Just what does the Tow/Haul switch do on the 04.5 48RE. I have been told that it only turns off/on the OD. But recently I read someones thread that it also causes quicker lock up of the torque converter. I normally do not use tow haul unless tranny is hunting for a gear but have noticed that the trans slipage is quite bad when first starting out pulling my 11000# 5er. The reason for my question is that if tow/haul causes faster lockup then should I use it to start out and then turn it off when I get around 50 MPH to take advantage of the OverDrive on level ground. If it only controls OD off/on then I can not see any advantage to using it under normal conditions unless tranny is hunting gears. If my thoughts are wrong please advise as to what I am seeing wrong......

Thanks for any ideas or information

Don

 

To the best of my knowledge it not only locks out overdrive but also adjusts the shift points. I believe on yours it may hold TC lockup in 3rd and 4th but not in the others. The 06s have an O/D Off and a Tow/Haul. The Tow/Haul gives you TC lockup and adjusts shift points but still allows use of overdrive. O/D Off does the same except the addition of overdrive lockout. Probably isn't a bad idea to use it with that load unless your on flat ground to save your tranny. If I am wrong here I hope someone will correct me.

 

I'm a little confused as to what you're asking. You're converter is not going to lock up until 55mph under normal acceleration. So if you think you are getting slippage when first accelerating, the tow/haul button is not going to do anything at all.

 

I understand the slippage at first start but thought that I had read somewhere that by using the tow/haul I would get faster lockup and maybe alter shift pionts with Tow Haul on. I know it locks out OD on the 04.5 but wondered if it did anything else like altering lockup or shiftpoints as above therefore the question.

 

That part I guess I am not sure about. It was the 50mph thing I wasn't understanding. If it does shift points, I guess that would change under 50mph, but anything to do with the TC will not happen until highway speeds. You could always add a lockup switch, but you need a tripple disc before you would want to do that.
With my TC and VB, I don't ever use the tow haul button. My TT fully loaded is about 8500lbs and another 1500lbs in the truck and I don't need to use it.

 

You are missing out on the most important safety feature of the tow/haul function. The tow/haul brings on the bands for increased holding and engine braking on decelleration.

 

Is the breaking function for my 04.5 also? This is something new that I have never heard of...Thanks...

 

This is about the third time you have mentioned bands and TH. Just what bands are you referring to?


IIRC, TH on the pre-05's locks out OD and maybe a more aggressive TC lockup strategy. It may be able to influence the governor pressure some what to change shift points but not sure about that. It can't change TV pressure to provide more holding power and tailored shift points. It feels like an OD lockout and an aggressive TC lockup routine but not much more.