07 48re in tow/haul will go into 4th converter locked as low as 48mph and higher depending on throttle. If you're on the throttle up a hill it won't shift into 4th till much later and will sometimes stay in 3rd until you've backed off the throttle sufficiently.

 

Yeah, I know, I have an 06 which is the same. OD engages around 50mph right after 4th. (Depending on acceleration you can feel 4th or not). It OD also drops out immediately under 50 which can be annoying, caused by slow dinky traffic


I'm asking about the 05 or any of the 3rd gens 03-05 because I don't own one.

 

I've noticed 3-4-OD likes to hang if I'm slowly creeping up on 50. But it will drop in quickly if I'm on it. A little irritating for roadways that are 45mph

 

TH on the '05 does use OD. It only adjusts the shift points slightly and uses lockup in the Torque Converter in 2-4 gears.

 

My 2005 is in OD by 48-50mph. It seems to me it will go 1-2-3 and stay there at a 30mph road around here. Get up to the 40 range and it will go into the 4 and by 48-50 the OD kicks in., Tranny really grabs at 48-50.

In TH it seems like the truck runs about 300rpms higher then it would in regular mode. I cant say I have run it up to highway speed in TH so I am unsure if it kicks into OD at 50mph or not. I guess I will find out this weekend! Sadly I havent pulled a trailer yet with my Cummins. I do know running around town in TH is more fun. Seems like the truck responds quicker.

I've also put it in TH to get it to warm up a tad faster as it runs higher rpms.......that first start and drive of the day in the cold we have had it seems to get things warming a little quicker. I would also think in slow grinding traffic TH would be better on the truck.

I do know the Cummins has been hard to get used to compared to my 95 Ram 360. It will shift and be in OD at 30mph while the Cummins will not shift all the way to OD at 30.

47

 

I'm not sure why you wouldn't use it. It is designed to make the tranny more effective when towing. There is no negative effect to using it on your '07 so I would. I notice zero difference in fuel economy when using it verse not using it.

 

I think you're feeling the torque converter lock-up somewhere in there. Your 48RE is only a 4 speed.

T/H reprograms shift points to keep your RPM up to help protect the transmission.

 

Yes I called lock up OD. Theres 5 points you can feel getting up to speed. The gasser went right up into OD by 30mph and the diesels will stay down usually 2 shift points at 30mph.

47

 

I run my '07 in tow/haul ALL the time.
The stock TC is so loose that I prefer the way the truck performs when it's locked.
I've got 99K miles and it's my tow vehicle...stock tranny w/regular maintenance. Tranny works great (knock on wood)

I'll probably need a rebuild at some point, but I'll be real happy if I can make it to 125K miles