tcc unlock prevention threshold
stock is set for 88mph
if i set this for 55mph, will i be certain the tcc will always be locked above 55mph? this would be good for hwy and gas milage correct?
and i hear for racing people like to permanently lock it, could i possibly run a second chip with that constant set to 1mph?

 

The clutch in the stock TC supposedly won't last long at full load. I don't *think it can lock up in first, if I recall correctly. You can buy a special converter meant to hold the load of a strong motor, but I think most wouldn't lock it until after the stall speed of the converter.
Just use the lockup closer to stock and you won't be too dissappointed.

 

what do you mean the lockup closer to stock?

im running a b&m 2400 stall if that makes a differnce.

 

Definatly the stock TCC won't last long so for this reason I raise the mph limit to 110mph. At this mph my car has shifted out of 3rd and into 4th (or it would hit rev limiter). If I had full throttle 3-4 upshifting I'd put the manditory lockup to 255mph.
I think you can lockup the tcc in 1st. I don't remember seeing a circuit/switch that doesn't allow it. It would probably stall the engine or just sit there slipping.
As for "most wouldn't lock it until after the stall speed"... seems kind of pointless to lock it up when it's not slipping . The whole idea of a lock-up TC is to lock it up UNDER the stall speed to maximize your part-throttle efficiency .

With more torque than stock at the same throttle position you might want to lower the TPS unlock table by a scale proportional to the the old torque/new torque. So if you're making 400ft-lbs peak now and stock it was like 320ft-lbs then scale the table by 0.8 and see where that leaves you. You shouldn't (so long as your foot isn't made of lead) feel any difference except when you go to accelerate hard the TCC will unlock earlier. Take a look at different stock bins and you'll get an idea of what GM did and maybe come to some conclusions of why they did them. A search would also turn up some answers.

 

what would be wrong with having a mandatory lockup at 55mph when im racing or something? or just street driving?

 

Your B&M unit has basically the same clutch as stock.
The clutch can only hold so much power prior to slipping.
Slipping is bad for numerous reason. One you may not know is that the 700 oil flow is from the converter to the valve body. So all that clutch material you'll generate will go through the VB. And cause other problems.
Not much can be done except to minimize TCC shifting and slip. Making the mandatory lock at a lower mph will be good for your ET etc. but hard on the clutch and trans.
When you start making more power, you can reach the TCC limits sooner. Hence what JP posted above.

It's been a while, but IIRC the forced lock prevents the delta TPS or TPS limit from unlocking the TCC. So stepping on the gas a lot with a 55 mph forced lock would no longer unlock the TCC. But make a lot of power and cause slip.
At least till you reach the TV limit built into your trans VB and downshift occurs.

 

As mentioned above the TCC won't take the WOT abuse. The 700R4 won't lock in 1st gear, no fluid feed to the TCC circuit.

RBob.

 

Nothing... if you don't like your TCC by all means lock it up under WOT and see if it'll last. The tcc is a single plate, not multi in your torque converter. This means it's weak, it's also a small diameter and then there's the fact that it's wet (not dry like a manual trans 3rd gen clutch). In other words, it wasn't designed to handle a lot of torque, just enough for cruising and light acceleration. Nothing like WOT and racing.

 

i thought people made tcc lockup switches they used for racing though.

 

Only those that didn't know how the tcc works or have a built multi pack clutch use those switchs. They aren't ment for stock style tcc's.

 

I went through a transmission on my G20 before I realized that the TCC power was being fed straight through the brake switch, to the 4th gear N.O. switch, straight to ground. When I converted to TBI, I eliminated the original TCC wiring and vacuum switch, then plugged the TBI wiring connector into the transmission. It was locking the TCC, no matter the TPS. Sucked big time for part throttle acceleration on the highway in a 5,300+ lbs Conversion Van with a 350 and a 3.08 gear. Not to mention the abuse killed the TCC friction material. Nice black gunk in the pan. I now have it rewired to work off the ECM and it works much better. I typically hold TCC lockup to about 35% TPS at speed, less at lower speeds. I gradually let it stay locked up longer at speed, since at the higher speeds it reacts better.

 

JPrevost,
I meant if racing, not on the street for this. It would be silly to let it slip all the time on the street, as you said. But, I don't really know how it's used in racing, just throwing out a guess, and I could easily be convinced otherwise if shown a good reason.

 

One problem with locking up the converter on the 700 series of trannies, is that often the lining tends to *shred*. This material then plugs up the cooling lines, and the tranny just cooks....... Maybe that's changed but for years it was an issue.

BTDT, had 4 trannies do that.

Fast forward to today, currently with my 200R4, I have a Yank Pro Stock 10" converter, it's designed to withstand WOT engagements, and continued WOT conditions. I op'd for the HD TCC. It's a serious converter that costs serious money. You're not going to find a $300 converter that acts or lasts like a $900 one.

IMO, you're not sure about the TCC specs of your converter, call the manufacturer.

Not being into drag racing, my forced lock up is set to 115 MPH. Just kinda fun having the car shift *one more time*......