Downshifting AT

[BHowell]

I'm planning to be traveling to the Smokey Min. area next month with my 5th whl. and need to sharpen up my driving skills especially when running downhill. How do I downshift the AT into 3rd gear. I seem to remember driving in the tow/haul mode and switched out of the T/H mode and noticed that the transmission downshifted. Is this the accepted method of selecting 3rd gear?

Sorta wish I had the late model auto trans. with exhaust brake and all. :{

Thanks,

 

[Hoefler]

While in tow/haul, turn it off and turn it back on, it will shift into 3rd and stay there until you press the accelerator.

 

[BHowell]

Thanks for the tip! I'll give it try.

 

[jelag]

Bill, you don't mention if you have an exhaust brake... . without the software and firmware changes to your 05 automatic going down hill is free wheeling... ...

Once your foot leaves the throttle on the automatic the ECM on the engine and the transmission release the pressure in the torque converter and there is coupling between the engine and transmission for de-acceleration... . your just free wheeling almost as if you'd put the transmission in N...

 

[BHowell]

jelag,

Nope! No exhaust brake. Are you saying that my only option is to ride the brakes on a downhill?

 

[RVTRKN]

The golden rule for the big rigs on a downhill side of the grade is, "what ever the lowest gear is you use to get up the grade, you should use one gear lower to go down the grade". Don't down shift on the grade, down shift before the grade and obey the semi truck speed limit. You should brake your speed to 5 MPH less than the speed limit and then as you gain speed back to the speed limit brake back to the 5 MPH lower than the speed limit, do this until your off the grade. I know its harder to do this with an automatic, but if you follow this advise, it will give you a better understanding of your rig and be able to learn the capabilities of your rig, you will have started on the safer side of error.



I believe your trans is not compatible with the exhaust brake due to a weak thrust washer in the trans, this could be incorrect, but I know you should make sure of this before you install one. Not to steal the thread, but this is the main reason why I like the standard trans. When going downhill with a standard trany you have full control of using the engine to brake your decent. Its even a bigger plus to have the exhaust brake helping you to brake. There will be a lot of arguments on this subject but that is why 99% of the big rigs have a standard trany'



Good luck on your trip and stay safe.

 

[bmoeller]

The golden rule for the big rigs on a downhill side of the grade is, "what ever the lowest gear is you use to get up the grade, you should use one gear lower to go down the grade".

I don't think that "golden rule" really applies anymore. At least if you run a truck with a powerhouse under the hood. I can pull LOTS of big hills in O/D, or at least the top 4 gears (of 13). And, depending on the load and grade, dropping a single gear might not be enough. Albeit, it should be in a pickup truck, most of the time.

Don't down shift on the grade, down shift before the grade and obey the semi truck speed limit. You should brake your speed to 5 MPH less than the speed limit and then as you gain speed back to the speed limit brake back to the 5 MPH lower than the speed limit, do this until your off the grade. I know its harder to do this with an automatic, but if you follow this advise, it will give you a better understanding of your rig and be able to learn the capabilities of your rig, you will have started on the safer side of error.

I have found that going as much as 10mph under the posted limit going down long grades, and using LIGHT, steady pressure on the brakes to be better than letting up, and pressing down. The faster you get going between brake applications, the harder you tend to need to push on the brake pedal to slow down. And, in doing do can heat up the brakes even quicker, leading to brake fade and smoking brakes.

I've been on plenty of 10-13% grades out east with a big truck, and doing the above has served me well. So has a Jake with a 600hp brake rating.

Also have some places near me with 6% grades, and the towns have a brake ordinance. So, I usually slow down as much as 20mph under the posted limit, and go easy on the brakes. Works good on them.

 

[RVTRKN]

bmoeller: You are right about the newer Semi's but it is good starting point for someone that does not tow a lot and asking for advise. The lite duty trucks do not have the massive weights (80K) that semi's do and 3rd gear should be fine for most, even without exhaust brakes, for our lite duty trucks. But the one rule I highly recommend is downshift before the downhill grade. With my G56 or NV5600 it is adequate in 5th and without the EB. I also don't recommend using light steady pressure because of brake fade especially our lite duty trucks.

 

[10-9jc]

While in tow/haul, turn it off and turn it back on, it will shift into 3rd and stay there until you press the accelerator.

Correct info for the '05.



Also correct - no "factory approved" EB for a 48re '05 (drat).



Another (48re) solution if it's a really steep downhill, slow down & shift

into 2nd for a while and save your brakes.



I towed my 34' 5er down (W/bd) Loveland Pass - actually went to the top on

"old" US 6 = 12K.

Used very little braking - downshifted when needed - took my time, no problem!



JC

 

[BHowell]

Thanks JC,

Good point about taking my time! I'll use 2nd if necessary.

 

[AABEN]

The jake is one good thing to have on your truck if you are running in the mountians saves the brakes