I've been thinking of wiring a circuit so my converter can't lock-up during a full throttle pass on the 1/4 mile. I believe the ECM locks the converter at around 7X MPH regaurdless of throttle position and raising that MPH limit in the PROM hasn't worked. I think converter companies like vigilante recommend against full throttle lock-up conditions unless you buy their $$$ converters.

Is it a good idea to have a switch to prevent my converter from locking up at full throttle while at the drag strip?

Uh......don't people usually wire a TCC switch to lock-up EARLIER during a 1/4 mile run??

In my opinion, yes. Stock converters and most aftermarket converters aren't made for that and will fail.

I don't think a standard 700R4 locks at full throttle. That's why people put a switch on it to gain a few mph in the traps. AFAIK lockup only occurs at cruise. If you touch the brakes or floor the throttle it unlocks.

My post was in response to this on the PROM board:

https://www.thirdgen.org/techbb2/sho...threadid=38546

I'm just getting my car prepared to take to the track so I can finally get a timeslip. Since this is my daily driver I'm just trying doing preventative maintenance and trying to limit possible problems and breakages by addressing some remaining concerns.

The torque converter will not lock up at the drags (full throttle) unless you go over 6,000 rpm in 3rd gear, I have never seen this happen?! If it does happen to you (at WOT) then you will need to solve/address it.

Not true.

My tranny locks up in 3rd gear going down the track, and locks up on the dyno also.

A friend's 88 IROC locks up also.

It's in the prom.

89gta383 is right on this one. The stock PROM for an 89 Formula 350 does lock the TC at WOT at around 75 MPH. I never felt it till the Vigilante replaced the stock TC. It was not noticeable stock but felt like another gear change with the Vigilante.

Mine locks up in third at WOT as well and stays locked through forth at the drags as verified by my scanner.

Nothing in my GM literature says this should happen, why it is happening to you three I don't know. I'm not sure on what to address, but I would not let this happen as it will gradually destroy the clutch in the TC.

Dana, I was surprised about this too and so was Paul at TransGo. According to all of the Gm stuff I have it is impossible but I have seen it myself.

I would suggest putting a switch in line with the 'D' terminal and disable L/U in this manner when you are going racing as it would be hard on a stock typw converer clutch.

Besides dropping a few hundred rpm's going down the track, why is this a problem on a modified tranny and aftermarket converter?

I thought that lockup reduces some slippage in the convertor. The buick guys sometimes run manual lockup switches to lock the converter going down the track, so this is nothing new.

By the way, I'm using a pro-built tranny and a continental 2400 12" convertor, and will be switching to a yank ST3500 soon, and the current combo has numerous runs down the track with no problems.

I swear it's in the chip.

It is in the PROM. The good thing is it gives higher rear wheel HP readings on a chassis dyno. I don't feel the stock TC or single disk Vigilante is really designed for WOT lockup.

When I had a Z Industries chip I had Ron Zimmer program it to remove WOT lockup all together. Now that I burn my own the problem is back. I've yet to figure out what to change to make it go away.

My converter seems to lockup at WOT at the drags.
According to my finishline RPM and speed, I have 0 slippage
at 104mph so the converter must be locked up.
I do have a switch wired inline in the lockup power lead to the trans
to "lockout" converter lockup but I never tried it unlocked
to see if it makes a difference. I don't use a vacuum switch
like the stock cars did. Wether you will harm the converter clutch
by locking it up @ wot, really depends on the amount of power you have. Mind seems to be fine so far. Art Carr says it will make your car run a little faster in the quarter, but may shorten the life of the converter clutch.