Does the torque converter lock up in third gear ?

[cottonpicker14]

I have several questions

1. I disconnected the speedometer at the tranny and the engine light came on which I expected, but the torque converter did not lock up when it went into fourth gear. I couldnt tell if it locked up in third or not. Does anyone know if 4th gear is the only gear the torque converter locks up in ?

2. By leaving the speed sensor disconnected at the tranny, what damage could I go trying the car around if the torque converter doesnt lock up.

[chargedtt]

if it is programed into the chip it will

[zebra78]

I have heard that the constant slipping at highway speeds can cause excessive heat increases in the transmission fluid, which can lead to transmission failure. I'd be sure the transmission locked in 4th, or was internally modified to use a non-lockup converter; you need a different converter in this case as well.

[ULYCYC]

The ecm needs the information from the trans to operate correct. It's best to hook it back up. No there is no 3rd lockup unless you program the chip to do it or you have a manual control switch.

[cottonpicker14]

One more question then.
Since you say that the torque converter does not lock up in third, if I leave the speedometer cable off, put the shifter in the second D which does not use the overdrive and stays in third and drive locally up to 40mph, will that cause damage or over heat the tranny ?

[Steve V]

Yes,it will damage the tranny. Hook it up or remove it and have the pump modded for non LU. Why don't you want a speedo?

[King_V]

Originally Posted by ULYCYC

No there is no 3rd lockup unless you program the chip to do it or you have a manual control switch.

Um, just want to confirm, in a stock setup, are you SURE about this?

Every GM 200-4R I've driven locked up in 3rd, as well as the 700-R4 and several 440-T4 trannys.

Of course, unfortunately, I've NEVER driven a turbo Buick, so there you have it, but I thought all GM ECMs would lock in 3rd as it determined it needed.

The only oddball I ever noticed is that the T-type LeSabre locked it's 440-T4 in 3rd noticeably later than did the standard vehicles, pretty much at the point where it was just about to shift into 4th anyway... maybe this is how the turbo-V6 cars work as well?


Disclaimer: I'm no expert by any stretch of the imagination, so take that with a grain of salt...

[ULYCYC]

You are correct.. I meant if it had no ecm. On a normal correct setup it will lock in 3rd or OD. Sorry for the confusion