Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!

1 - 20 of 46 Posts

·
Registered
Joined
·
70 Posts
Discussion Starter · #1 ·
Today was my first day trying my 2007 LMM out pulling my horse trailer. The trailer is a 16ft gooseneck that weighs about 3500lbs emtpy. Fully loaded, it will weigh around 6000lbs. I'm getting knew tires on the trailer tomorrow and a brake box installed on the truck, so I don't if it has anything to do with the hauling today.

Anyways, I tried out the tow/haul mode on the truck and was a little curious. The truck got alot louder and didn't drop under 2000rpms. This is mainly in stop and go traffic in town moving no faster than 40mph too. No hills either. When I took the truck out of tow/haul mode and just hauled the trailer in "drive", the rpms dropped and the engine went quiet again.

Now, I used to haul this same trailer with a chevy 1500 extended cab truck. Never came across anything alarming when hauling like this, but I also never encountered hills or was on the road for more than a couple hours per trip. I may be hauling a horse home from WV this weekend, so I want to get all this right before I go. Does this sound right to you? Nobody I know has a newer duramax to compare to aside from Fords and Dodges.
 

·
Registered
Joined
·
166 Posts
Mine didnt do anything like that.
 

·
Registered
Joined
·
75 Posts
when tow haul is engauged it will hold gears longer so your rpm wont drop to low on the shifts. works very well with heavy trailers. also u will not get 6th gear on the highway very often in tow haul. If your pulling only 6000lbs its up to you if you want tow haul on or off. I usually turn mine on in town or stop and go traffic but then turn it off on highway to use 6th gear. Just watch your egt gauge if your in 6th pullin heavy tends to get warm fast lol! also if you dont use tow haul very often or your trailer weight varys alot it will take the transmission a several miles to learn how to shift like it should. The allison has a learning computer so it will shift better the more miles you are loaded down.
 

·
Registered
Joined
·
607 Posts
Today was my first day trying my 2007 LMM out pulling my horse trailer. The trailer is a 16ft gooseneck that weighs about 3500lbs emtpy. Fully loaded, it will weigh around 6000lbs. I'm getting knew tires on the trailer tomorrow and a brake box installed on the truck, so I don't if it has anything to do with the hauling today.

Anyways, I tried out the tow/haul mode on the truck and was a little curious. The truck got alot louder and didn't drop under 2000rpms. This is mainly in stop and go traffic in town moving no faster than 40mph too. No hills either. When I took the truck out of tow/haul mode and just hauled the trailer in "drive", the rpms dropped and the engine went quiet again.

Now, I used to haul this same trailer with a chevy 1500 extended cab truck. Never came across anything alarming when hauling like this, but I also never encountered hills or was on the road for more than a couple hours per trip. I may be hauling a horse home from WV this weekend, so I want to get all this right before I go. Does this sound right to you? Nobody I know has a newer duramax to compare to aside from Fords and Dodges.
Sounds normal to me. How long did you leave it it tow haul for? It was probably loader because your fan clutch was engaging due to the stop and go traffic and the higher rpms. Usually tow haul runs the rpms up higher before it up shifts and when you are decelerating, it keeps the rpms up where it has more back pressure to help slow you down. I bet if you would of sped up a little more over 40 it would of finally shifted and dropped the rpms. Plus, if that is the first time you used tow haul it might needs time to learn the shift points.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #5 ·
I'll get it out on the highway tomorrow to see how it does. I needed to haul the trailer to the tire place so they could size my trailer and check some things for me, so I'll give an update.

I only had the truck in tow/haul mode for about 15 minutes. It is the first time I pulled with the trailer. I just bought it at the end of December and then took it for a contract up to WY. I had zero problems with it in the cold weather and got my hitch installed. Now I'm getting my trailer right with the truck so I can haul my horse to NM next week even if I don't go the WV this weekend to buy another.

Dustin, what's the EGT gauge? I don't have anything aftermarket on my the dash cluster. The truck does have an MBRP exhaust, but the DPF is intact although I haven't been able to tell if it ever does a regen cycle. I was watching the transmission temp via the dash it got to 170degrees at one point. It usually runs between 120 - 150. I figured the temp change was because of hauling in town and stopping at EVERY red light. Also, just so I understand, 6th gear is the transmission when in a sustained speed of like 60mph, right? Best for fuel mileage? I just came home from WY a couple days ago and averaged 20mpg at a speed 70mph. When I got to my sustained speed and put the truck in cruise, the rpms seemed to settle at 1500ish.

Since I'm thinking about it, the literature in the book has me a little confused. I'm still thinking that I have to install my own brake controller to work the trailer's breaks. The tow/haul bar on the steering column has plus/minus controls on it. Am I thinking right that the truck's computer can intergrate the box so that I can use those controls to change the break strenght on the trailer? Or am I completely off? I can already plug the trailer pigtail into the the truck and get all my lights on the trailer to work. Also the "parking assist off" message comes up on the DIC everytime I hook to the trailer. Is this normal?

I know it sounds dumb to ask, but I've never had a truck with so many perks before.
 

·
Registered
Joined
·
75 Posts
An egt gauge is exhaust gas temperture. its how hot the gasses are that are spinning your turbo. If u do not have a tuner on the truck it is not as important. But i would make that your next mod its a very good gauge to have so you do not melt anything. i would also get rid of the DPF right away and block your egr with a blocker plate. you will get way better mpgs and your truck will last longer. If i remember correctly the lmm trucks have a brake controller built in so you should not have to buy another brake controller. You should just be able to plug your trailer in and the lights and brakes should work. the plus and minus should adjust your brake gain or braking power of the trailer. And 6th gear is overdrive and usually around 60 to 65 it will shift into 6th and 1500 rpms sounds good at around 65 and yes 6th helps with mpgs. The tranny temp of 170 is perfectly normal. i have seen temps of almost 200 when pulling heavy in the summer. the park assist probably does turn off with trailer attached because the backup sensors see the trailer and would beep all the time. just guessing on the park assist tho i dont have that in my 06 lol .
 

