I boughyt a TT 14 months ago, 32 foot, weighs 8500-9000lb loaded. I had a 95 F150 that I had to get rid off because it would not pull it. I was getting 5mpg and worked it way to hatrd to maintain 45 mph, never saw 55. I bought a CTD, and was pumped. I am know starting to wonder if I made a good descision or not.

The TT is not an enclosed under belly if that makes a difference and the only difference in my truck not in my sig is exhaust and intake. I get my best mileage at 60 mph and do not mind towing there (firends very small gasser I go with has to) so end up starting there. It runs at like 1600-1700 rpm. The only problem is here in Iowa any rolling hill willl send it dwon shifting and running around 2500 rpm. It does not then want to leave 3rd, I ahve to speed up and let off to get it to shift. It is like it is on the bubble right there. I have increased speed to stop it and at 70 it will hold the speed and not down shift (1900-2000 rpm) on these rolling hills, but my mileage drops from 13-14 to 10-11.

I have now 13000 miles, itn just seems that it should not be on the bubble at those speeds and then dropping so fast in mileage above them.

Now my trailer may just be a big pig, it is a square box. I was told that enclosing the underbelly would help. Yes, I would have a fifth wheel right now except the trailer was bought first, and the old truck had 8 inches of lift so bought a TT.

Is this just the way it is, I was expecting 15 mpg running 65-70 with this trailer that ways peanuts of what the truck is capable of.

 

I would just let the trans do what it has to do. If you don't want to speed up, don't. The transmission should eventually shift out of it. Are you using haul/tow or not?

I am not positive, but mileage wise, you may be better running 2500 RPM at 60 in 3rd than 200 RPM at 70 MPH in OD.

You are in an interesting spot because 1600 is lugging a bit... so it probably doesn't want to shift back down.

In termsof what you were expecting... how many miles on the motor? There are a lot of factors... 4x4 and auto will both hurt mileage, and a new truck needs to get broken in first.

 

What gear ratio is you rear end? Also, have you weighed your rig? The biggest mistake is folks read the label and think that's how much it weighs. WRONG! The label will never include how much stuff you pack/cram into it. And most of the time, the label is the UVW. Unloaded Vehicle Weight. That's the the mfg says it weighs BEFORE they add all option. Options are the fridge, ac, heater, microwave. w/h, slide, fancy cabinets, and so on.

 

You need to use the tow / haul button or you are going to burn the tranny up. Read the owner's manual and understand how to use it. It is there for towing!

 

It sounds like you 3.73 gears.
You'll have to run faster so your rpm's stay up, or slow down, and drive with OD off.

 

According to Cummins website and PowerSpec, you should be running 2150-2250 at 65 and no lower than 1900.

http://www.powerspec.cummins.com/site/home/

 

great info thanks guys I knew on the way home yesterday that my confusion would clear when I could get to a computer. The truck has 13000 miles now and yes 3.73 gears.

I am knew to diesel and dodge, but I always tow in tow mode so not to worry there. I ahve not been takeing it out of OD unless the tranny heats up from shifting alot which has never even come close to happening yet.

I have been watching my tranny temp gauge closely when I let the tranny do its thing, and no problems never goes over 160 degrees. The mileage seems to realy drop when it runs in third gear at 60 mph is why I wondered.

I wondered if 60 was just to slow and 1600 rpm was lugging it. I thought aboutr telling my buddy see ya, sorry, and speeding up. So you all think that 2150-2250 (what cummins said) is the sweet spot which would be best mileage and power right?

 

sorry I forgot the trailer says 7300 dry weight. I figure 8500-9000 once we pull out the drive.

Also what kind of mileage can I expect at 2200 rpm

 

Anyone on mileage at 2200 RPM

 

Hmmm, maybe your expectations are too high? Or maybe your foot is too heavy? I dunno.

With my truck (albeit a slightly different than yours - a little older, 4.10's and 6 speed) I'm averaging 17.4 mpg over 54,000 miles of all kinds of driving and that number is unloaded. So to pull 9000 lbs of shoebox at a 2 mpg penalty might be too optimistic.

Pulling my boat ~9000 lbs back there fully gassed and full coolers, I get around 13.5 mpg. And remember, my boat is streamlined compared to your trailer. My old F350 (460 gasser) got 5-6 mpg pulling the boat, and 9 mpg not pulling the boat - in any event I'm a happy camper.

BTW, my truck likes 2100-2200 rpm on the highway.

 

I get 13-13.5 pulling my 9500lb 35ft TT. I have a 4x4 with 3.73 gears. Haven't had it in the mountians yet, but pulls nice on the small hills at 65mph in tow/haul . . . doesn't seem to hunt for gears. My 6.0L Powerstroke got 9mpg pulling the same trailer . . . I'm thrilled with 13mpg. To be fair, I had 4.30 gears in the Ford.

 

Firstdodge, does your trailer have the enclosed underbelly?

Maybe I have been lugging it to much towing at 60-65 with 1600 rpm. I would not complain about 13mpg consistent. I should probably just get it to 2000 or so RPM and leave it and stop sweating the mileage for a while.

 

No . . my underbelly is hanging out . . . in both instances

 

While towing my 38 ft fiver 10,200 # @ 65mph I get 13 on flat ground. through hills it will drop to under 10 but the speed stays the same.
I'm very pleased with my truck performance.

 

When I moved after the Marine Corps from SoCal to WA State, I towed a 26 foot enclosed car hauler (total weight truck and trailer 18,100#), I averaged 12 mpg doing 70-75 the whole way. The slowest I went was up the MT/ID Lookout Pass was 48 mph. I didn't even go that slow up El Cajon pass.
That was just with my 4" exhaust, BHAF, EZ. Overall, I enjoyed how my truck pulled until I put the comp on.