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Post by prairieboy on Feb 12, 2021 10:46:27 GMT -6
Wondering for those who might know what specs are needed in a truck pulling super bs. We broke an axle taking off in a field so are realizing that 46,000 are needed but we also find it hard to hold 100k with a 475hp C15.
We also are noticing a lot of automatics popping up in the used market and are wondering if they are reliable. We chase enough electrical problems all over the farm without adding to them.
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Post by torriem on Feb 12, 2021 11:33:35 GMT -6
My cousin bought a bunch of Volvo trucks with 500 HP D16 engines and the iShift 10-speed transmission. Says it pulls just fine on the highway and also doesn't seem to have trouble in the fields, although they often use manual mode to lock the transmission down in soft fields.
We're looking at a used Kenworth with a 18-speed ultrashift. I've driven an 18-speed ultra before with a B train and it pulled nicely and was a pleasure to drive.
I definitely think a 3.9 or greater rear ratio is better. I wouldn't want a truck under 500 hp either.
How much would it cost to replace your axles with 46,000 lb and a taller ratio? Bet it would be cheaper than a new truck. And the 475 hp will pull better with the steeper ratio.
I suspect you'll have more problems with emissions on newer used trucks than the automatic-shifting transmission.
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Post by meskie on Feb 12, 2021 12:02:06 GMT -6
What you need and what you want to pull super b are 2 different things.
For me 475hp with 3.90-4.10 rears super 40s with an 18 speed would be what I would like.
I’ve pulled lots with 430-470 Detroit and a 13 speed with regular 40s.
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Post by prairieboy on Feb 12, 2021 12:16:35 GMT -6
We have zero tolerance for emissions problems on our farm. Anything that arrives on the yard with emissions junk on it gets deleted immediately. We just price it into used equipment that we buy.
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Post by northernfarmer on Feb 13, 2021 18:32:05 GMT -6
I've never owned a super b to have the experience with them, did pull a "b" train a bit years ago with an old beast of a truck although only on frozen ground to the elevator but mostly pull a tridem which of course gets overloaded during harvest from the field to the bins. Even with a tridem trailer and loaded right up, that is going to tax a truck that isn't geared properly and a real risk of bad things happening in the diffs if they are too light. You never mentioned what type of truck this is, vintage etc and what transmission, diff series and ratio, tire size etc.
Here's an example of one neighbour who had bought a truck ( have not asked lately if they still have it or got something else ) that has 40 rears with 3.70 gears, 24.5 tires, 18 speed and I presume the ISX cummins series. Soon after pulling one of their super b's the front diff failed and not sure if it was the gears or the internals of the carrier that failed but had to get a reman third member. Then .... the rear diff failed, again another reman. Then the splines on an axle of the front diff along with the splines in the side gear let go and apparently cost as much or more then a reman to repair so once again another reman in the front diff. Like I said, don't know the continuing saga of that truck but upon putting the second diff into the front they replaced all four drive axles. The gearing, due to the failures ( hind sight is always 20-20 as they would have installed lower gearing had they known how it would all play out ) they still had 3.70 gearing which is crap for pulling a super b as the engine is barely running at legal highway speed if one insists on putting it into 18th and have any slight grade or head wind. They also replaced the clutch at least once which again goes back to too high a gearing for lifting the load in anything but perfect ground as it can only take so much abuse.
It used to be some 20 plus years ago that 46000 rears and 4.10 gears with 475 hp and an 18 speed was considered the on highway super b spec but then with some newer engines and electronics the 3.90 or so ratio seemed to be common as well but then hp and torque was going up as well. But I think the fact remains those specs are seen more as highway type specs and not off road as part of the picture for that type of weight.
One of my trucks and the one that mostly pulls the tridem trailer has the C15 rated at 550 ( unfortunately it is an acert but does not have the other crap that killed the cat road engine market ) , 18 speed manual, 46000 rears, 4.30 ratio, 4 way lockers, 24.5 tires. For the haul distance I do I quite like it,yes the engine is turning over faster if one chooses to cruise along at 110 empty but loaded I quite like it over all for the tridem. Can still get some speed out of it for running a hill as well. Its hard to have a truck that is spec'd perfectly for easier flat type highway hauling and also has really tall legs for puttering along swiftly when empty at high speeds and yet good to lift a load in a field, its a compromise it seems.
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Post by northernfarmer on Feb 13, 2021 21:19:12 GMT -6
Here is a calculator for figuring out engine speeds at various ground speeds with the chosen tire size/gear ratio. Some constants have to be figured out first as per the tire size in looking up in tire information for the tire fitted to the truck if one wants to be accurate, and having the gear ratios for the transmission. But once one has those numbers its fairly straight forward to work with some comparisons between various choices of axle ratio and how that would look at whatever speeds chosen, or lets say it was 17th gear ratio and knowing what to expect for speed ... can you maintain 100 km as an example and at what rpm. Its what I did when figuring out what I thought best fit my goal and not be surprised by assuming things and realize something else once behind the wheel.
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Post by northernfarmer on Feb 14, 2021 9:42:19 GMT -6
Here is a brochure of the Eaton 18 speed with gear ratio chart for the manual transmission. I have no experience with automated manual transmissions to comment there other then reading about struggles with two pedal trucks and zero control over what the clutch is doing and getting stuck as a result as the computer takes over and if the gearing isn't low enough your looking for a pull if on the wrong surface, I know I sound negative on those transmissions and perhaps that isn't justified but am a bit leery of them, I would like to try one sometime with a load in a real scenario as driving an empty truck doesn't tell much. Tire diameter, that sure varies by brand and tire model up to an inch difference it seems within the same tire size. Having said that to give a reasonable number to work with I'll suggest these measurements , for 11R-22.5 use 42" diameter, and for 11R-24.5 use 44" diameter.
So as an example I'll use the truck I mentioned of mine with the 4.30 diff ratio and its 18 speed and its 24.5 tires. Using the calculator and wanting to to know the engine rpm at 100 km in top gear which is .73 ratio, it takes a few trials with the rpm box to get close to that 100 km ( 62.14 mph ) speed as unfortunately this calculator doesn't allow to put the ground speed in to calculate engine rpm, never the less its not bad to work with and not use the formula method on paper. In this example I come up with 1490 rpm. Another example as per my comment about 17th gear so using the .86 ratio, that computes to 1760 rpm at 100 km. In fact with this 4.30 ratio even in 16th gear which is direct at 1.00 ratio at 100 km the engine is turning over at 2050 rpm which of course is not how one would drive normally but it goes to demonstrate what gear choice flexibility one has with a certain chosen differential ratio and transmission/tire size combination on paper.
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