[Jdmsw20]

I have 15' 5.7l. I haul cars to the drag strip a couple times a year. Now that the major highways where I live are 70mph now. The trailer plus car I haul I would safely say around 5k pound total. I'm new to towing as this is my first truck so forgive me if I did/say something dumb. I would put the truck in cruise at 75mph but then when any slight incline on the road the truck would shift into overdrive or down shift don't know the differnce. Even at 70mph it does it also. But if I go 65mph it barley does it. Question is am I hurting the truck but doing so?

 

[Nm6300'asl]

It is unlocking the tourque convertor, allowing it to slip which can cause high trans temps. Not good for longevity of the trans. Use the tow-haul button and if it is hilly terrain use s mode and manually shift staying in 4th or 5th gear. Slow down a bit, no need to tow @ 70 or above, most trailer tires arent rated for it.

 

[Blenton]

Most wouldn't advise using cruise control while towing. You are piloting the vehicle, not the computer - it just controls how much fuel gets dumped in to the motor, when it blows up, and what gear your transmission is in - so when you put it in cruise control, you let the computer try and guess what the road is doing, then react to the varying road conditions. The cruise control on these trucks tries to keep a very tight leash on the speed and not vary a whole lot; my truck only lets the speed drop by maybe 2 MPH before it really gets in to it to push me back up to speed by using more throttle or downshifting. When towing, there's a lot more weight to move around, so the truck is even more aggressive and either dumps more fuel or down shifts (usually the latter), as those are the only two options the computer has to get more power.

IMO, when pulling a trailer, you should be proactive about reading the road and feeding input to the truck via the throttle. Theres a hill coming up? Feed the throttle a little before before you get there to get a little momentum. There's a downhill descent coming up? Let off the throttle, then give the brakes a firm application as you begin to descend (the computer sees this and shifts down a gear or two to help engine brake the vehicle). You slowed down a mile or two an hour because of a small grade in the road? No big deal. Feed it a little more throttle and give it a second to get back up to speed. You're slowing down pretty quickly because of a steep hill? Stab the throttle quickly and the computer reads that as "downshift now!" and it will pop down a gear or two.

What @Nm6300'asl said is good advice. The "small" downshifts are the converter unlocking which can raise trans temps. Use Tow/Haul mode and/or manually keep it in 5th by shifting to 'S' on the shifter and select '5" (you can shift from D to S while driving without issue, but note that it usually shifts to 4th gear when going from D to S). The RPM's are up a little bit but if you are keeping it around 70-75 MPH they are still fairly low and will prevent a lot of the downshifting.

 

[Jdmsw20]

Never thought about putting in S mode to keep it in single gear. That's a really clever idea. I'll try that out on my next trip. I try not to use cruise control on short drives but then for the long ones 3+ hours I need to use it.

 

[Thumperpaul]

Sorry to hijack the thread, but it is ok to tow using 5th gear? I have just been using Tow/haul and keeping it in 4th...

 

[koditten]

If you adhere to the law and stay at 65 mph, 5th is too tall of a gear. I use 4th and the truck runs perfectly. I'm around 2600 rpm's and the truck is not laboring at all and there is little stress on the transmission.

 

[Thumperpaul]

If you adhere to the law and stay at 65 mph, 5th is too tall of a gear. I use 4th and the truck runs perfectly. I'm around 2600 rpm's and the truck is not laboring at all and there is little stress on the transmission.

That’s kind of what I thought, although I will pop it into 5th if I am on a long, flat stretch of highway.

 

[Powertechn2]

I haven't towed much over 5k lbs.

But when using tow/haul, and locking it in 5th manual mode (just limits the up shifts, 5th and 6th really are just essentiallyboth overdrives), had no issues.

Michigan is hilly as all get out.

 

[koditten]

I haven't towed much over 5k lbs.

But when using tow/haul, and locking it in 5th manual mode (just limits the up shifts, 5th and 6th really are just essentiallyboth overdrives), had no issues.

Michigan is hilly as all get out.

Not the middle of the state. We are stupid flat around here.

 

[Powertechn2]

Not the middle of the state. We are stupid flat around here.

Lucky. Here it is hilly af.


Like I don't mind flatter girls or flatter ground. But I am stuck with hills and crazy b's.

If I head to Black Lake, it is just essentially a giant hill up I-75 till I hit M-33, which is still hills, but more fun, like roller coaster hills at one point. I stopped taking I-75 to exit 310 as the M-33 route actually gets better mpg with the lower speed. On I-75 you hit a point called something like 3 mile hill, and funny thing is it is an incline before, during, and after.