We're new to towing a fifth wheel. We're towing a 11,000 lb (loaded) unit with a 2005 CTD 2500 LWB with auto trans. Would like to know if it is best for the engine and trans. to leave the truck in cruise for as much of the time as possible (including hills) or use the throttle for going up hills. Have been told both ways by different people.

 

I see nothing wrong with using the cruise when towing. I've been doing it with my 99 since I got it. My Dad also used the CC on his 05 when they pulled their 10k 5er from VA to CA, up to WA, then to WI and back home. Dad was very impressed with the performance of his new CTD/automatic.
Some folks (myself included when my truck was stock) will use the accelerator pedal to increase the speed a little above the CC setting when starting up a grade, so as not to lose too much speed before the CC can react. However, I think the newer and/or more powerful trucks do well without doing this. I rarely do this anymore since adding the mods in my signature below. Just my $.02

 

I use the cruise on flat and mild hills when towing. If its a long/steep grade I shut the cruise off and use my foot. The way I see it is that with the cruise on it just keeps pushing down on the Go pedal to try and maintain speed. It doesn't take into consideration engine temp and lugging the engine. I feel you have more control over the rig without the cruise on when pulling a hill.

 

I'm with Buckshot - - I use the CC only on flat land. I allow the rig to creep up a bit in speed going down a hill rather than pull off the throttle all the way. Then, I have a little extra speed starting up the hill on the other side and I don't push it hard to maintain a certain speed - - Allow it to do it's thing. I have done short tests, like 10 miles at a time, with the computer in hills. I can get about 1 mpg better mileage with my foot than with the CC.
Bob

 

That may be true with a manual transmission, but what about us folks with automatics? I can only speak of the way that my truck performs with the modifications that I have done mainly for towing with the 47RE tranny and fueling enhancements. Actually, I was surprised on my first haul up Afton Mnt on I-64 in VA, with the current set-up. I had the cruise set at 68 in OD. I decided to leave it alone and see where it would downshift now that I had the DD2 injectors. To my surprise, it dropped to about 64mph and stayed there in OD, right around 1900 rpm and 1150-1200*egt. Now this grade is not super long, but when the truck was stock, it would downshift about a quarter of the way up at which time I would lock out OD. There were also several other places along this routinely traveled route where it downshifted when stock and now does not. Once again, this is my modified truck, with gauges and apparently a real good set-up for me.
"Pulling off the throttle all the way" with a 47RE unlocks the TC and basically feels like throwing it in neutral!
I'm not sure on the new 48RE, which is what ehefley has in his 05, but my 47RE does gain 4-5mph downhill (depending on the grade) while in CC. However, I have found that the CC will actually keep the TC locked and provides some fairly good engine braking. My Dad was saying that his 05 48RE performed great in this department and actually downshifts on its own to maintain the desired speed on downhill runs. Remember, there is no way to lockout OD on the 48RE like I can on the 47RE. I know that the automatic folks are still not convinced about the changes to the 48RE and most would still like to have the option of locking out OD. This may be coming in the 06 I think I've read somewhere. As I said, Dad was very impressed with his and basically used his CC like I do.
I also responded to ehefley's post based on his use of the word hills and not mountains,,,,,, course "one man's hill is another man's mountain!"
I do tend to agree with Bob concerning the fuel mileage,,,, I would imagine it does take a little more fuel using CC. I've never checked.

 

I tow using cruise all the time. I don't allow it to shift down while in cruise.I shut it off when I get into hills. I can feel the kickdown in the go pedal and if It is still losing speed. I'll start driving the tranny like a manual. I don't allow it to shiftdown automatically in hills loaded, to much stress and the shock load on the tranny is where the heat comes from. My first move is to get it out of OD I even let up on the throttle let it shift then back on it. If it still pulls me down I'll go to 2nd...let up then shift then back on the throttle and try to keep it smooth. Same when shifting up....I have had 2 47re in different trucks and never a problem.

 

I pull with mine in OD on flat roads and small hills. I think I have the power to pull in OD but I start to get a shudder when I leave it in OD so I just take the OD off. The hills around here are usually long and steep and they bleed off the speed easily in OD.

 

I might add when in 2nd you can't go over 45mph . someone correct me if i'm wrong

 

I dont have cruise...so its foot only.

 

I just got back from a 350+ mile trip towing my Jeep on my 16' flatbed. Lots of long rolling hills on the way to and from PA. Once on the interstate I kept her in 6th and used the cruise most of the time (except construction zones). The Cummins pulls like a champ, never dropping speed. EGTs got to almost 1200 once on a loooong hill.

Of course my trailer only weighs in at about 6000lbs loaded...

 

Tow yours in o.d, if it can stay in 4th gear without shifting back from 4th to 3rd CONSTANTLY. I've towed with 3rd gen all stock about 18,000lbs GVCW and it pulled great in o.d. and rarely kicked out. Throw on a mild towing chip and you'll laugh at how easy it is to cruise up hills in 4th.

With my setup even on larger hills, with cruise on and no extra throttle before hitting hill, I can almost always stay in 4th gear o.d, and maintain same speed. If hill is excessively long, it will eventually kick into 3rd, but it will maintain original speed also. My GVCW is 19,000 lbs, it's an awesome pulling combo.

 

Note that several posters have earlier models -
they are able to lock out OD.

The auto trans on the '05 goes into OD even
in tow/haul - no lockout.
[tow-haul just changes shift points]
Changed back in '06.
JC

 

I've done the same thing and also got 1mpg+ better than the CC. My CC is a bit of a lead foot when it finally does kick in!!!!

 

Ditto - I go from 14 to 13MPG when I let the CC manage my speed through the hills.. but I'm lazy like that most of the time..