Tow Haul newbie help please

[bigbob7777]

I have a new 05 DRW 3. 73 auto and towed a new 13k 5th wheel this weekend from Missouri to TX. Been reading some posts about tow/haul and it says when in t/h mode, some engine breaking will occur on downhills.



When travelling through the mtns in MO and AR, it didn't notice any downshifting as some have mentioned and had to "tap" break several times to slow down. This is with t/h on.



Can ya'll clear this up for me? What is the correct procedure to use t/h in hilly/mountainous areas?



Also, how do you downshift from "drive" to 3rd gear. I only see a downshift option for 2nd and 1st gear? Is it best to use 2nd gear manually on big hills to keep the rpm's up - but won't the auto drive do this for me (and cruise control)?



Sorry if these are elementary questions, just never had this combo before.



bob

 

[mberry]

Most likely they are referring to the torque converter NOT unlocking when you take your foot off the gas pedal. It's probably not what you were wanting to hear.

 

[desertryder]

to downshift from drive to third gear the only way is to push the tow haul button and take it out of overdrive and into 3rd.

I just came home from a 3500 mile trip through Idaho with many hill climbs. and indeed my transmission did downshift automaticly when I had it in overdrive coming down a hill.

as my speed built up with no accelerator pedal the computer must have sensed this and bingo my transmission downshifted by itself into the next lower gear to attempt to slow me a bit. .

when I started to add fuel it would up shift on it's own.

as I got to put a load on the engine I always left the transmission in tow/haul position.

I did manually drop her into 2nd on a few down hills because I was towing 2 trailers and didnt want to smoke my brakes.

Not sure what this does to the torque converter but hopefully someone else will let us know. It worked for me and got 12. 5 miles per gallon average over the entire 3500 miles towing a fifth wheel and an enclosed motorcycle trailer behind that.



hope this helps

 

[RMalone]

The 05 48re doesn't lock out 4th/overdrive, the 04. 5 does. As I understand it the 05 will maintain lock-up and downshift when in tow-haul mode,

but when satisfied it will shift into od while in t/h mode.



Down shifting and staying locked up will only slow a load sooo-much, diesels don't really offer much "engine breaking" so the only way to avoid the discs is with an exhaust brake.

 

[bigbob7777]

anyone else have any suggestions, please.



bob

 

[BHolm]

This is starting with the t/h engaged. To get the trans to drop into 3rd from o/d, momentarily take it out of t/h and then back in. It will drop a gear and lock the convertor. It will stay like this until you touch the gas again.



I think that there is enough engine braking for the trucks rated capacity without using an exhaust brake. I recently ran all the passes on I-70 in CO at 22k GCW and had no problems. You are forced to carry less speed down something like the back side of Eisenhower tunnel than you might if you had a jake but 50-60 mph down that is plenty for me.



The t/h works much better going uphill IMO. It locks the convertor much sooner and pulls the grade pretty efficiently. Coming down, it is nothing like the Allison, but works if manipulated a little within its capabilities.



I have not found the auto lock-up or downshifts to be as consistent as I first thought. Cycling the t/h button does get the downshift though so at least you can roll against third gear instead of fourth when you chose. Obviously you can shift to get second gear. Hope this helps