DT12 vs 13 speed

You will not get 2 miles per gallon better just because it's a automatic. It all depends on the nut behind the wheel.

 

It's a TennMan special.......

 

Seen an auto Schneider jackknifed on I80 near Wamsutter WY a week or two ago. Behind him was what appeared to be 2 other jackknifes responding to him and another two drive offs. It was a straight downhill stretch wide open visability. Must have slammed on brakes for some reason. I don't trust autos especially on ice and downgrades.

 

I have the DT12 currently. It's great most of the time.

Things I don't like is if it is in Auto mode and i turn on the Jakes by moving the shifter toward me 1, 2, or 3rd postion, the truck wil violently begin downshifting and jaking if you take your foot off the pedal. So going down a mild grade for example, in a manual you just flick on the jakes or they are on all the time either way it is still in the gear you want.

I have seen this thing go from 12th, to 11th to 10th and then 9th and jump all the way up to 2200 rpms violently trying to slow the truck down with the jakes.

What I have to do is set it to manual and downshift to 11th then put on the jakes. oh and cannot have the jakes on and cruise on at the same time. They have what's called IPM where you set the cruise speed and the jakes will automatically hold the truck back 2 miles per hour above your set speed. What it really does is gets about 8 miles per hour above set speed then aggressively downshifts and throws the rpms into 2200 screaming the engine. Last thing you need in the rain or snow or a downhill curve. j

I saw one of my colleagues with the same make/model as mine stuck on a little icy bunny hill in New Mexico blocking the entire freeway behind him. Gotta make judicious use of that Manual which kills the whole purpose of the increased fuel economy of the Auto. I don't see it anyway, I'm tracking 6.4 miles per gallon, had the truck one month, 13,000 miles so far.

Where it is supposed to shine is ECoast. So on a slight flat or downhill the truck engine will slack off to 500 rpms, you lose all torque for a moment and thetruck drifts to the side of the road. Correct to center and boom it re-engages at 1400 rpm for a moment and throws the truck to the other side of the lane.

All those things are like a wonderful oiled up nuru massage compared to when it comes time to back up between two trucks. Lurchy, jumpy, speeds up way too fast at the wrong moment. Where you used to do one pullup, you now do 12 pullups.

 

From my understanding Schneider disables every setting except economy mode on their autos. So much for using the jake brake. Actually now that I think about it that's probably exactly what happened. Driver had jake on and it violently downshifted and threw him into a jackknife. Either that or ECoast. ####ing stupid ##### at Schneider disable manual mode, but I know, never use the jake in slick conditions... blah blah blah

 

My assigned cummins isx15 runs 65 governed mph at 1185 rpm with 10 speed auto that .80 small step drive, 2.64 rear axle, and 275/85r22.5. Not a good package because of that auto Tranny that acts up with sensor failures even when it's new.