Why 3.73's for HDPP??
01-17-2018, 10:19 PM
#41
Ron:
1st: I need to correct a mistake & misconception - 35mph is for dualies; 40mph is the limit for 1/2 tons, sorry about that. But the speed limit on Route 68 is 55mph and trucks are expected to try their best to attain it. So, the HDPP truck isn'tallowed supposed to back off and just run same speed as Max tow, if it can run up to speed limit, it is supposed to try.
2nd: I don't have the the latest version of the spec and SAE found they had to better define the trailer along the way. Without the details of the trailer I can't give you the exact load numbers and my current job won't allow me to update my version except on my own dime and I don't need it that bad.
The 3k' of elevation gain on 100*F day rally punishes N/A engines - Nissan XD does better than the F-150 5.0, so it's rating isn't that conservative.
1st: I need to correct a mistake & misconception - 35mph is for dualies; 40mph is the limit for 1/2 tons, sorry about that. But the speed limit on Route 68 is 55mph and trucks are expected to try their best to attain it. So, the HDPP truck isn't
2nd: I don't have the the latest version of the spec and SAE found they had to better define the trailer along the way. Without the details of the trailer I can't give you the exact load numbers and my current job won't allow me to update my version except on my own dime and I don't need it that bad.
The 3k' of elevation gain on 100*F day rally punishes N/A engines - Nissan XD does better than the F-150 5.0, so it's rating isn't that conservative.
01-18-2018, 11:33 AM
#42
Heat from the transmission is a killer if it cannot lock up the TC. When I ran my TT up I-70 to 11K feet in Colorado, it was with the trans TC unlocked and heat climbed quickly. Since it had 3.15 gears, it had to do it in 3rd gear @ 65 MPH, and it held it very well, but got hot in the process. I don't know if or when I plan to head west again with the current truck, but I would like to see how it does with 3.55 gears.
I could tell when the TC locked and unlocked as the trans temps would drop on flatter roads and start cooling, then I could hear the RPM's jump up and the temp start to rise again. This was in a 14 where you could set the center screen to the trans temps. It hit 230* that day.
I could tell when the TC locked and unlocked as the trans temps would drop on flatter roads and start cooling, then I could hear the RPM's jump up and the temp start to rise again. This was in a 14 where you could set the center screen to the trans temps. It hit 230* that day.
01-18-2018, 10:35 PM
#43
I have read that the 10-speed keeps the torque converter locked through all 10 gears. Even during shifts. It honestly doesn't feel like a traditional automatic at all. Once it's in gear it feels like an automated manual. it clutches and de-clutches during shifts and rev matches to hit the next gear just like a manual. You can really tell when manually downshifting it.
01-19-2018, 12:45 PM
#44
Grumpy Old Man
I lived in Denver for over 20 years, and crossed the Rockies numerous times dragging a 9k RV trailer.
When crossing the Rockies with a heavy trailer, I-70 thru Colorado is the worst possible route. Much better is I-80 thru Wyoming or I-40 through northern New Mexico. Best is I-10 through southern New Mexico, where you must pay close attention if you want to know when you cross the Continental Divide. When traveling west, if you absolutely must go through Denver, then consider a detour from Denver on I-25 to either I-80 or I-40.
On I-80 you cross the Continental Divide at South Pass = the Mormon trail. On I-40, the toughest climb is pulling up out of the Rio Grande valley, and you have to look twice to notice the Continental Divide.
01-19-2018, 01:59 PM
#45
I have read that the 10-speed keeps the torque converter locked through all 10 gears. Even during shifts. It honestly doesn't feel like a traditional automatic at all. Once it's in gear it feels like an automated manual. it clutches and de-clutches during shifts and rev matches to hit the next gear just like a manual. You can really tell when manually downshifting it.
I lived in Denver for over 20 years, and crossed the Rockies numerous times dragging a 9k RV trailer.
When crossing the Rockies with a heavy trailer, I-70 thru Colorado is the worst possible route. Much better is I-80 thru Wyoming or I-40 through northern New Mexico. Best is I-10 through southern New Mexico, where you must pay close attention if you want to know when you cross the Continental Divide. When traveling west, if you absolutely must go through Denver, then consider a detour from Denver on I-25 to either I-80 or I-40.
On I-80 you cross the Continental Divide at South Pass = the Mormon trail. On I-40, the toughest climb is pulling up out of the Rio Grande valley, and you have to look twice to notice the Continental Divide.
When crossing the Rockies with a heavy trailer, I-70 thru Colorado is the worst possible route. Much better is I-80 thru Wyoming or I-40 through northern New Mexico. Best is I-10 through southern New Mexico, where you must pay close attention if you want to know when you cross the Continental Divide. When traveling west, if you absolutely must go through Denver, then consider a detour from Denver on I-25 to either I-80 or I-40.
On I-80 you cross the Continental Divide at South Pass = the Mormon trail. On I-40, the toughest climb is pulling up out of the Rio Grande valley, and you have to look twice to notice the Continental Divide.
01-21-2018, 09:05 AM
#46
When looking at the differences between the HDPP and Max Tow ratings you need to consider that there is no industry standard for setting the GVWR of a vehicle as there is TWR. The purpose of the HDPP option is for increasing GVWR and Ford uses its own methods to set GVWR, as the same truck gets it TWR based on the SAE standard. How does the small increase in gvw weight and gearing effect engine cooling when towing? They seem to use the same radiator across the f150 models.
01-21-2018, 02:39 PM
#47
Magic HDPP engine coolant? 
