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Thoughts on transmissions? An engine combos.


FlyFishn
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I assume most here would prefer automatic transmissions. What do some of you prefer for transmissions and hp/engine?

My current work truck is a single axle freightliner 114SD, auto (39k gvw). I haven't spent much time in an auto until now and have honestly not ever given them much thought. The ones I drove a few years ago (freightliners also, cascadias from 2012-2015 MY's) drove me up a wall so I went manual and stayed there for my over-the-road truck. The auto truck I run now actually works. Its under-powered but for local use it gets the job done. I am not sure what trans is in it off the top of my head but it is a cummins engine - CNG. If the truck was diesel and had more power it would be an excellent hauler. I have 0 complaints on the transmission shifting. What I do have trouble with is getting up to speed = need more power, especially under load.

I'm just curious what some of you are running and are happy with on trans/engine/hp combos. I know a lot of the HDT RV crew runs converted used/retired over-the-road semi tractors. The older (say, pre-2017 or so) generation autos never seemed to work very well from what I experienced before. The guys in the fleet I was over-the-road with that had autos always had problems backing and maneuvering at slow-speed (why I never ran one and stuck to manuals). The contrast in the truck I'm in now (auto) is the root of my question - if it were a semi tractor with more power to run at highway speeds with as good of shifting it would be a pleasure to run. I've just never had that pleasure... Hence why I'm asking ūüėĄ

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I run a 2017 Kenworth with a 500 HP Cummins 15 liter ISX and a 13 speed Eaton Ultrashift Plus transmission. That transmission has creep mode enabled, will skip gears when shifting and do pretty much the same as any of the newer automated manual transmissions.

The new DT12 from Freightliner, the I shift and M shift Volvo and Mack, the new 12 speed Paccar in Pete's and KW's as well as all of the Ultra Shift Plus transmissions are very good and seem to be holding up well.

Edited by GeorgiaHybrid
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We have a 2005 Freightliner with a 14L Detroit and a 10 speed Ultrashift. Since ours is an older one, the trans does not skip gears automatically (you can manually do it if you want). We just use two pedals when backing up and can hitch up to the trailer without banging it in now after practice. We just use R1 even though it has an R2 also. Keeps it nice and slow. We are not in a rush, so I just let the truck do its own shifting. At 50k# total weight, we are not the fastest away from the stop light but I try not to let it bother me. Our Detroit is the larger one so fuel mileage is not as good as we could probably get with a 12.7L but the truck was nice enough with all the other items we needed so we just live with it. Sometimes you just have to compromise unless you want to order one new with the features you want. The newer automated trans are nicer and if we ever decide to get a newer truck, I would get one of them. I have no need to worry about what gear I am in and can concentrate on not hitting anything when turning and the road around me. I do like the power we have for going up the hills and the engine brake for going down! On steeper down hills, I will put the truck in manual mode and then in 9th gear usually to help keep the speed down.

Edited by Star Dreamer
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When I was shopping I talked to several mechanic friends. They all said stay away from 2 peddle autoshift. 3 peddle autoshift is pretty ok but not recommended for my farm work. 

I personally prefer an Allison. We have 4 trucks with Allison on the farm. I love them. 3 are Cummins/Allison combos and one Mercedes.

Unfortunately I have a 10 speed manual in my HDT. I chased down several trucks with Allison transmissions but they were gone before the ink was dry on the ad. 

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I have a 3 pedal autoshift and it works pretty good on the hwy.  On less favorable terrain it is a burden.  It can easily get confused on back roads.  I have learned it is best to lock out auto shifting on back roads and in certain conditions.  I have been hauling structural fill in a smaller dump trailer.  When entering the mountain hwy from the pit it is a rough sharp turn and vision is limited.  If left in auto it will usually get confused about 3/4 of the way and just drop to nuetral.  Not a good thing!  

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Keep in mind that when these semi's are pulling RV's they typically are waaay under weight as compared to when the semi was 'working'.  Basically, an underpower engine / trans combo in a working semi could be a sweet setup in the RV world.

