. I am looking at actually replacing the entire transmission with a fully built one for this reason. I want that "sloppy" RPM fluctuation to go away (if that's possible). Sorry for rambling. Thank you for reading.
 

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I agree that the factory converter's stall speed is too high. But I wasn't in charge of selecting the stall speed.

I have installed lower stall converters in some 4R100s. I liked a 1600 RPM stall behind a stock 7.3L. I don't believe that the trans needs any modifications if the engine is stock, even with the lower stall.
 
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@Mark Kovalsky - Just curious what did Ford use as the stall speed for converters behind a 7.3?
 

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As I remember (and it's been about 20 years) the stall speed is about 2000-2100 RPM behind a 7.3L.
 

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I agree that the factory converter's stall speed is too high... I have installed lower stall converters in some 4R100s. I liked a 1600 RPM stall behind a stock 7.3L. I don't believe that the trans needs any modifications if the engine is stock, even with the lower stall.
Also curious; going for the 1600 rpm stall speed you like, would a 1500-1700 rpm converter like this work?

Then it seems better mileage would be inevitable since more energy, on average, would be going into turning the wheels rather than generating heat inside the converter?

(Having a transmission guru to ask these questions of is most appreciated.)
 

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Discussion Starter · #9 ·
Also curious; going for the 1600 rpm stall speed you like, would a 1500-1700 rpm converter like this work?

Then it seems better mileage would be inevitable since more energy, on average, would be going into turning the wheels rather than generating heat inside the converter?

(Having a transmission guru to ask these questions of is most appreciated.)
Not a transmission guru by any means but I’ll repeat what I read on another forum once upon a time-Ford set the stall speed so high because they new they had a bad-ish egg with the 4R100.

The more slip the converter provided, the less strain put on the innards of the transmission. Since all of the torque is down low, the higher stall speed meant less overall brute force on the clutch’s and gear sets of the transmission. Since a converter is also a torque multiplying device, it’s high stall speed meant the truck could actually get moving and move heavy loads albeit at extremely high RPMs (which generates tons of waste heat and contributes to poor mileage).

The lower stall speed would be great but we risk damaging the transmission without beefing up it’s interior.

This is what I read and it makes sense to me. I was just wondering if there was maybe another reason lurking around somewhere.
 

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Maybe that's true, I don't know. I wasn't working on the E4OD/4R100 when stall speed was decided.

My viewpoint is that the higher stall speed was selected because management liked the way it felt when they drove it. It made the diesel feel more like a gas engine.

The converter @paul.ps mentioned above should work fine. As for better fuel economy, it certainly is a change in that direction. Will you be able to measure the change? That depends on how much time the converter is unlocked when you are driving. In most cases the converter is locked at cruise speeds so the difference in stall speed doesn't matter at all.
 
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Thanks, @Mark Kovalsky; all good points to consider. Of greatest concern would be any excessive transmission wear on hard acceleration (as @calistroker (thanks also) alluded to).

Unless someone's actually swapped in a ~1600-rpm-stall converter and can post about their experience with it, guess I'd have to try it to find out. Might be great. But If it breaks the transmission, I'd replace with manual. (...um, maybe need a new pcm? This is getting complicated.)
 
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