torque converter not locking up.

i've got an 02 chevy 2500hd 6.0L with a 4l80e transmission, for the past few days my torque converter hasn't been locking up.

and i'm curious what could cause this? besides a bad converter in general.

What really makes it tough is that you just had it out of the truck and rebuilt it, so that can open up a billion more chances of failure.

I'd check the simple stuff first, loose wire connections, fluid level, etc. Best would be to take it to someone with a scanner that can watch the parameters as the truck is driven and see what the computer is being told, which will tell you why it's not locking the convertor.

My 92 also uses a 4L80E, and had convertor lockup issues. It was originally my grandfather's truck, he took it in twice, they just changed fluid and said they could find no problem. After some searches, some posts were everyone told me it was going to gernade at any second, rebuild now, etc etc, I came across something actually helpful. The brake light switch also is linked to the trans, touching the brake pedal will unlock the convertor. And it's a seperate connection or "leg" inside the switch assembly, so this happens with much less pedal travel than it takes to make the brake lights come on. No amount of adjustment or pulling up on the brake pedal made a difference, so everyone assured me that wasn't the issue. I tore the switch apart and found that the connections were worn away to nothing, the small tab was litterally 80% gone. New switch, no more convertor issues in well over a year and 20,000 miles.

thanks! i kind of figured it was a sign of it about to go out which would blow, big time! with the brake thing you had no problems with the brake lights working?

oh! and i had an ocasional small slippage in it for maybe the first hundred miles, i'm assuming it was just the air bubbles working their way out, any ideas what that could be?

My brake lights worked fine.

Slippage for a few hundred miles? No bueno. I'd get someone with a scanner to see what your trans/computer is trying to tell you.

That's why I have always been a traditionalist driver ---- the cock-and-bolt simplicity of manual trans, and the total control a driver can have in ascents and in mountainous descents where a reasonable amount of engine-braking is important and sizeably beneficial in terms of safety. But that's just me gentlemen....

Those torque converters even meter down the power getting onto the wheels. That's why when you subject an auto-trans vehicle in a chassis-dyno, it is the characteristic of the torque converter that is read by the dynamometer, where wheel-hp and torque is lesser than the one you get from a manul-transmission.

adam it was only for about the first hundred (probably about 60-75 miles) and it's completely stopped now, when we get some decent warm out in the next couple days i'll look at the brake switch.

and in all honesty i'd like a manual, but for intown driving i'd find it annoying and veerrrry agravating at times.

adam it was only for about the first hundred (probably about 60-75 miles) and it's completely stopped now, when we get some decent warm out in the next couple days i'll look at the brake switch.

and in all honesty i'd like a manual, but for intown driving i'd find it annoying and veerrrry agravating at times.

I had the same thing happen to my chevy in high school. I had a few trans shops look at it and they all just wanted to power flush it. Finally some random shop told me to replace that switch. I think it cost me around 10 dollars and 5 minutes of my time but I never had a problem again.

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