4L60 towing in overdrive

[archer000001]

Greetings,

 

I had a chance to test drive a GMT900 Silverado recently with the 4L60 transmission, and noticed that when engaging the Tow/Haul mode, the transmission still utilized 4th gear (OD). My question relates to towing a heavy trailer --

 

Is there any way to avoid using OD to keep transmission temperatures down? Other trucks I've owned (non-GM) see rapidly rising temperatures in OD if I forget to engage tow/haul mode, for either of two reasons:

 

- The torque converter clutch doesn't engage in OD gear (does the 4L60?)

- The transmission fluid pump is not running fast enough (driven by engine RPM) to circulate enough fluid to keep temperatures down

 

Thanks!

[pm26]

On my 06 Z71 with the 4L60E transmission, when I engage the tow/haul mode, the truck will not shift into overdrive until you reach speeds of about 70 MPH. If you were towing a heavy trailer, you would probably never get to that speed to begin with. I would just tow in the 3rd gear to be safe.

[GM-Tech]

Put it in tow/haul mode and tow away.

 

Nothing changes in tow/haul in terms of the gears it goes into or the TCC being applied, which IS applied in overdrive. Tow/haul increases line pressure and changes the shifting characteristics.

 

If you want to prevent OD when towing, then just pull down the shift lever one notch. I don't see a need to do this since GM designed this to tow at it's maximum capacity but hey, it's your truck.

[C & A s Dad]

Jim, I will tell you what I do with mine while towing. Even though I am not anywhere near my max tow wt of 8400 lbs, when I am towing my 6500 lb camper, I tow in drive instead of OD. I am almost always towing on 2 lane roads with speed limits of 55 or less. This keeps my 5.3L runnining in it's sweet spot. If I allow it, it will shift into OD at these speeds but will not maintain the speed if I come to a hill. If I am on the Interstate and wanted to tow at 70 + MPH, I can easily run in OD and it will maintain the speeds with no problems because again, I am in the sweet spot. However, I do not tow at 70 + and for safety sake, I keep it under 60.

[Frank Sub]

Hi archer000001--My towing experience with a 27' Airstream, 6400lbs on the double axles, mirrors C & A s Dad. I always tow in 3rd, and with the 5.3ltr, and a 4.10 rear, 65mph is 3000rpm, which is just where I want to be for almost max torque, and best overall handling. If you try to tow in 4th at highway speeds, your transmission will struggle a bit at the slightest grade, and then down shift into 3rd.--Frank Sub

[TEE]

I agree...I think as long as your less than 3K...should be OK in OD on flat land only. Even though I'm only towing 2K..I take it out of OD on hills and two lanes where I'm not above 60 MPH.

Just a cents worth....