Locking converter in 2nd gear...

[LS1_Dragster]

If you have a really loose converter can you lock the converter in 2nd gear?

Will it unlock for the shift?

Being you cannot feel it shift at normal driving would it hurt to have it locked during the 2-3 shift at light throttle?

Lee

[LS1_Dragster]

Nobody? Someone has to of locked the converter in 2nd!

[joecar]

There's a table to apply the TCC in 2nd gear, see D1001 (you have to make sure D1004 is below D1001).

D2801 can be set to allow the TCC to stay applied during an upshift... altho, I'm not sure if this parameter works on all trans calibrations.

Keeping TCC applied during upshift:
if engine is making sufficient torque then the TCC damper springs may break (see item (C) in attachment)... or the TCC may slip during the upshift (it is only "half" a clutch and so doesn't "clamp" like a "sandwich" as in a manual trans clutch).

Typically a double or triple plate TCC will allow slip-free upshifts with TCC applied since the extra friction/steel plate "sandwich" is able to "clamp" tight... 2P/3P clutches don't necessarily have the damper springs.

Edit: oops, I forgot to attach attachment...

[LS1_Dragster]

This is why I was wondering if the loose 4000RPM stall converter could take it. Right now you cannot feel the shift unless your foots in it. Even though the converter is cushioning the shift does the clutch in the converter still take a hard hit? Does that make sense?

Lee

[Mr. P.]

What transmission?

Yes you can tailor converter clutch state in each gear. Separately, you can instruct the tune to also leave the converter locked during shifts.

Is it hard on the converter clutch? Hell yes. You better have a converter clutch rated for this kind of abuse, like a multiple-disc lockup clutch.

But the real worry is not the converter but the transmission - the issue is leaving the TCC locked during the shift, it hits SO HARD that with any kind of power you risk destroying the transmission input drum and/or other hard parts.

Mr. P.

[LS1_Dragster]

It's a 4L80E.

So it would still hit too hard with the high stall...

But what about just locking it in 2nd and let it release for the shift?

[Mr. P.]

It's a 4L80E.

So it would still hit too hard with the high stall...

But what about just locking it in 2nd and let it release for the shift?

When the lockup clutch is engaged there is no "stall" - the front half of the converter is physically locked to the rear-half. If you want to demonstrate this to yourself, take EFILive bidirectional menu, roll-out in 1st gear & lock the TCC, then moderately accellerate to about 20-mph and feel just how hard it hammers into 2nd under lockup Being a lightweight dragster and 80E the car actually *might* get away with shifting while locked-up, I will have to ask our transmission expert what he would do to an 80E to hold up to this but I am thinking with that trans it can be done in your application. I am going to say from certain experience a 4L60 won't take that sh!t for long lol, you will fracture the input drum even if it is 'reinforced' - now if someone were ever to make a billet input drum for the 700/4L60 that would be an entirely different story . For track use you SHOULD be running with the converter in lockup whenever possible. What we do on the trucks, is to make repeated runs lowering the lockup engage MPH until the fastest time/performance is achieved per each gear. Typically (in heavy trucks) we benefit from TCC lockup in 4th, 3rd, and upper part of 2nd, some of the stock trucks loose E.T. attempting to lockup in 2nd (they don't have enough torque to take advantage) so a little trial/error is expected. For street use we keep the TCC lockup point 5+ mph higher than the shift point, but on a track-specific vehicle you might be able to get more ET gain by locking-up the TCC even quicker than that.

Mr. P.

[LS1_Dragster]

It's not for the dragster it's for the firebird. It's a pain sometimes driving because the RPM's are screaming at 2500 and the cars going 5MPH! Hughes just built the converter too loose, I'm sending it back for a re-stall but not until the car is parked for the winter so in the mean time I was looking for a short term solution....

[MyM8V8]

now if someone were ever to make a billet input drum for the 700/4L60 that would be an entirely different story .
Mr. P.

So where would we be able to get such an item???

[Mr. P.]

Nobody makes an aftermarket drum for the 4L60. :( We are considering lathing one out of 4340 billet, but it will take a ton of time (like a straight week of milling) because the cutting tools have to reach so deep into the drum and still meet extremely close tolerances. We think we can do it, we'll see.

Mr. P.