Silverado 1500---5.3 L Tow package

[DieselDrax]

Originally Posted by MR.M

I have yet to come across an electronically controlled torque converter . one that will lock up by electronic controls . every torque converter I've come across has a preset lock-up set at a specific rpm . you can order torque converters that lock-up at different rpms . racers use them

You are confusing torque converter stall speed and TCC (torque converter clutch) lock-up. Two entirely different things, stall speed is determined by the design of the torque converter itself whereas TCC lock-up is 100% electronically controlled on every single electronically-controlled transmission made.

Stall speed is something racers want just right as it will allow them to either use a transbrake or the vehicle's brakes to hold the vehicle in place in gear while applying throttle to get the engine near peak torque so you achieve a better launch.

TCC lock-up programming varies by manufacturer and vehicle, but in most trucks the TCC lock-up happens around 3rd gear and is easy to tell when it happens as the engine RPMs only drop a little compared to a gear change. Once the TCC is locked most programming does not unlock it until back in the lower gears. For example, my transmission locks the TCC just after shifting to 3rd gear and keeps it locked in 3rd through 6th gear. Locking the TCC reduces heat in the trans since the torque converter is no longer slipping (fluid slippage = heat).

Some programming will unlock the TCC with light increases in throttle rather than doing a full gear change, other programming keeps the TCC locked in the higher gears and will downshift instead of unlock the TCC when more RPMs/power are called for.

TH programming does vary for sure. Some increases line pressure for firmer shifts to reduce clutch slippage (and reduce heat), some holds RPMs longer between shifts to help prevent lugging the engine and causing it to fall out of the power band, some do lock out one of the OD gears, etc. Best way to try and figure out what it does is to a) read the manual and/or b) experiment and see what changes with it on vs off.

[AlaskaErik]

I have a 5.3 Silverado. The owner's manual states tow/haul mode is most effective when your total weight is at least 75% of GCWR. My GCWR is 15,000 lbs, so I use tow/haul whenever I weigh 11,250 or more. No other criteria is considered. If I don't know my exact weight and I'm close to 11,250, I'll err on the side of caution and use tow/haul, as there is no harm is using it below the 75% threshold.

[MR.M]

Originally Posted by DieselDrax

You are confusing torque converter stall speed and TCC (torque converter clutch) lock-up. Two entirely different things, stall speed is determined by the design of the torque converter itself whereas TCC lock-up is 100% electronically controlled on every single electronically-controlled transmission made.

Stall speed is something racers want just right as it will allow them to either use a transbrake or the vehicle's brakes to hold the vehicle in place in gear while applying throttle to get the engine near peak torque so you achieve a better launch.

TCC lock-up programming varies by manufacturer and vehicle, but in most trucks the TCC lock-up happens around 3rd gear and is easy to tell when it happens as the engine RPMs only drop a little compared to a gear change. Once the TCC is locked most programming does not unlock it until back in the lower gears. For example, my transmission locks the TCC just after shifting to 3rd gear and keeps it locked in 3rd through 6th gear. Locking the TCC reduces heat in the trans since the torque converter is no longer slipping (fluid slippage = heat).

Some programming will unlock the TCC with light increases in throttle rather than doing a full gear change, other programming keeps the TCC locked in the higher gears and will downshift instead of unlock the TCC when more RPMs/power are called for.

TH programming does vary for sure. Some increases line pressure for firmer shifts to reduce clutch slippage (and reduce heat), some holds RPMs longer between shifts to help prevent lugging the engine and causing it to fall out of the power band, some do lock out one of the OD gears, etc. Best way to try and figure out what it does is to a) read the manual and/or b) experiment and see what changes with it on vs off.

Thank for the clarification of the two differences on stall and lock up . i had always thought lock up was also rpm related.

[davez]

After reviewing the replies, I decided to use Tow mode for the 8000. lb trailer; especially since the mileage won't increase much and I prefer not to invest in another transmission for the 2014 Silverado 5.4L. Thanks to all

[007matman]

Biggest thing you can do to save the tranny is put in a larger cooler like the Tru-Cool 40k. It's surprisingly easy to do.

Originally Posted by davez

After reviewing the replies, I decided to use Tow mode for the 8000. lb trailer; especially since the mileage won't increase much and I prefer not to invest in another transmission for the 2014 Silverado 5.4L. Thanks to all

[kamper00]

Probable comparing apples to bananas, but a few years back towed our old RV from CT to FL and back with a Mountaineer 5.0L. (RV weighed appox 5500#)

Monitoring the engine vitals on the way to and from, I found coolant and transmission temps to be notably lower using OD.

As long as it didn't hunt between OD and D I left OD on.

..this result is not what I expected.

My old truck 05 F250 V10, I used tow/haul as needed as it did also downshift when going downhill, as well as held the gear longer, I don't recall it locking out OD.

Tow/Haul might be more beneficial in modern trucks as the newer engines need to rev with their OHC than their predecessors OHV's

[PenJoe]

I have been experimenting with our tow/haul. At first I couldn't notice the difference, now I can. Truck only, 16-21 MPG, towing a 5'X 12' flatbed trailer with perforated drop down gate drops the mileage to about 9-13 MPG, about the same as pulling a 19' boat.

We tow approx 7,000 lbs with a 2013 Silverado 1500. Pulling 7,000 lbs is one thing. Pulling 7,000 lbs and dragging an 8'x9' wall is another story. We get 8-9 MPG towing most of the time. Wind resistance is a major factor because the cargo trailer empty or full gets us about the same gas mileage.

We are pretty firm believers in using tow/haul no matter which trailer we are pulling. Going down a grade, it does much better at holding down the speed gain, and it incorporates downhill braking. Maybe the grades here don't cause over reving. As for gas mileage suffering with added revs on a decline, the fuel management is not feeding added fuel. It is using the compression to hold the speed down.