In a lot of farm trucks and grain trucks, you will find a split rear to change the final drive ratio between gears. Why, with todays technology, do you they not offer a split rear in superduty trucks? A 3.55 ratio for un loaded, and 4.88 when towing. We have electronic locking rears, why no electronic split rear.
Why no split rears?
- OP 🔹 Shorebilly Farmer
- Start date
$$$
The average consumer would have no clue what a 2 speed axle was and definitely not when to use it. The increased customer service load from people leaving it in the low gear and ruining their fuel mileage would offset any extra sales it might make as well.
Extra complexity of manufacture and maintenance is also not worth it.
Most farm and grain trucks will never be heavy enough to even really need a 2 speed drive axle. I'd imagine a lot of those tractors are repurposed heavy haul trucks that were bought used. The heavy haul tractors would have much stronger frames for off highway use along with the higher power engines. The only time they might need it would be to really come to a crawl to match some other piece of equipment or dealing with some truly terrible ground conditions.
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1200 lb/ft and a 10-speed + a transfer case, these being 4 X 4s.
Or, in the Godzilla's (w/ a good aftermarket exhaust, 500 lb/ft) situation, 4.30 axles, 10-speed and a transfer case low range.
don't need no split axle.
I'd like one, though, just because I think they're cool. I've driven plenty of them.
Or, in the Godzilla's (w/ a good aftermarket exhaust, 500 lb/ft) situation, 4.30 axles, 10-speed and a transfer case low range.
don't need no split axle.
I'd like one, though, just because I think they're cool. I've driven plenty of them.
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They're 
correct! It makes sense on paper, but the short answer is that modern transmissions and engine torque curves have completely eliminated the need for a split rear end. Plus, the fact that most Super Duties are 4x4 makes it virtually impossible to implement.
Back in the day of grain trucks, you had a 4-speed or 5-speed manual transmission. The RPM drop between gears was massive. A two-speed rear axle effectively turned a 5-speed into a 10-speed so you could keep the engine in its narrow powerband.
Today, your Super Duty has a 10-speed automatic (the Ford 10R140). First gear is a super-low 4.61:1, and 10th gear is a massive 0.63:1 double-overdrive. Because the transmission has such a wide gear spread, it already provides all the mechanical torque multiplication you need to get 30,000 lbs moving, while still letting you cruise unloaded at 75 mph at low RPMs.
Most modern Super Duties are four-wheel drive. If you had an electronic split rear end that switched from 3.55 to 4.88, you would also need a split front differential that switches at the exact same time.
If the front and rear axles aren't matched perfectly, the moment you put it in 4WD or 4HI, the driveline would bind up and literally shatter the transfer case. Engineering a synchronized two-speed front and rear axle system would be incredibly complex and highly prone to failure.
Old farm trucks had naturally aspirated diesels or low-compression gas engines with very narrow powerbands. If you didn't keep the RPMs in a tiny 500-RPM window, you couldn't pull a hill.
Modern engines like the 6.7L Power Stroke or the 7.3L Godzilla gas engine produce massive, flat torque curves across almost the entire rev range. The computer manages the engine and the 10-speed transmission to always keep you in the power, completely negating the need to manually split gears at the axle.
A two-speed rear differential requires a heavy, complex planetary gearset inside the differential housing. Adding this to a modern truck would:
1. Massively increase the unsprung weight of the rear axle (ruining ride quality).
2. Introduce more parasitic drivetrain loss (lowering MPG).
3.Require more specialized maintenance.
4.Add thousands of dollars to the sticker price.
Automakers realized they could solve the heavy-hauling problem much cheaper and more reliably by just adding more gears to the transmission!
correct! It makes sense on paper, but the short answer is that modern transmissions and engine torque curves have completely eliminated the need for a split rear end. Plus, the fact that most Super Duties are 4x4 makes it virtually impossible to implement.Back in the day of grain trucks, you had a 4-speed or 5-speed manual transmission. The RPM drop between gears was massive. A two-speed rear axle effectively turned a 5-speed into a 10-speed so you could keep the engine in its narrow powerband.
Today, your Super Duty has a 10-speed automatic (the Ford 10R140). First gear is a super-low 4.61:1, and 10th gear is a massive 0.63:1 double-overdrive. Because the transmission has such a wide gear spread, it already provides all the mechanical torque multiplication you need to get 30,000 lbs moving, while still letting you cruise unloaded at 75 mph at low RPMs.
Most modern Super Duties are four-wheel drive. If you had an electronic split rear end that switched from 3.55 to 4.88, you would also need a split front differential that switches at the exact same time.
If the front and rear axles aren't matched perfectly, the moment you put it in 4WD or 4HI, the driveline would bind up and literally shatter the transfer case. Engineering a synchronized two-speed front and rear axle system would be incredibly complex and highly prone to failure.
Old farm trucks had naturally aspirated diesels or low-compression gas engines with very narrow powerbands. If you didn't keep the RPMs in a tiny 500-RPM window, you couldn't pull a hill.
Modern engines like the 6.7L Power Stroke or the 7.3L Godzilla gas engine produce massive, flat torque curves across almost the entire rev range. The computer manages the engine and the 10-speed transmission to always keep you in the power, completely negating the need to manually split gears at the axle.
A two-speed rear differential requires a heavy, complex planetary gearset inside the differential housing. Adding this to a modern truck would:
1. Massively increase the unsprung weight of the rear axle (ruining ride quality).
2. Introduce more parasitic drivetrain loss (lowering MPG).
3.Require more specialized maintenance.
4.Add thousands of dollars to the sticker price.
Automakers realized they could solve the heavy-hauling problem much cheaper and more reliably by just adding more gears to the transmission!
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