New truck!

[Heavymetal]

We are heading down to the Western Star dealer Saturday to start the process all over again. We will be ordering a new 2018 5700XE and I was wanting a little feed back on gearing for the rear end and H.P. We will be sticking with the tandem axle super singles like we are running now, but was thinking of moving from the 15 liter to the 13 and going to the 2:41 rears instead of the 3:08. Is anyone running a higher geared rear end and if so how do you like them? I am also looking to extend the wheelbase from 230" to around the 245" range and extend the frame rails by about 18" this would give us the same bed length we have now with a little more wheelbase which I like. 

 l would like some input on brakes. Drum or Disc! We have had both and are running antilocke disc at this time, but I haven't really noticed a big difference between the two on the class 8 trucks, not like I did on a LDT. Who else has disc and do you notice a big enough difference to justify the added cost? 

 Transmission gearing for the weights that we tow! I remember seeing a chart are something that showed the gearing and speeds for the best truck performance, I am dreaming are did someone have a chart like this. 

 I would like to make this the last truck we buy so any input would be appreciated. 

Of course this means Pathfinder is going on the market so if you know someone looking for a 2016 truck with under 100k send them my way. 

 

Thanks for the help 

Richard

[RickS]

Hi Richard....it was nice meeting you at the ECR. If I was specing a new truck the air disk would be a must have. The stopping distances are well published on these trucks. Also, the disks have less to worry about as far as checking for proper adjustment. Don't know the sweet spot for your engine but I'm very happy with 2:64 I ordered and would spec that gear again with the current i-shift overdrive ratio.

[Shawn Patterson]

8 minutes ago, RickS said:

Hi Richard....it was nice meeting you at the ECR. If I was specing a new truck the air disk would be a must have. The stopping distances are well published on these trucks. Also, the disks have less to worry about as far as checking for proper adjustment. Don't know the sweet spot for your engine but I'm very happy with 2:64 I ordered and would spec that gear again with the current i-shift overdrive ratio.

 

I am running the 2.64 as well with a Volvo D13 @425 HP.  RPMs are low when I am cruising along at 65 MPH.  Pulls our DRV 43 Atlanta well.

[Heavymetal]

22 minutes ago, Shawn Patterson said:

I am running the 2.64 as well with a Volvo D13 @425 HP.  RPMs are low when I am cruising along at 65 MPH.  Pulls our DRV 43 Atlanta well.

I agree. We had the 2:64 in our Cascadia and I thought it did a good job. I have been doing some research and see that on most of the fleet trucks the DD15 is rated at 400HP with 2:41 rears on a 6x2 setup instead of a 6x4. 

[Heavymetal]

34 minutes ago, RickS said:

Hi Richard....it was nice meeting you at the ECR. If I was specing a new truck the air disk would be a must have. The stopping distances are well published on these trucks. Also, the disks have less to worry about as far as checking for proper adjustment. Don't know the sweet spot for your engine but I'm very happy with 2:64 I ordered and would spec that gear again with the current i-shift overdrive ratio.

Was your last truck drum? We had antilocke drums on our Cascadia and I really have not noticed a difference between the to other then the pedal travel. 

[Steve from SoCal]

Disc brakes really earn their keep on vehicles that use brakes at high frequency cycles.   The heat dissipation and clamping geometry of disc brakes are the key features.     A vehicle that travels on highways with few stop/start cycles would see the least benefit, traveling the Rockies, Sierras or, Cascades the most.    

The total vehicle weight is another factor, at typical RV weights either disc or drums will do fine 95% of the time.    Hot cycling of the brakes is where the disc brakes shine, with engine braking and light weight the disc's loose some value.  Personally; given the choice I would opt for disc, better system, with as mentioned fewer critical inspection/adjustment points.

 

Steve   

[NoDirectionHome]

Quote

 was thinking of moving from the 15 liter to the 13 and going to the 2:41 rears instead of the 3:08

Is your DT12 not an overdrive?  If so you are already running 2.41 final ratio.  The 2.4's you see are direct drives.  
I have 6 wheel anti-lock discs and like them.  They will pay for themselves at the 1st brake pad change (YOU can do it in 10 minutes) and in re-sale value.

