Question for the GN Guys

[Don B.]

A friend told me that you could install a switch

to get the torgue converter to lockup.

He said that it basicaly it grounded the connector

on the trans.

Could one of you GN drag racers tell me what wires

that would be?

[2seater]

I don't remember what year your Reatta is, but my '90 manual indicates the tan/black wire, #422 is grounded by the ECM for lockup to engage. Grounding that wire should lockup the converter at any time. I know some of the GN guys do this in high gear and it helps trap speed.

[Don B.]

Thanks Hal. I'll give it a shot this weekend.

I hope it brings my 1/4 mile times down.

[2seater]

Do you drag race your Reatta? What sort of mods and times do you have? I don't know how long the clutches in the converter will last, but we have a lot less power and especially torque than the GN's.

[NTX5467]

GM played the lockup converter actuation "game" differently on some applications than others. There are also pressure switches on the trans valve body which also modulate when the coverter will be allowed to lockup, but might not due to manifold vacuum conditions or throttle position input. Once you find the connector on the side of the trans, there can be one or more wires in it. Only one will energize the internal wiring for the lockup as it will connect to the pressure switches (which are in series with the Transmission Converter Control (TCC) solenoid (which is the last link in the electrical chain) internally.

The first few years of the lockup converters, they tried to orchestrate the lockup at about 30mph or so. Lots of customer complaints about perceived "misses" that were not due to an engine miss. Later ones went for closer to 45mph, which worked better, and had better "apply" modulation (meaning more slip when they locked up). Full electronic controls made things work much smooooother, but might interfere with WOT lockup unless the computer is rechipped/programmed.

A typical lockup converter electrical circuit would include a vacuum switch, brake switch, pressure switches inside the trans, and the converter solenoid. If there is also input from the throttle position sensor, that would be a modulating factor too (for the ECM).

Only GM factory application transmissions that I know of that would keep the converter locked up at WOT were the Camaro Z/28, Corvette, and police car applications (on the THM700, typically). I understand this was a valve body issue.

Interestingly, when Chrysler did their development work on lockup converters, they used drag racing applications to do it, but never offered a lockup converter transmission on any heavy duty application. Their lockups were modulated only by fluid pressure, though, and lacked a little of the finesse of the GM transmissions in that respect. Some of the converters were also known to break the input shaft splines (in the converter and/or in the trans) if the metal hardness was not to spec.

I'm not sure what ET time comparisons might exist for the racers who lock up the converter in high gear, but it might not be quite as much of a benefit as you might expect. Try it and see . . .

Just some thoughts,

NTX5467

[Guest]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Only GM factory application transmissions that I know of that would keep the converter locked up at WOT were the Camaro Z/28, Corvette, and police car applications (on the THM700, typically). I understand this was a valve body issue. </div></div>

The '82 Turbo Regal had WOT lock up, but it was droppped mid-year after costumer complaints. The was a TSB for changing the PROM to a non-WOT lock up chip.