The volvo 610 I picked up was running a Cummins ISM with the Easton AutoShift (10 speed 3-pedal).  For pulling the RV it worked awesome.  You could usually skip shift up through the gears and get rolling pretty well, in the mountains it had plenty of power for holding and accelerating as well as enough engine brake to slow it down.  Mileage was 10-13mpg which I was plenty happy with.  But, the Cyclone and toys wasn't 30k lbs in total, so the load was pretty light.

I didn't want for more power, I wouldn't search out an ISX for example.  Getting into a 2-pedal transmission would be the next step.  The class A pusher we also spend time in has a 2 - pedal Allison behind one of the huge Cats, it makes for a very pleasant driving experience.

 

 

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One of the line-in-the-sand things for me on my truck was I wanted the iShift.  In the vintage trucks that I could afford this was the best transmission, from my research.  They skip up and down, allow for feathering to hook to the trailer and had a fairly proven track record.

Every "mechanic" and "professional driver" I spoke with during my research phase told me that these were junk and would be nothing but trouble as would the Volvo engine.  

I found a nice, clean 2012 Volvo 730 with a D13 engine mated to a non-overdrive iShift (2.47 rear).  This truck was at a price point that worked for me and thus far I am very happy with the truck.  It is tuned for the "Ecco-torque" package which is 435 hp and dual torque ratings.  1750(?) for 1-10 gears and 1650 (?) for 11-12.  Pulling my trailer I have never been want of any more power.  The transmission operation is excellent and the way it works with the engine and engine brake are very well designed and seamless, IMO.  So far I had to replace the starter (cost less than my VW's starter) and a hard pipe in the DEF system.  Other than that there have been no problems in the ~25k miles I have put on it.

The 40-year, multi-million mile professional driver that went with me to bring the truck home was very impressed with the truck.  The way it drove, rode and the way the cab/sleeper was set up he said was far better than any of the company trucks he ever drove.

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All of the modern fully automated transmissions work acceptably well. Some are more refined than others, with (arguably) the IShift being the most refined. I think I've driven every one of them except the newest model year PACCAR MX version. They all work fine. I like the shifter on the column that both FL and PACCAR do. It is very convenient and very intuitive. The dash shifter on the Volvo is OK, and is easy to use, but not as easy as the column shifters. Any shifter seat mounted is last on my personal list. It is simply in the way, and unnecessary. In RV use you will RARELY use the shifter after starting - virtually never. So the utility of it on the seat-side is questionable in my mind. But that is  a personal preference as much as anything.

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On 2/20/2021 at 9:13 AM, Star Dreamer said:

We have a 2005 Freightliner with a 14L Detroit and a 10 speed Ultrashift. Since ours is an older one, the trans does not skip gears automatically (you can manually do it if you want). We just use two pedals when backing up and can hitch up to the trailer without banging it in now after practice. We just use R1 even though it has an R2 also. Keeps it nice and slow. We are not in a rush, so I just let the truck do its own shifting. At 50k# total weight, we are not the fastest away from the stop light but I try not to let it bother me. Our Detroit is the larger one so fuel mileage is not as good as we could probably get with a 12.7L but the truck was nice enough with all the other items we needed so we just live with it. Sometimes you just have to compromise unless you want to order one new with the features you want. The newer automated trans are nicer and if we ever decide to get a newer truck, I would get one of them. I have no need to worry about what gear I am in and can concentrate on not hitting anything when turning and the road around me. I do like the power we have for going up the hills and the engine brake for going down! On steeper down hills, I will put the truck in manual mode and then in 9th gear usually to help keep the speed down.

I have an 06 with same setup. Does great but mpg is lower than most I read on here. I get 7 mpg. Still better than the dually pulling our Teton.

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I have very limited experience with this topic but I the D13 engine mated to a non-overdrive iShift (2.47 rear).  