·
Registered
Joined
·
607 Posts
The plus and minus on the shift lever is to upshift or down shift manually. If you have a factory brake controller it will be located by your left knee.
 

·
Premium Member
Joined
·
410 Posts
I've got the same year truck. LMM. I have a factory brake controller, as mentioned, by my left knee. when the trailer is connected proper the DIC tells me 'trailer connected'

I don't have the parking assist.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #9 ·
Factory break controller means installed after market right? There was no break box on the truck by my left knee. I can plug the trailer pigtail in and get all my body lights, turn signals and break lights to work but I can't tell if the actual breaks are working. I used to have to manually set them with the controller on the old truck and could still never match them perfectly.
 

·
Registered
Joined
·
7,904 Posts
I'll get it out on the highway tomorrow to see how it does. I needed to haul the trailer to the tire place so they could size my trailer and check some things for me, so I'll give an update.

I only had the truck in tow/haul mode for about 15 minutes. It is the first time I pulled with the trailer. I just bought it at the end of December and then took it for a contract up to WY. I had zero problems with it in the cold weather and got my hitch installed. Now I'm getting my trailer right with the truck so I can haul my horse to NM next week even if I don't go the WV this weekend to buy another.

Dustin, what's the EGT gauge? I don't have anything aftermarket on my the dash cluster. The truck does have an MBRP exhaust, but the DPF is intact although I haven't been able to tell if it ever does a regen cycle. I was watching the transmission temp via the dash it got to 170degrees at one point. It usually runs between 120 - 150. I figured the temp change was because of hauling in town and stopping at EVERY red light. Also, just so I understand, 6th gear is the transmission when in a sustained speed of like 60mph, right? Best for fuel mileage? I just came home from WY a couple days ago and averaged 20mpg at a speed 70mph. When I got to my sustained speed and put the truck in cruise, the rpms seemed to settle at 1500ish.

Since I'm thinking about it, the literature in the book has me a little confused. I'm still thinking that I have to install my own brake controller to work the trailer's breaks. The tow/haul bar on the steering column has plus/minus controls on it. Am I thinking right that the truck's computer can intergrate the box so that I can use those controls to change the break strenght on the trailer? Or am I completely off? I can already plug the trailer pigtail into the the truck and get all my lights on the trailer to work. Also the "parking assist off" message comes up on the DIC everytime I hook to the trailer. Is this normal?

I know it sounds dumb to ask, but I've never had a truck with so many perks before.
If your talking about the plus minus buttons on the shift lever those are for shifting gears manually. Its been awhile since ive been inside a 07.5 +
but I think the trailer brake controller is by your left knee.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #11 ·
DIC doesn't tell me if a trailer connected. Is there something special u do or do you just plug in and go?
 

·
Registered
Joined
·
607 Posts
You don't have a brake controller period and you need to install an aftermarket one.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #13 ·
That's what I'm figuring on.
 

·
Registered
Joined
·
947 Posts
You can shift into 5th gear and leave it there if you want. Most guys report better mpg while towing in 5th. I do it with mine if I think the trailer is a little heavy, light loads I just let it use 6th. Using the tow button is kinda like an electronic shift kit. It will hold gear longer and shift firmer, and then you can go back to normal for daily driving. I use tow mode in traffic a lot since it also engine brakes for you too.

I highly recommend an Edge CTS for watching the vitals. You can set alarms to go off when things are getting hot. It's pretty easy to add their EGT temp probe in the exhaust manifold and the CTS just plugs into the OBD port. I use the Race version to program my truck and it ignores the EGR code since my EGR has a blocker plate installed. You can save $ if you just get the CTS Insight, if you don't want to use it for programming, its just a monitor.
 

·
Registered
Joined
·
607 Posts
You need to hardwire the brake controller's harness (from the aftermarket brake controller you purchase) to the harness under the dash, hook up 2 red wires to the power distribution box that are bundled up and possibly add a fuse or 2. One red wire is bundled up to a wire loom in between the power distribution box under the hood and the fender and the the other one is just above the drivers frame rail down by the steering shaft. When you take off the cover to the power distribution box, you will see to studs on the front side of the box, this is where you will hook the red wires to.
 

·
Premium Member
Joined
·
410 Posts

·
Registered
Joined
·
947 Posts
Look into a Prodigy brake controller if you determine your truck didn't come with the factory installed unit. They are super simple to plug into the truck and then just mount it under the dash by your leg. I've had my Prodigy on my last 3 trucks, prob had it around 10 years?

I bet the tire shop guys you're using could help explain this stuff also, if they have been working on cars very long. Or find a trailer store and go talk to them.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #18 ·
O yeah. I'm going to get my money's worth out of them tomorrow.
 

·
Registered
Joined
·
607 Posts
Any good hitch shop will know exacty what you need and be able to get you setup.
 

·
Registered
Joined
·
70 Posts
Discussion Starter · #20 ·
I think the closest I have to a hitch shop is U-Haul. I know a couple machine shops will install the hitches. Not sure if the mess with break boxes.
 
1 - 20 of 46 Posts
Top