TCC lockup switch

Raptordude · January 30, 2017

Hey guys, I have an 01 2500HD, gas 6.0, with an untouched 4l80e tranny.

The tranny shifts great, but I like manual transmissions. I like to have control.

Got me thinking, is there a wire you can put on a switch to control when the torque converter goes into lockup?

It would be nice to have it off while climbing hills, and have it on in lower gears when pulling loads.

It may take 2 separate switches, but I would want one switch that when off, the tranny would act like stock. When on, it would lock up the converter no matter what gear I'm in.

I would like a separate switch that when it's on, it would act as stock, and when off, it will unlock the converter.

Has anyone done this?

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Formulabruce · January 30, 2017

Gm does NOT recommend using it during Towing, , and will NOT lock in any gear aside from 4th. A Trans can be modified to do it ( my '89TTA TH2004R does it stock, Locks in 3rd and 4th, but this is very rare)

Also, you already have the switch, its on the end of your shifter. . That shuts off the lock up.... Tow mode... Got a little light on dash too .

The 4L80E got some nice upgrades in '04, but I wouldnt play with yours if it works well, keep it cool, and be happy. Good luck

Raptordude · January 30, 2017

Ok sounds good, thanks for the info

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GM-Lifer · February 4, 2017

When towing through the hilly terrain in Missouri I put the tranny selector in 3rd gear. That eliminates a whole bunch of the shifting it would do otherwise. Your just kidding yourself if you expect to use overdrive while pulling a load.

davester · February 4, 2017

Gm does NOT recommend using it during Towing, , and will NOT lock in any gear aside from 4th. A Trans can be modified to do it ( my '89TTA TH2004R does it stock, Locks in 3rd and 4th, but this is very rare)

Also, you already have the switch, its on the end of your shifter. . That shuts off the lock up.... Tow mode... Got a little light on dash too .

The 4L80E got some nice upgrades in '04, but I wouldnt play with yours if it works well, keep it cool, and be happy. Good luck

On my '04 Sierra, albeit with a TransgoJr HD2 kit in it, does lock up in 3rd occasionally, when it downshifts from 4th to 3rd going uphill at about 60 mph, at least as ported by my Insight CTS2. The HD2 kit shouldn't be causing it, as the lockup is computer controlled.

Raptordude · February 4, 2017

What does the 3rd gear selector do? I understand it keeps it from going into 4th gear and supposedly keeps it from going into lockup. But as davestar said, it seems to go into lockup in 3rd sometime. If you're in D and the tranny is in 3rd, if you select "3" you can hear something engage/disengage but rpm does not change

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Formulabruce · February 4, 2017

On my '04 Sierra, albeit with a TransgoJr HD2 kit in it, does lock up in 3rd occasionally, when it downshifts from 4th to 3rd going uphill at about 60 mph, at least as ported by my Insight CTS2. The HD2 kit shouldn't be causing it, as the lockup is computer controlled.

Over 60 and a less than 30% load can do it, but it doesnt usually hold and its not good for the transmission to repeat that scenario a lot. 3rd is a 1:1 ratio

Formulabruce · February 4, 2017

What does the 3rd gear selector do? I understand it keeps it from going into 4th gear and supposedly keeps it from going into lockup. But as davestar said, it seems to go into lockup in 3rd sometime. If you're in D and the tranny is in 3rd, if you select "3" you can hear something engage/disengage but rpm does not change

Lock up in 3rd only happens when selector is in Drive, and in rare low torque load conditions with a slight load applied and over 60... why fuss of if? The 4L80 is NOT designed to do it because Lock up mechanism is weak compared to the transmission.

The only reason the 2004R had a 3rd and 4th ( .67) lock up was due to it being a light car, and the need to do an easy 160 mph.. as a Indy pace car.

davester · February 5, 2017

What about the torque converter locking up in 3rd gear is not good for the transmission?

GM-Lifer · February 6, 2017

The torque convertor shouldn’t lock up in third gear, but I know some vehicles are programed different than others. Try running around in third gear without a load on the truck and watch your tach & listen. The torque convertor is most apt to lock under light engine loads. If it does lock then, you’ll know for sure.

It depends on the terrain, but in my experience you’re tranny is going to do a whole lot more shifting up and down if you try to use overdrive. I’ve spent many hours pulling trailers on the interstate in 3^rd gear and haven’t seen one indication of it hurting a thing.

FYI - When I first bought my ‘05 Silverado with 95,000 miles, the torque convertor would not stay locked in until I got over 60 mph. At a constant 50 mph you could see the tach go up and down as the TC locked and unlocked. My brother-in-law fixed this problem by shimming the springs on the valve that controls TC lock-up with a couple 1/4 inch ball bearings. Evidently it’s a common problem with the 4L60 transmissions. Sure was a bunch cheaper than what a shop would have charged me to rebuild the transmission!

Raptordude · February 6, 2017

Yes 3rd is designed to haul heavy. If you're pulling a big trailer, you don't want to go over 3rd gear.

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Firestone · March 7, 2018

I would like the Torque converter to stay locked in more on my 03' Suburban with an 8.1L and the 4L85. Maybe if shimming the spring helped to keep it from switching so much on the 4L60 it could help on the 4L85. Just a small amount of throttle kicks it out of lockup and it rather annoying. The Burb has a .410 rearend and 4th gear lockup is really where you want to stay in most non-towing conditions to help with fuel mileage.

Raptordude · March 7, 2018

I would like the Torque converter to stay locked in more on my 03' Suburban with an 8.1L and the 4L85. Maybe if shimming the spring helped to keep it from switching so much on the 4L60 it could help on the 4L85. Just a small amount of throttle kicks it out of lockup and it rather annoying. The Burb has a .410 rearend and 4th gear lockup is really where you want to stay in most non-towing conditions to help with fuel mileage.

My truck did the same annoying thing. Custom tuning with EFI live can get it to lock in the way you want

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