07 Classic Tow/haul Problem

racerx55 · May 5, 2007

I just got an 07 2500HD 4x4 WT, 6.0L automatic.

when i turn on tow / haul it does shift higher like normal, but my problem is on deceleration it will just free coast and drop to idle like an old TH350 with a stuck detent cable. just like if you put it in neutral.

the guys at the dealer are trying to tell me its normal yet they dont even wanna take the time to check it out. it cant be right.

say if i get it up to 2000 RPM in 2nd gear before it shifts into 3rd and just let off the gas then coast down a hill it will coast up to 50-60 MPH and the engine stays at idle speed. the trans never shifted into 3rd obviously because of t/h being on. but it has absolutely no holdback of any sort and i would have to rely 100% on my brakes just to keep a safe downhill speed. the only time it holds in a gear like normal and wont just drop to idle is if i manually shift into the same gear as the trans is staying in when im at a steady speed, or when it makes it to overdrive.

i hope this isnt normal but i want a second opionion before i go ream on someone at the dealer for not taking the time to look at my NEW truck with only 600 miles on it. i need to tow an 8,000Lb bobcat this weekend and dont really like the way this thing is working.

thanks for any replies. this is driving me crazy.

EDIT: to add another not i also notice a pretty big jump in trans temperature with t/h turned on, but i havent towed anything but an empty car trailer yet.

demented · May 5, 2007

I to say it, but the concern you have IS NORMAL. I don't like this feature either and don't know why they set it up this way . I tow heavy loads also and have found that the best way is to downshift the trans yourself.Most of the time I don't go any lower than third gear but on steep grades 2nd is used. I wish they had the same features as the allision tranny with the automatic downshift. Don't sweat it. I have found that the tow/haul mode is best used over 5000 lbs.under that I don't use it. And on the highway, even with a 10000 lb enclosed car trailer I don't use i the tow/haul mode. It wants to hunt for gears alot. Uses alot more gas.A light right foot and average speeds helps in this department.

racerx55 · May 5, 2007

what a cheap piece of s**t.

youd think by now theyd have a better way to control it then just holding the detent valve open a little bit.

you dont get very much engine braking when it holds in a gear but every little bit helps.

evrything you ever read about trailer towing tells you its dangerous to coast in neutral downhill and this is no different.

guess next time ill get an allison or a 5 speed. ive always hated automatics.

racerx55 · May 6, 2007

hey demented does you truck start out in 2nd gear if your manually shifted into 2nd?

i also notice if i manually shift to 1st it will upshift to 2nd anyway.

2nd gear start is nice sometimes for certain things.

demented · May 6, 2007

I never payed attention whether it starts off in second gear. I don't think it does,but, if it did I would have noticed it.I also have a super chip programmer on mine so I have adjusted the tranny to what I wanted.Much firmer shifts for towing.I have noticed that the programmer does make the tranny act differently,almost like it took care of some of the factory screw ups.Being around transmissions and race cars a good portion of my life I can say that the GM tranny sucks as far as a towing tranny but it does get a good review when you talk about strength and longevity(remember this tranny is based on the TH400 that has been around almost 50 years)Thats probably why they used it in these trucks.They are reliable.If the guys at GM took a little look at the programming for this tranny they might change the features to what people want in an HD truck.

racerx55 · May 6, 2007

yea they could do a little better with some effort.

mine will take off in 2nd gear unless you go WOT then it will downshift to 1st.i just pulled a ford exploder about 100 miles back from the ohio river through the long steep hills and this truck tugs it like it dont care and didnt burn up too much gas on the trip. i was really impressed with the engine and i did notice the trans temp has come down quite a bit since its got a fair amount of miles on it now. i took it really easy towing that bobcat yesterday, today i gave it all it had pullin that truck, i could accelerate to 80MPH uphill where my old 92 silverado with a 350 couldnt pull 2 quads on a trailer much over 50 gettin a running start.

what kind of programmer do you reccomend i realy dont need any more towing power from teh engine but i would like to adjust the trans some for daily driving, it shifts too early for the way i drive and its constantly back & forth through gears

normally i just pull my race car every saturday to the track but i do some occasional heavy towing.

redvett · May 7, 2007

The default is 2nd gear and will start in 2nd if selected & works great in sloppery weather.

demented · May 8, 2007

As far as the programmer goes, there are so many out there that chosing the one you think will be right for you might not live up to your expectations. I have the superchip flashpaq. After doing alot of research about them I chose the superchip because it was the safest with the most options. What I mean by safest is that they produced nice power improvements in a variety of conditions without worrying if it would harm the motor, tranny or computer. It also had some features like changing gear size, tire size, and transmission calibrations to correct the speedometer. It's probably not the most power oriented programmer but I own a Truck. It's meant to tow my racecar,not be my racecar.Don't get me wrong , I play with me truck, but playing is better with something thats designed to be played with. Just my 2 cents.

