torque converter question. Towing and general hooning

Warning: diesel content 

My question concerns the torque converter stall speed on a ‘99 (late) F350 4x2 diesel (7.3).  To me it seems mismatched for the application.  It’s all stock as far as I know with just a tick over 100k on the clock.  To me, and mines no different than any other I’ve driven or even read about, it seems like the converter’s stall speed is too high (“loose” the street racers used to call it).  What I observe is that my truck  feels lazy until the converter locks.  When mine locks, that truck will get up and boogie (has mods).  Before it locks it seems like all the engine’s power is being lost to slippage.  If I give it even more throttle it will lock early...which is good if you’re wanting it to go.  Seems to me that the stall is too high for towing heavy.  Wouldn’t you want the opposite?  Doesn’t slippage just translate to heat in the fluid and thus the internals?  I’m not as smart as Ford.  Just my observation. There’s even a website done by one of the 7.3 gurus where he shows how to hook up a toggle switch to lock it manually.  Not saying I want to do that, i think it just illustrates that I’m not the only one to observe this.  So the question is: what is it about this system that I don’t understand.  I’m sure there is a valid reason Ford used the converter they did.

I had a 99 F250 7.3  There are instructions for manual TC locks out there. Simple one wire and a switch. (Someone also did an automatic lock too.)  You just have to remember to unlock it when coming to a stop.   It helped with the laggy feeling especially when towing and also helped keep trans. temps down. 

As for your question, I don't know why Ford did that.  

While the slippage looses some power across it, the torque converter is also a torque multiplying device. 

I know ford would de tune things to protect other parts of the driveline. A vehicles hp and torque numbers on paper can often be the theoretical max. Then the vehicles computer controls manipulate things to protect the driveline. My STR (jag manufactured by ford) on paper was the equal of an M5 of the same year. In reality it was not even close. Between the TC and the transmissions shift points being programmed to prevent you from actually getting to all the goodness that the motor could produce it made it in to just another above average sedan. I think it was done to protect the trans and the driveline. 

Does someone offer a tuner for your truck?  That may be the easiest way to tune things to your liking?  

The best automatic transmission for reliability, power and strength will be a hard shifting, knock-your-teeth-out monster that the general public will want no part of.  A torque converter's "stall speed" isn't an arbitrary number; instead can be altered by the weight of the vehicle and the amount of torque the engine produces. 

Which is why you can barely feel most stock automatics shift. And why your trans feels loose after you increased the power of the engine. 

More power will make a given converter stall at a higher RPM, so it's entirely possible your converter is a bit too loose.  Up to a point, higher stall is good, as it lets you get closer to the powerband right off a stop and will make up for imperfect gearing when you bury the pedal.  And while it feels like it's slipping, it's actually multiplying torque.  But too high a stall will make it feel crappy to drive and will make more heat that you have to get rid of. 

Are you sure the truck is starting in 1st gear?

Cooter said:

The best automatic transmission for reliability, power and strength will be a hard shifting, knock-your-teeth-out monster

What?  I do not think this is the case.  Hard shifting takes it toll on gears, shafts, and really all kinds of parts.  It may have less wear due to friction, but it will have a lot of wear due to hard torque spikes that would otherwise be flattened out.

ProDarwin said:

Cooter said:

The best automatic transmission for reliability, power and strength will be a hard shifting, knock-your-teeth-out monster

What?  I do not think this is the case.  Hard shifting takes it toll on gears, shafts, and really all kinds of parts.  It may have less wear due to friction, but it will have a lot of wear due to hard torque spikes that would otherwise be flattened out.

He’s not the first one I’ve heard say that.  Evidently hard shifting is easier on the trans.  Might be hell on everything  else though.

Vigo said:

Are you sure the truck is starting in 1st gear?

It does.  I’m not talking about off the line sluggishness—although come to think of it it could be better.  I’m talking about having to slow for an uphill hairpin to less than 30 or so.  That’s when the converter unlocks.  Then coming out of the corner it’s a dog until nearly 2700 or so rpm when it’ll usually lock again if I mash it hard.  Once it locks again I’m gone.  

ProDarwin said:

Cooter said:

The best automatic transmission for reliability, power and strength will be a hard shifting, knock-your-teeth-out monster

What?  I do not think this is the case.  Hard shifting takes it toll on gears, shafts, and really all kinds of parts.  It may have less wear due to friction, but it will have a lot of wear due to hard torque spikes that would otherwise be flattened out.

You're both right.  As far as longevity of clutches, etc. in an auto goes, harder shifts are better.  Of course, there's a practical limit before you start breaking hard parts or causing overly fast wear to other driveline parts. 

Clutches are weaker than gears and bearings. Which results in a little better reliability if the gears are abused over the clutches. 

On the transmission note: you have to go really hard with shifting and really high with torque before you'll bust gears in an E4OD.  You can firm up the shifts a lot before worrying about the hard parts exploding.

I agree... with your mods, your stock converter will now stall higher.  You can do the TC switch, or set it up to automatically lock above 25 mph, or you can replace the TC with a lower stall (if you can find one).  

If you do the auto lockup (there is some way to do it linked to the 2nd gear shift), be prepared for the lockup to start shuddering.  You can nurse it along for about 30k with a tube of shudder fix, but prepare for a TC replacement

Ford also did you a favor with that higher stall speed.  Strokes rely pretty heavily on boost to make their oomph so they stalled them closer to boost.  With your mods it may not be a factor, but going too low with stall might make it a real slug.

The only F-350 7.3 I've ever been involved with that was chipped seemed to overwhelm the converter.  I thought at the time that the chip needed to come with a new converter.