I've heard many, while chassis dynoing their cars, will make a pull in 3rd with the converter locked. I understand the thinking. I also have the capability to do so.
My question, and it pertains to the holding capacity of the clutch itself, is aren't they putting themselves at risk of smoking the clutch?
I've an Edge converter with a single disc and my understanding is that it's really designed to maintain a cruise RPM in O.D. and not much more. Of course the triple disc has greater holding capacity but the racers I'm talking about don't have, for the most part, anything other than a single disc. Even if it is a "woven carbon fibre" by Edge, how's that going to hold up to WOT while on the rollers? FTR: In my case this is about 450-500 lb-ft TQ.
Edge suggested no.
Anyone here with relatable experience?

 

I still have my old 3400 Edge converter with a single disc, and I can check my drag racing log-books and notebooks (and older posts on my build thread from 2020-2021) which might remind me if i did lock it up on the track or not. I know I have been locking up the single disc Yank 3800 converter on the track for the past two years now; surprisingly its holding in there fine still! I also locked it up on the dyno and it picked up just 1 hp I think. I definitely feel it when it locks up, both on the highway and on the dragstrip in 3rd gear, and its still doing its job. I can tally up the passes on it too, but its gotta be at least 60

 

I've heard many tales of applying the lockup in 3rd. I was cautioned against it by Andre at Edge although now I feel compelled to revisit that conversation.
That said, I also asked this same question at LS1 Tech. One fellow there, Frank, formerly of Performabuilt transmissions, answers a lot of questions about automatics. He appears to have a pretty good insight into this.
His comments were:

"I do not advise locking the converter at WOT unless a triple disc , Yes high risk of smoking the lockup clutch."

"...many get away with it, But there is a risk that should always be considered and an expensive risk as for instance shredding a lockup clutch is a complete tear down of the trans to clean out and or possible pump damage."

Now lockup while cruising is a different matter. That's a reduced amount of torque that needs to be clamped and I can see, and am going to experiment with, how there could be a benefit with lockup in 3rd. I was often at the MPH where OD is too sluggish (unless unlocked via by dash mounted toggle) and 3rd is just right. But always up against the converter is building excessive heat and we know heat equals death to an automatic. So there is that. It wasn't until this latest install that I wired in the option for lockup in any gear so I'll give 3rd a whirl.

WOT and OD locked up is something else again. It was achievable back in the day with the B4C cars that prevented a 4/3 downshift at full beans. This let cops catch the bad guys. I will say that I don't know if they achieving lockup during those pursuits. Maybe yes, maybe no? Remember though that those cop cars of then and today, aren't particularly high output so less lb.-ft to control. But, while inquiring about WOT in locked up OD, I was told that further mods other than just the B4C throttle valve was needed. I had a desire to get to an open road event and try for 140 MPH for several miles. So my take away from that research is that it's not a viable option unless you're willing to risk toasting the transmission. Again, some dialogue elsewhere led to this comment from another builder.

"There's a few issues
First, it can be tough on the band.
With a good flat drum, a nice wide band, and a sonnax 4th super servo. Combines with a big feed hole and no accumulator...I've had good success.
Locking the converter at the same time you shift to 4th is problematic. Lots going on there for fluid demand. Also fairly hard on shafts/splines/etc"

Anyway, let's hope it ends in fun and games and not bench pressing another 4L60!

 

I read all that over a few times. I remember chatting with Andre at edge and also Dave at Yank about the lockup and how I use it. Both cautioned against it also but yank told me I’d probably be ok for a good while with locking converter on a pass. I took it a step further and lock it up during a 150 nitrous shot because, well, I’m stupid but hopeful it won’t smoke the clutch. Eventually it will and that would indeed require a trans teardown. Not something I wish to do, but I do understand I’m probably on “borrowed time”.
I’ve considered removing the converter and sending it back to Yank for inspection and to upgrade to the triple disc clutch, but that might end up happening next winter. Thanks for posting the TCC info, I’m torn on what to do as the lockup has netted me better timeslips (and great rpms on the highway), but I don’t want to kill a transmission in the process of using lockup.

