Cruise control in tow/haul mode - Diesel Forum

rthorntontx · 07-10-2008, 08:54 PM

I have searched the forum and did not see an answer to an issue I am running in to.

I pull a 5000lb travel trailer with my ’08 F250. I use tow/haul mode because I figure that is what is best for minimizing wear and tear on the truck as well as maximizing safety. However, when I set the cruise control, the truck seems very sensitive to maintaining the exact speed. For example, when I approach an overpass, the transmission downshifts to maintain the speed, usually 65. In my previous tow vehicle, an Expedition, the speed would drop to 60 or even 55 with the cruise set and then creep back up to 65mph. I would tow with overdrive off with the Expedition.

It seems to me that the ‘hunting’ involved with the cruise set in tow/haul mode defeats the purpose as I understand that transmission hunting is one of the harder things on the transmission.

I have not towed since I’ve read through the forum posts so I have to admit that I have not tried towing without tow/haul.

I guess my question is – is it OK for the transmission to do a lot of hunting as long as it is in tow/haul mode? Or, should I run the truck with tow/haul off until I reach a steep incline/decline? Most of my driving is on the relatively flat gulf coast area.

Thanks.

Robert

DieselDunc · 07-10-2008, 09:54 PM

Robert, I have an 08 F-450 with 4:30 rearend. We pull a 38' fifth wheel that weighs 17,500. I also only use tow/haul mode. I've noticed the same thing about downshifting quite a bit. I'm don't like all the shifting. If you take the cruise of it want shift as much because you can loose more speed to keep it in overdrive. However, I like the cruise so I don't have to worry about my speed. There have been a few times I've taken cruise off, but normally just set it and forget it. My previous truck was a six speed and I could loose ten miles per hour or more and not kick out the cruise. I loved the six speed on the road, but it sure go old in town. Gary

Engine31 · 07-10-2008, 11:25 PM

I run cruise in Tow/Haul pulling my boat, 18 to 19,000lbs,as long as I'm not on a big hill, I find it works nicely if I just accelerate a little faster then the cruise to compensate for the hills.

mattebury · 07-11-2008, 12:09 AM

I pull a 10,000 lb fiver and I've never noticed any problem in cruise control and tow/haul mode. I usually keep the speed around 60 to keep the CHP away.

davydee · 07-11-2008, 10:47 AM

When this occurs on our older truck, I'd just tap the brake to knock off the cruise and then re-engage when the road level out. Do you believe that'd work with the 08+s? Thanks David

marspec · 07-11-2008, 12:42 PM

I use tow/haul whenever towing mainly for the braking effect. My complaint with the tow/haul is that when the truck slows a couple of miles and downshifts it accelerates to the set speed and in some instances a little higher. I imagine more than a few truckers or other drivers who are trying to pass under those circumstances get a little upset when I start accelerating. There ought to be some way for the computer to maintain the speed and then accelerate to the set speed when the boost drops.

DXprowler · 07-11-2008, 02:37 PM

I don't use cruise control very often when towing my 10,000 lbs 5er. It has to be reasonably flat but as soon as the trany starts hunting I'll turn it off! I just don't like the way the trany downshifts and then the engine accelerates in what to me is an chaotic and erratic fashion. Basically, I guess things just don't sound good to me!!

BTW don't use cruise in wet, icy or snowy conditions! If in cruise and the wheels roll over a slippery/icy spot and the vehicle is accelerating, they could spin and put you in the ditch in a nano-second!

Stymie · 07-11-2008, 04:38 PM

the truck downshifting and bringing up RPMS is better for the engine, and the tranny. it will keeps temps down, as opposed to lugging it.

NickBeek · 07-11-2008, 07:12 PM

I had the same problem with my '04 6.0 and TorqueShift. I hated that, especially since I live in the foothills of SC. I just used to foot drive the truck and feather the pedal to keep it in gear. I believed, and still do that the tow haul is there for a reason and used it when ever I was towing. But cruise and tow/haul together just didn't work to my liking so I ditched the cruise when towing.

1970Cyclone · 07-11-2008, 11:05 PM

I pull quite a bit with my truck, (13+K Fiver), I have found it best (especially concerning fuel mileage) NOT to tow with the cruise on if there is ANY type of grades.

