Ok so i have a new 2007.5 2500 with the 6.7 and the auto six speed tranny. today will pulling my 35ft trailer in tow haul mode when starting to slow down the tranny would down shift and it would hit so hard it would jerk the whole truck and trailer, now it did this week the exhaust brake on and off, but if i really jumped on the brakes it wasnt as bad, is this normal or should i take it to the dealer, truck only has 2500 miles and this was the first pull with the truck. computer said i got 15.2 and when i manual figured it out i got 15 pretty good to me.

 

I noticed on the way home from the dealership. (1000 miles). LOL but seriously, it did jerk while in tow mode downshifting. I also noticed like around on the higher gears right before it shifts, it slips sometimes only if your kinda getting on it. I havent towed yet but I will in a few more days. For now, im letting it be cause its new. Im thinking that the computer would recognize my driving and shift better and everything is just breaking in. but we will see. So far I luve my new truk. No codes as of yet. Bout to purchase a quadzilla tow module once it comes out for 6.7.

 

Yeah, mine "hits hard" too when using tow/haul & the exh. brake which is why I "don't" really use them. I can't believe that all that "hitting hard" while downshifting isn't putting ALOT of stress on the drivetain or can be very good for the truck on the whole. When I'm towing and see that I might need the exh. brake I then switch it on. Have to "drive" or keep a watch way ahead of the truck to do that. When I'm towing heavy I use the tow/haul ONLY for starting out from a dead stop, go thru the first 3 gears and then turn the tow/haul off.

 

ok if i read the owners manual right , the only thing the tow haul mode on these trucks do is lock out 5 and 6 gear untill it senses a good cruising speed and then the tranny will let it shift to 5, so if we use the manual shift lever and do this manual we then in sense wouldnt get that hard down shift. and along with the jake brake it should be ok?????????

 

FWIW, my buddies truck does the same thing. He says it's downright dangerous to drive with the tow/haul and the EB on when the roads are wet.

 

Mine was doing it at first but when going to and from a 4000 mile trip with my 11K 5th wheel in tow it worked great slowing my truck and trailer. Mine does not jerk like it use to and is much smoother now. The dealer said that the trans will learn how you drive like the Allison does so maybe that has something to do with it.

 

I know one thing, every Super duty the in-law has owned has about thrown me into the steering wheel when it downshifted. I hated the torqshift. I thought it was one of the worst trannies ive ever driven with. When i drive the new 6speed it feels smooth as glass compared to the torqshift. I drove with it in tow-haul to feel it out and cant said it downshifted hard at all. But i wasnt pulling anything.

also the torqshifts were behind 6.0s. I will note that my friends 6.4 feels to shift much smoother.

 

I liked the torqshift, I think it's a great tranny. But, it does shift hard in tow haul mode when it downshifts. It didn't "throw me into the steering wheel" but they were hard. And yes, the torqshifts in the later 6.0's and the 6.4s are much smoother than eariler ones. but that tranny can hold quite a bit of power before it has to be built up.

I drove a 6.7 and the 6 speed shifted very very nice. I think it's awesome. But I didn't try the tow mode.

 

His 2005 6.0 started to slip when pulling a 7k lb empty flatbed gooseneck. This was one of the truck that shifted so hard. I guess he just had bad luck with the trucks he got. That truck had quite a few more issues as well. I guess his trucks ruined it for me. But i will say that his 07 6.0 shifts a little bit softer but not near as nice as my friends 08.

People will always get a bad truck here and there no matter what brand it is and i realize that but his truck just kinda ruined it for me i guess.

 

I had the torqshift also before buying a new 6.7 and I agree that it downshifted very hard but I never once thought it was hurting the transmission....

 

When you're in tow/haul it's also locking up the torque converter sooner and will keep it locked longer and at lower speeds. If you are pulling fairly heavy loads this reduces TC slippage and keeps the transmission cooler.

If you use the EB out of tow/haul, the trans will not automatically downshift like it does with T/H turned on, so it will be much smoother but provide a lot less stopping power. As you slow down, with T/H off, the torque converter will disengage sooner so the EB no longer provides any stopping power.

I tow very large and heavy boats through the 12K foot + mountain passes in Colorado. I have found the EB in T/H works great coming down those long steep grades since that alone will maintain my speed and I never have to use the foot brake.

BUT, if you let off of the gas and it starts to slow down, as long as you keep your foot off of the gas the truck thinks you want to keep slowing down and it will keep down shifting and applying the EB hard all by itself until you get down to about 25 mph when the torque converter kicks out. I have found that if I let off the gas to get the EB to kick in and slow my acceleration, then feather the gas pedal just enough to cycle the EB off, I can maintain my speed without the trans down shifting hard or at all.

If you aren't used to the EB (I had a 6.0 and TS before too) and 6 spd it does feel harsh, but it just works that way. Put some more miles on it and try some of these other things to see if that makes it better.

 

thanks that explains alot and i can see i just need to learn the truck, totally different then my 6.0 thanks again buddy

 

Nice job explaining the operation of TB & TH combo.

 

i had some seriously rough shifts...not only in T/H mode...took it to the dealer, got an tranny controller update and it shifts alot better now.

 

do you have the update or tsb number for that so i can ask my dealer?

thanks