I have only put about 1000 miles on it so far with no towing yet.  The skip shift feature is awesome.  It shifts as well as my 2016 Chevy dually.  While it is not as "fast" as my Chevy, it will get right up to speed if I want it to.  

My dad who has been driving manual trucks all of his life came down to inspect the truck when I bought it.  He was very impressed with how it worked also.

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I got the specs off my truck's stickers today. Its a cummins 320hp engine (CNG) mated to an Allison 3000 RDS trans (freightliner 114SD, 39k gvw). I have not played with the different trans modes but I do know I can run it in simulated manual. I have never messed with it, though, so I am not sure if it will allow skipping. I will say the only nuance of note is the brake pedal has to be pressed for it to shift between f, n, r. I do a lot of forward/backward cycles and sometimes that doesn't sync well (operator error/ergonomics, not the transmission). I doubt that would ever be a concern in any other service though.

 

The truck is pretty slow. I'm not sure if being CNG is why it is as sluggish as it is, or if its the HP, so that was what prompted the thread - to get some input from others. It is interesting to get some experience with different trucks/equipment and have that to lean on later.

 

Some in the thread mention the feathering ability when hooking up. I can see where that would be an important point. Though I had to bump a lot of semi kingpins hard at times to get the hook to latch in some other trucks. I wouldn't want to hit a lighter trailer like that, though - purposefully or not. I have to maneuver my current truck in tight spots most of the time I'm running it and have 0 problems with precise forward/backward positioning. Another nice thing I've come to enjoy about the rig.

 

I did some poking around our fleet and we have some newer trucks with M2 Business Class on the side. I assume they are 112's, I can check the spec stickers. I believe they are CNG also.

 

While digging in to pulling rigs before one of the usual comments with the M2-106, and I thought the M2-112 also, was how "small" they were inside. I did have to run out a couple weeks ago in an older International (2000-2005 vintage) that was definitely a smaller cab (don't know what model or gvw, but it was a heavier medium duty - class 5 or 6 maybe) for a few hours and it was definitely tighter in there - fine for what I was doing and the time I was in it, but that was a good reality check. My 114SD and over-the-road truck (2018 International LT), speaking of the front of the cab (114SD is a day cab, LT was a mid-height sleeper) they are pretty much the same size.

 

If I am correct - registration and vehicle class go off of the axle weights, which in turn adds up to the gvw (like my work truck is 16k front/23k rear = 39k combined). So from an ownership perspective (reg, ins) it wouldn't matter what size the cab was or how long the wheelbase was - just the weights are what count.

 

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16 hours ago, FlyFishn said:

The truck is pretty slow. I'm not sure if being CNG is why it is as sluggish as it is, or if its the HP, so that was what prompted the thread - to get some input from others. It is interesting to get some experience with different trucks/equipment and have that to lean on later.

 

While digging in to pulling rigs before one of the usual comments with the M2-106, and I thought the M2-112 also, was how "small" they were inside. I did have to run out a couple weeks ago in an older International (2000-2005 vintage) that was definitely a smaller cab (don't know what model or gvw, but it was a heavier medium duty - class 5 or 6 maybe) for a few hours and it was definitely tighter in there - fine for what I was doing and the time I was in it, but that was a good reality check. My 114SD and over-the-road truck (2018 International LT), speaking of the front of the cab (114SD is a day cab, LT was a mid-height sleeper) they are pretty much the same size.

 

The lack of power is due to it not being a diesel, and likely a relatively smaller engine at that.  A gasoline, propane, or CNG fueled engine just won't make the torque of a comparably sized diesel, due to the lower energy content of the fuels used, and horsepower is simply a function of the available torque at a given RPM.

An M2-106 is a medium duty truck, just like those old Internationals that they have there.  An M2-112 is neither fish nor fowl, or both, depending on how you look at it.  They're Class 7 trucks, which makes them an HDT, and the longer hood allows the use of some HDT-class engines, but they're still based on the "M2 Business Class" medium duty cab, so it shares the M2-106's shortcomings relative to a true HDT cab -- like the additional room and over the road creature comforts.

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