Question on differentials/power dividers and "2 speed rears"

Hi Folks, as a newb here, just getting BACK into the industry (I pulled a lowboy for an excavating company from the early 80's to the mid 90's, and my ears are STILL ringing from that &#&$* 8v-71!). Anyway, the first tractor I drove was a 1962 Ford T850 pulling a 43 foot lowboy trailer with a 534 gasser and a 5 speed tranny and this weird, 3 position, electric-to-air splitter that worked as such: Run 1-5, then back up into 2 with the splitter up to the middle, then top then 3middle,top....Exactly like a 13 speed with a 3 position handle, except here's the difference: When you split to the middle, it shifted the front diff into high gear, and put the rear diff in neutral. When you split to the top, it would put the front diff into neutral, and engage a taller gear in the rear diff. So, in effect, once you got out of low range, you were only driving with one differential/axle at a time. The system worked FLAWLESSLY! By about 1984, we "updated" to a '73 LT9000 with a 318 detroit (with dual exhaust, putting one of the LOUDEST mufflers ever made next to your ear) and a REAL 13 speed(and over a million miles). Lately, I've been seeing late-model tractors for sale with 9, 10, and 13 speed trannies AND "2 speed rears" .

Here's my questions:

• Do most late model tractors have the traditional layout of two rear differentials, and a power divider on the front diff.?
• And are there some trucks out there with tandem rears, but only ONE diff actually being driven, and the other axle is "dead" (there just to carry weight) even though they LOOK like both are drivers?
• What's the deal with the newly found popularity of 2-speed rears in today's trucks (I think I know the answer, I just want to hear it from someone else.)
• I guess what makes matters more confusing is that in the for-sale papers, every once in a while, an ad will say "twin screw" which I was under the impression ALL tandem-axle trucks were?

I know that to some these might sound like stupid questions, but at this point, I don't know, so I'm asking for an explanation of what's out there these days. Any help will be appreciated. Thanks!!

 

So, that means a "twin screw" is basically a conventional, tandem axle drive system, with a power divider?

 

Yes, I was using the word "conventional" meaning "normal" or "standard" I'll refrain from making this a "who's on first" conversation.

So, by $ I'm guessing you're referring to initial cash outlay? That's one HIGH number there for your low range! So, just so I know about a setup like yours, what engine and tranny do you have up front? And do you actually shift those rears while rolling, or select based on the task at hand and leave them? Thanks, this kind of info is good to know for when I go truck shopping in a year or two.

 

So, first off, what's the TYPICAL engine/tranny setup for these heavy haulers? I see ads on ebay for 700-1000 hp cat engines all the time, but I would surmise that these are NOT work engines but rather competition engines for those with the means to own a pulling truck. There's also a truck shop I saw on TV that typically puts 800hp Cat 3406's in their custom trucks that actually WORK daily hauling gravel. Sounds to me like if a gravel hauler in Texas can afford to spend close to a quarter-mil on his tractor, THAT'S the place to be!!

Either way, Heavy-Haul is where I would like to be in about 1-1/2 to 2 years. I figure that's how long it will take me to 1. actually get a job running flatbed. 2. Do that for a year, and, near the end of that year, start my move toward heavy haul. I live a short distance from 2 major heavy haul trucking firms (one is ATS-Anderson trucking), plus a bunch of smaller outfits. Then 3. Work my tail off to get the education and experience to be part of one of the "go-to" teams for the REAL big stuff, think windmill blades, bridge beams, skyscraper steel. THAT'S my ultimate goal. 650HP, pulling 12 or so axles......could happen, especially with the help of fine folks like you all in this forum