2017HD · May 8, 2007

Yeah, that is why I waited for the GMT900 and the new six speed that does downshift when going downhill. Just tap the brakes and it downshifts one gear - apply the brakes and it downshifts as much as needed and holds the lowest gear until the gas is tapped. I have not noticed any difference in tranny temp with either mode. As far as downshifting on up hills go, I have not noticed any difference between normal and T/H modes.

racerx55 · May 8, 2007

im not really a big fan of the engine braking of the allison, i just wish these would at least hold the gear theyre in instead of free coasting. ive had them dowshift on me around a corner and the trailer push me sideways when the rear wheels slid a little from the shift, then the trailer brakes jerk and makes it a little rough keepin it straight. that was in a pile of crap new ford so i assume the ally 6 speed is alot smoother about it since it doesnt have near the ratio jump to the next gear.

i just race in the 4 cylinder class so i get wound up on the street sometimes but i have another car for doin that. i suppose if i start messin with stuff on a programmer ill end up breakin stuff ( i'm well known to destroy things with my heavy right foot) and probly wont be covered under warranty.

what and where do you run demented?

dirt circle track is all i like.

demented · May 8, 2007

I know what you mean about the ford tranny's. They do suck. I race a pro modified mud drag car. It's a '23 altered tube frame car 4 wheel drive with a 622 ci bbc set up on alcohol and nitrous. It's a blast.Check it out. http://www.photoreflect.com/pr3/OrderPage....mp;po=64&c= I run in the NMRO circuit mostly from ohio to the east coast. Any racing to do with mud including hillclimbs and ice racing.

Nice rig · May 8, 2007

what a cheap piece of s**t.
youd think by now theyd have a better way to control it then just holding the detent valve open a little bit.

you dont get very much engine braking when it holds in a gear but every little bit helps.

evrything you ever read about trailer towing tells you its dangerous to coast in neutral downhill and this is no different.

guess next time ill get an allison or a 5 speed. ive always hated automatics.

Honestly...how hard is it to reach up and take it down a gear on the column???

racerx55 · May 8, 2007

well then if ya gotta shift constantly anyway then why do they even bother puttin the t/h button on?

your a little late for an insult but i wont take it personal.

clm7214 · May 8, 2007

yea they could do a little better with some effort.
mine will take off in 2nd gear unless you go WOT then it will downshift to 1st.i just pulled a ford exploder about 100 miles back from the ohio river through the long steep hills and this truck tugs it like it dont care and didnt burn up too much gas on the trip. i was really impressed with the engine and i did notice the trans temp has come down quite a bit since its got a fair amount of miles on it now. i took it really easy towing that bobcat yesterday, today i gave it all it had pullin that truck, i could accelerate to 80MPH uphill where my old 92 silverado with a 350 couldnt pull 2 quads on a trailer much over 50 gettin a running start.

what kind of programmer do you reccomend i realy dont need any more towing power from teh engine but i would like to adjust the trans some for daily driving, it shifts too early for the way i drive and its constantly back & forth through gears

normally i just pull my race car every saturday to the track but i do some occasional heavy towing.

I know what you mean about the tranny while towing. I didnt like the way the shift points were set up. I got a Predator and i changed all the shift points and firmness. I have it raised for normal driving and then i raised the shift points even more when the t/h button is on. I like the way mine tows now. It powers up the hills much better. Id rather spin more rpm than hunt gears.

prowler3 · August 4, 2007

im not really a big fan of the engine braking of the allison, i just wish these would at least hold the gear theyre in instead of free coasting. ive had them dowshift on me around a corner and the trailer push me sideways when the rear wheels slid a little from the shift, then the trailer brakes jerk and makes it a little rough keepin it straight. that was in a pile of crap new ford so i assume the ally 6 speed is alot smoother about it since it doesnt have near the ratio jump to the next gear.
i just race in the 4 cylinder class so i get wound up on the street sometimes but i have another car for doin that. i suppose if i start messin with stuff on a programmer ill end up breakin stuff ( i'm well known to destroy things with my heavy right foot) and probly wont be covered under warranty.

what and where do you run demented?

dirt circle track is all i like.

I have to disagree (but...to each his own ). I love the way my '06 GMC 2500 HD's Allison works on downhill grades in Tow/Haul mode! I just got back from 2 weeks in Glacier and Yellowstone with my Fleetwood Bayside hitched up and was very impressed. I hardly ever used the brakes on grades...and a slight tap on the brakes would downshift the Ally...SWEET! It may be less smooth with a diesel (??) but I have the 8100 Vortec...I REALLY love my truck!