You can do a much better job using your foot to control the speed, you can allow the vehicle to gain a little speed going downhill (pretty much for free) and use the extra speed (inertia) to get up the next hill..

I hauled around 200 miles last weekend (100 up, 100 back) on the same route and experimented with the cruise.. Cruise on, 7.5 MPG, cruise off 10 MPG. The cruise on our trucks need to be adjusted a little to give us some wiggle room around the set point. I maintained 55 to 60 MPH with 65 being my absolute upper limit and 50 being my absolute lower limit. It is amazing how much difference an extra 10 MPH makes when starting a grade. You do not have to increase the throttle setting much (depending on the grade of course) if you have increased speed at the bottom and if you allow the truck to bleed off a little speed going up. If I saw it was losing speed too fast, then I went ahead and allowed it to downshift to get er over the top.

If you are towing with the cruise, petal it a little bit going downhill to allow it to gain a little speed for the grades, the cruise will take over when it catches back up. I will guarantee an increase in fuel mileage and a tired ankle when you get home.

Quote:

Originally Posted by rthorntontx

I have searched the forum and did not see an answer to an issue I am running in to.

I pull a 5000lb travel trailer with my ’08 F250. I use tow/haul mode because I figure that is what is best for minimizing wear and tear on the truck as well as maximizing safety. However, when I set the cruise control, the truck seems very sensitive to maintaining the exact speed. For example, when I approach an overpass, the transmission downshifts to maintain the speed, usually 65. In my previous tow vehicle, an Expedition, the speed would drop to 60 or even 55 with the cruise set and then creep back up to 65mph. I would tow with overdrive off with the Expedition.

It seems to me that the ‘hunting’ involved with the cruise set in tow/haul mode defeats the purpose as I understand that transmission hunting is one of the harder things on the transmission.

I have not towed since I’ve read through the forum posts so I have to admit that I have not tried towing without tow/haul.

I guess my question is – is it OK for the transmission to do a lot of hunting as long as it is in tow/haul mode? Or, should I run the truck with tow/haul off until I reach a steep incline/decline? Most of my driving is on the relatively flat gulf coast area.

Thanks.

Robert

SDdriver · 07-15-2008, 02:16 AM

No need to keep the tow/haul on all the time. It just wastes fuel.

I only use the tow/haul in the mountains.

I have the same thing with cruise control. It down shifts on most overpasses.

I noticed when the boost got over 22-23lbs and the RPMS dropped to about 1750 it was getting ready to down shift. I would tap the brakes, let the hill scrub off some speed and then get it back going down the back side.

THis method increased my MPGS. When my wife drives she lets it down shift all the time and she always gets at least 1-2 mpg less then when I drive.

kghenson · 07-18-2008, 12:53 PM

I'm with SD, last time I towed I discovered that in T/H the truck wouldn't go into 5th until I took it of T/H at 60mph. I learned to get MUCH better mileage I did best by tapping cruise a couple of times when dgoing down hill to pick up some free speed and tapping down when climbing to keep it in 5th. I only put it in tow haul when flat or downhill.

Picked up 2-3 mpg with just a little bit of input to cruise. i used to be a set it and forget person, but not at 4.79 a gallon, lol

Stymie · 07-21-2008, 01:43 AM

so what you're all saying is a few mpg is worth the extra strain and heat in the tranny and motor? Have it yourway

kghenson · 07-21-2008, 09:31 AM

Quote:

Originally Posted by Stymie

so what you're all saying is a few mpg is worth the extra strain and heat in the tranny and motor? Have it yourway

Well actually, if you read my post

I am keeping it from shifting, so less strain. as to the motor I'm easy around 1700 to 2000 rpm which is well up on the torque curve.

So no extra heat, most likely less. If that confuses you I'm sure we can explain it better for you

Stymie · 07-21-2008, 09:05 PM

Quote:

Originally Posted by kghenson

Well actually, if you read my post

I am keeping it from shifting, so less strain. as to the motor I'm easy around 1700 to 2000 rpm which is well up on the torque curve.

So no extra heat, most likely less. If that confuses you I'm sure we can explain it better for you

im not confused... i've been around diesels long enough to understand what lugging a motor does to egt's. Tell you what, hook up a pyro, run up the hill locked in od, and then let it drop a gear. See what happens...