I have the tire size/gearing/speed spreadsheet if you message me your e-mail

[GeorgiaHybrid]

Make sure the dealer gives you a breakout of the gearing with the speed and rpm in each gear before you make your final choice. With ours, a 3.07 rear with a double overdrive 13 speed lets me loaf along at 1220 rpm running 65 in 13th and hits the sweet spot on the ISX (1400 rpm) at roughly 73 mph. 12th at that 1400 rpm range is right at 65 mph and 11 (direct drive) is right at 55 mph running that same 1400 rpm.

 

The dealer should be able to help you out with 2 or 3 "what ifs" and let you decide the best given the engine choice and speed you want to run at. Make sure the engine you choose has the torque curve in the right place for the speeds you plan on running.

[RickS]

3 hours ago, Heavymetal said:

Was your last truck drum? We had antilocke drums on our Cascadia and I really have not noticed a difference between the to other then the pedal travel. 

Our last truck (Freightliner) had 4-way disk brakes as well. Just can't see going back to drum brakes myself.

[Heavymetal]

2 hours ago, GeorgiaHybrid said:

Make sure the dealer gives you a breakout of the gearing with the speed and rpm in each gear before you make your final choice. With ours, a 3.07 rear with a double overdrive 13 speed lets me loaf along at 1220 rpm running 65 in 13th and hits the sweet spot on the ISX (1400 rpm) at roughly 73 mph. 12th at that 1400 rpm range is right at 65 mph and 11 (direct drive) is right at 55 mph running that same 1400 rpm.

 

The dealer should be able to help you out with 2 or 3 "what ifs" and let you decide the best given the engine choice and speed you want to run at. Make sure the engine you choose has the torque curve in the right place for the speeds you plan on running.

My rpm's run in the range of yours. I see my best fuel economy at about 72 mph. 

[GeorgiaHybrid]

One other thing that almost everyone else has mentioned, order the truck with disk brakes front and rear. You will regret it sooner or later if you go with drums. The brakes feel entirely different and the stopping distances are proven to be a significantly shorter than drum brakes.

[Heavymetal]

33 minutes ago, GeorgiaHybrid said:

One other thing that almost everyone else has mentioned, order the truck with disk brakes front and rear. You will regret it sooner or later if you go with drums. The brakes feel entirely different and the stopping distances are proven to be a significantly shorter than drum brakes.

That's what I have now antilocke disc vs my last truck antilocke drum. I just haven't notice a huge difference but as mentioned earlier when it comes to a brake job the diff is huge. If you get a chance PM your gearing specs so I can compare them to what I have now. I know that after all the conversation at the rally that my real MPG are better then what most are getting. I would really like to find about 400 miles of flat ground with no wind to see what is really possible on the MPG. We were running 9.2 on the way home and then dropped to 8.2 average when we hit that storm in MS all the way to Houston, wind square on the nose blowing 20 gusting 40 with rain from hell. We sit on I10 for two hours waiting for them to up right a semi that hydroplaned and ended up on its side. I will say that the guys on the CB were playing hell with the young drivers about hydroplaning a semi and when it turned out to be a Volvo they turned up the heat. I did learn that the older drivers don't like volvos, not one bit. 

[Jack Mayer]

What David said (Georgia) is important. Work backward from your expected speed and gradient information and then select the gearing to match it - either with an overdrive trans, or direct. The simulation programs the dealer has should be able to get it spot on. But you have to start with your speeds and load. That will get your hp settings and gearing right.

As an example, in my truck I have a 2.67 (XE package). It cruises in 12th at 1150 rpm and at 68 mph (or 67). That  is faster than I normally drove in the past, but if I go any slower I drop to 11th at closer to 1400 rpm. It does make a difference. Plus if I stay close to the "edge" of 11th it will downshift on anything more than a 3% gradient. So you have to work the numbers. I'm happy with this behaviour, but if you REALLY want to drive this particular truck slower then you would be unhappy. You would either be hunting gears, or running in 11th. It is really important to run the simulation or use the tables. The dealer should do that as a matter of course.....

Air disc for sure. for all the reasons stated.

[RickS]

Richard,
Also your Hp/TQ spec will make a difference on whether the truck is hunting or down shifting more frequently. I have the 500/1850 spec 13L engine and it takes a fair grade before it shifts into 11th gear. The lower HP/TQ spec you have the faster you will slow down and the truck will downshift sooner. 