 

I'll not be concerned about 3rd lockup while cruising. There are places in the countryside here (which I live in the middle of) which are well suited MPH-wise to stay in little d. I agree that OD and lockup are game changers on the highway. I've mentioned before how those elements combined with a stingy AFR and too much timing made for a decent return in the MPG department.
As for the chassis dyno, your comment about seeing a 1 HP gain is notable. I wouldn't necessarily be chasing a big number (but who isn't interested in that?!) as I'm looking for the HP and TQ RPM peaks. But having an idea what the maximums are would help reconcile the theoretical with the actual. Then I take that to the track.

You mention better time slips locked up. I'll ask, rather than digging through your thread, what gear at the top end? Do you engage the lockup manually or is it built in at the shift as my OD shift is? (4th gear apply automatically locks the converter unless disabled by my toggle switch).
Interesting thing about my discussions with Andre. One of his selling features was the efficiency he says are built into his converters. More MPH I believe was his promise. That said, it suggests less benefit to locking up than not.
If I hit my stretch goals, I'd be 6000 RPM in 3rd with about 5% slip. 26" tire at 118. That is a stretch though. Good air, with its current exhaust and intake might see 112-113. I'd be happy to work with that. It's the exhaust that's crippling. And a 3000' DA doesn't help either. The very last pass I made (coming on 10 years ago) had a 4 MPH correction to sea level. That's a substantial swing. Considering I've raced at a sea level DA, I understand the impact it has.

June 5 2015
2210’ (elv.), 59F°/15C°, 29.91” Hg/101.29 kPa, 51% rh
DA: 2855

12.92 @ 104.87, 8.21 @ 83.77, 1.85 60’
12.479 @ 108.653 MPH (corrected)

12.93 @ 105.46, 8.23 @ 83.15, 1.85 60’
12.489 @ 109.264 MPH (corrected)

Aging tires (hence the 60') and an aging engine. Not much of a converter either. But the MPH was encouraging. By the way, those corrected numbers closely match my PB's back in the sea level days (or below sea level on the best days!).

 

I know others here have done the WOT / 3rd gear / lockup on the dyno. I wonder if any of them were forced into a rebuild as a result?

 

You are right, I agree on that.


 

I've locked up in 3rd (at the request of the tuner) for every dyno pull. Maybe 15 in total, most at WOT shortly after it shifts into 3rd.

I'm running a single disc Edge converter. Not to say that I won't, but haven't had any issues so far.

 

Interesting.
Is this to say that you manually shift to 3rd, engage to clutch and then pin it? I'm guessing that you a manual on/off switch?

 

Correct- shift up to third, lock converter, get into it gradual enough to prevent a downshift, then WOT.

Yes, I have a manual lockup switch (not ideal but don't have the factory ECU anymore and no speed input to the aftermarket one).

 

That would be the way I'd go about if I find the guts to do it! I'll tell you though that's there's been such a litany of broken parts prior to this combination, that if I break something else, I just might pack it in!
I've got the TCC wired the non-computerized OEM way with vacuum and brake switches. There's also the 4th gear applied switch. In addition to that I've incorporated an auto / off / manual toggle for more control over the function.

 

I don't know. I do it but hard to say that it's worth the risk. Especially if it'll kill your hobby

You remove a variable, which appeals to a tuner. Otherwise it's like dropping the exhaust and air filter for a hero run. You get to say the car made X horsepower, but it still isn't going to matter in how it performs in the real world.

 

Visiting a chassis dyno would be more about gathering some information rather than tuning. I tend to have things pretty well sorted before I get there so it's more a matter of validation. Besides, leaning over the fender and working on the carb and old school distributor are time consuming and dyno time can be expensive. And I'd rather not pay a tuner to do that (that is if there are any left that work on the old stuff). In the past, I've developed the tune at the dragstrip and to some extent on the street and the dyno shows me peaks and relative TQ and HP. It's difficult to say what the engine actually puts out with the data derived from a chassis dyno. Not to mention the differences in the dynos themselves.

As for a hero run, that too will be track based. In as much as it would be a real A to B comparison with the exhaust in place vs the collectors open on the rollers, dropping the exhaust and adding the extensions would probably prove problematic. If I were to think about the overall picture, electric cutouts would be the way to go. Then that comparison would be easy. But that's a ways off right now.

 

I hear ya. Dyno is all for WOT tuning for me. I like that it's controlled and safer than the street. Part throttle and drivability I can handle on the street.

Yeah, where it should be.