01-21-2018, 04:56 PM
#48
Or is it the HDPP cool aid! 
Sorry I just had to poke fun at these HDPP fans... oh wait, I have one of those darn HDPP trucks 
I don't think there will be any noticeable difference in engine or trans cooling between an HDPP or Max Tow with the same transmission pulling the same hill at same speed with same load. 3.55 vs 3.73 gears isn't a big deal especially with a 10-speed. The extra weight of the HDPP can be offset by additional options that aren't available on the HDPP. In terms of the drive train and cooling, a Max tow and an HDPP are essentially the same. The reason to get the HDPP is for a little bit more frame rigidity (and it's only a little, 6.28 vs 5.73 section modulus), a little stronger rear axle (and again, only a little 4,800 rating vs 4.500 rating), stiffer rear springs (biggest physical difference, 4,800 rating vs 4050 rating for '18), stiffer front springs, but most importantly, that little tag on the door that keeps you legal with your family, stuff and a reasonable amount of tongue weight.
Sorry I just had to poke fun at these HDPP fans... oh wait, I have one of those darn HDPP trucks I don't think there will be any noticeable difference in engine or trans cooling between an HDPP or Max Tow with the same transmission pulling the same hill at same speed with same load. 3.55 vs 3.73 gears isn't a big deal especially with a 10-speed. The extra weight of the HDPP can be offset by additional options that aren't available on the HDPP. In terms of the drive train and cooling, a Max tow and an HDPP are essentially the same. The reason to get the HDPP is for a little bit more frame rigidity (and it's only a little, 6.28 vs 5.73 section modulus), a little stronger rear axle (and again, only a little 4,800 rating vs 4.500 rating), stiffer rear springs (biggest physical difference, 4,800 rating vs 4050 rating for '18), stiffer front springs, but most importantly, that little tag on the door that keeps you legal with your family, stuff and a reasonable amount of tongue weight.
Last edited by Gladehound; 01-21-2018 at 04:58 PM.
01-23-2018, 01:48 PM
#49
I agree it's not going up the hill in triple overdrive; most likely, it is in 2nd gear for the steepest part of the test. And I agree that we will never know the specific reason for the limit given. But,
What I was trying to explain:
All speeds are 35mph; the minimum required by J2807. Number are approximate for illustrative purposes, not down to 5th decimal place:
On Max tow truck: 2nd gear * 3.55 gears = 4,100 rpms = 335hp (more/less) . 335hp = 850k BTU/hr
On HDPP tow truck: 3rd gear * 3.73 gears = 3,100 rpms = 255hp (more/less) . 255hp = 650k BTU/hr
On HDPP tow truck: 3rd gear * 3.55 gears = 4,300 rpms = 355hp (more/less) . 355hp = 900k BTU/hr
Most like the HDPP can't hold 3rd gear/35mph with the maximum trailer, so it is shifting down to 2nd (same as MaxTow truck). Because of the higher rpms; it is able to make more power = 50k BTU/hr more. That 5% more heat might be straw that is breaking camel's back i.e. Can the radiator/inter-cooler/transmission cooler reject that much more load?
Turning more revs was historically good because the engine driven fan moved air at cubic of rpms i.e. +5% rpms moved +15% air. But the new electric fans are independent of engine rpm, so higher engine revs aren't necessarily useful.
Remember, J2807 is an SAE test to standardize ratings, not necessarily what is best in real life. Engineers are creative bunch when it comes to passing tests (see emissions testing). If higher axle ratio (numberically lower) produces better results, that's what they will publish the results of. So, I wouldn't put big money on that guarantee.
What I was trying to explain:
All speeds are 35mph; the minimum required by J2807. Number are approximate for illustrative purposes, not down to 5th decimal place:
On Max tow truck: 2nd gear * 3.55 gears = 4,100 rpms = 335hp (more/less) . 335hp = 850k BTU/hr
On HDPP tow truck: 3rd gear * 3.73 gears = 3,100 rpms = 255hp (more/less) . 255hp = 650k BTU/hr
On HDPP tow truck: 3rd gear * 3.55 gears = 4,300 rpms = 355hp (more/less) . 355hp = 900k BTU/hr
Most like the HDPP can't hold 3rd gear/35mph with the maximum trailer, so it is shifting down to 2nd (same as MaxTow truck). Because of the higher rpms; it is able to make more power = 50k BTU/hr more. That 5% more heat might be straw that is breaking camel's back i.e. Can the radiator/inter-cooler/transmission cooler reject that much more load?
Turning more revs was historically good because the engine driven fan moved air at cubic of rpms i.e. +5% rpms moved +15% air. But the new electric fans are independent of engine rpm, so higher engine revs aren't necessarily useful.
Remember, J2807 is an SAE test to standardize ratings, not necessarily what is best in real life. Engineers are creative bunch when it comes to passing tests (see emissions testing). If higher axle ratio (numberically lower) produces better results, that's what they will publish the results of. So, I wouldn't put big money on that guarantee.
Unless the truck is overheating and cutting power, even a 13,xxx lb trailer isnt gunna slow the ecoboost down much below 65 on the steepest climbs.
Last edited by mass-hole; 01-23-2018 at 01:55 PM.
01-23-2018, 10:25 PM
#50
I think you're right Mass-hole. Not only is the elevation higher, but the Ike is steeper than David Dam as well. The difference in steepness is more than the difference in weight. It would be a part throttle affair at the speed limit for the 3.5 EB regardless of rear and ratio.