[Exile]

My trucker uncle had a friend that put an 18 speed behind a ten speed.

he had the right gear for every speed, but apparently had trouble finding it, as he went back to a 13 speed.

Might not work so well with a computer shift rig  i assume you want a two pedal?  Or a u-grind?

 

rear end?  Its all final drive ratio, and the gear you want to drive in.

 Tenth and 17th?

[rickeieio]

A neighbor had a stretched single axle White dump truck, 250 Cummins, 10 spd.  He added a 3 spd, auxilliary behind the 10.  Under, direct, and slight OD.  It was pretty slick in it's day, early '70s.

[Scrap]

Disc and RSD drum are pretty comparable on the first stop and most of the 2nd stop, then they diverge quite a bit from there.  Since you drive with your ACB doing the work you are definitely better served with disc.  Just like we talked about in the other thread, for a go-anywhere, do anything, forever truck I have a hard time going with all the 6x2's, direct drives, dry sumps, etc, etc  It does work and it does save fuel, but just like super 10's, Lightnings, RTX's, etc, etc, it is just the current thing of the freeway flyer and it's time will also pass.  A lot of them are pavement only hub to hub application restricted as well.  A forever truck's gotta be an OD, and enough deep reductions to get more places than just an on-ramp.  Then again I don't spend much time in the midwest either and it is a whole different ball game out there.  Anyways, think real hard about not doing it....

Aftertreament totally changed for 2017 so I suspect most of your decisions will end up being around figuring out the frame layout.  I don't know much about Daimler, but ours it is totally different than last year and I suspect your new truck will lay out quite a bit different from your old truck.  So leave yourself enough time to get that figured.  Also with us a whole lot of the truck changes this October, which is later than normal.  So check close on what they got coming out and don't order too early...

[NoDirectionHome]

Daimler GHG'17 is still the one box.  Same size as previous.

[Heavymetal]

23 hours ago, RickS said:

Richard,
Also your Hp/TQ spec will make a difference on whether the truck is hunting or down shifting more frequently. I have the 500/1850 spec 13L engine and it takes a fair grade before it shifts into 11th gear. The lower HP/TQ spec you have the faster you will slow down and the truck will downshift sooner. 

When I first got the WS I had it tuned to 505/1850 and went back down to 455/1750 which I like better. When it comes to down shifting the adaptive cruise worries about that on down hill runs but on the level it goes in to Eco mode and auto coast so I have not even paid attention to when it down shifts. So far it has all worked very well. 

[Broncohauler]

RV hauler peterbilt has drum brakes, my work truck Volvos have allwheel disk and so will our new trailers. 

There is a big difference but if your only thinking cost of a brake job. My peterbilt went 900,000. Miles before it needed brakes. You'll probably never do them. 

[Tahoe Shark]

I might have missed it, but why are you ordering a new truck when you just bought the 2016? What about the 2016 do you not like? Just asking to gain some knowledge about what not to do.

[GeorgiaHybrid]

Richard,

 

Send me a PM with your email address and I will send you a copy of the hill start grade ability, speed ranges in gears, max grade at different rpms in each gear at max weight and several other charts that you will need to get from your dealer to determine what type of gearing you would like.

[Sculptor]

On 5/12/2017 at 1:46 PM, Tahoe Shark said:

I might have missed it, but why are you ordering a new truck when you just bought the 2016? What about the 2016 do you not like? Just asking to gain some knowledge about what not to do.

I'm currently evaluating the impact my prospective used truck will have on our future.  Agonizing maybe?  I also wonder what might cause me to trade up after only a year or 2.   

[Sculptor]

I forgot to ask, have you decided on an asking price for the old worn out 2016 truck?    

[Heavymetal]

On May 12, 2017 at 0:46 PM, Tahoe Shark said:

I might have missed it, but why are you ordering a new truck when you just bought the 2016? What about the 2016 do you not like? Just asking to gain some knowledge about what not to do.

First of all we love our WS! I am just wanting to make a few changes to the truck and instead of spending the money to lengthen the frame and change the color to the 2016 I had rather just spend it on a new truck and let the factory make the changes for me. We will be ordering the same truck in a color that matches our RV and will go to a 245" wheel base instead of the 230" we have now, plus a few other small personal tweaks that my wife wants.