RV.Net Open Roads Forum: Search

RV Blog

  |  

RV Sales

  |  

Campgrounds

  |  

RV Parks

  |  

RV Club

  |  

RV Buyers Guide

  |  

Roadside Assistance

  |  

Extended Service Plan

  |  

RV Travel Assistance

  |  

RV Credit Card

  |  

RV Loans

Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  



Open Roads Forum  >  Search the Forums

 > Your search for posts made by '4x4ord' found 641 matches.

Sort by:    Search within results:
Page of 33  
Next
  Subject Author Date Posted Forum
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

3.31 and 3.55 are both good ratios for towing anything a SRW is capable of towing. Maybe a good way to compare the two is like this: With the 3.31 ratio the truck will spend a little more time in each gear than a 3.55. (The travel speed range of each gear is about 7% more for each gear with a 3.31 final drive) This means there is apt to be times when it is desirable to lock out 10th gear with the 3.31 gears (maybe towing into a stiff wind). When operated as a 9 speed the 3.31 will do less shifting than the 3.55 equipped truck. When towing light or running empty the 3.31 gears will provide better fuel economy. I think even if I was planning on 90% of my truck’s use to be towing a heavy RV I’d have ordered 3.31 gears and be prepared to lock out 10th gear under certain conditions.
4x4ord 01/25/21 08:33am Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

Yes, I know the owner’s manual says to not use cruise when towing. I end up shutting cruise off going downhill letting it coast up a few mph. realy? my manual says to use cruise control as that the only way the enging braking decending hills works. I think you need to read the manual again. Steve The Ford exhaust brake started out from 2011 to 2014 as poor. However, with enough engine rpm the 6.7 would hold back a decent size RV. It really doesn't matter whether you've set the cruise or not, what mattered was that the transmission was in a low enough gear to get the engine rpm up high enough to hold back the load. If you find yourself braking too much you need to slow down enough to get the transmission to drop another gear. 2015 and 2016 6.7's have a different turbo that provides much better exhaust braking but the principle is the same .... if the engine can't hold you back in 4th or 3rd you need to slow down enough to get the transmission to drop to 3rd or 2nd. The Ford exhaust brake has not changed from 2017 until present. It still relies on high engine rpm to provide effective braking. The 2017+ system has a full on and an auto setting. The auto setting attempts to build only enough back pressure to hold the truck at the speed it was travelling at when the accelerator or brake pedal was last released. If the engine rpm reaches redline the wheel and trailer brakes come on periodically to slow the truck down a few mph before releasing again. The computer monitors the amount of automatic wheel braking being performed and determines an approximate temperature of the brakes. If the the brakes get hot it will stop automatic braking and warn the driver of the condition. When the cruise control is used on the Ford trucks with adaptive cruise control the wheel brakes are automatically applied and work in conjunction with automatic downshifting of the transmission and exhaust braking.
4x4ord 01/24/21 08:34pm Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

^^^^At 25000 lbs and on 7% grade a 475 hp truck will pull down to about 58 mph. The difference in 3.31 gears vs 3.55 gears is this: If the truck with 3.55 gears and 34” tires will be running at 2600 rpm in 6th gear it can put out 475 hp. The truck with 3.31 gears and 34” tires will be running at 2800 rpm in 5th gear at about 56.4 mph and it will be putting out about 462 hp. But if the hill gets a little steeper the 3.31 ratio equipped truck gains hp as it slows down where as the 3.55 equipped truck will loose power as it slows. So really both gear ratios will perform extremely well with loads under about 18000 lbs. once you get into dually territory 3.31s are no longer as desirable nor are they available. Are you basing your logic on towing a 25K loaded RV? Not many if any are towing a 25K RV. But maybe you are referring to a 25K GCWR which is a realistic figure. But if 34" tires are required to prove your point, you are stil not providing real life scenarios. So far I'll stick by my comments that the 3.55 will deliver a better towing experience simply because it will hold gears a little more while going up the grade and be less likely to downshift. 3.55 may also get you started a little easier. But if your towing with 34" tires for some reason::? 3.31 maybe better:@ Yes my math is based on 34" tires and 25k lbs combined weight. With a ten speed if you find yourself towing in a situation where the transmission is constantly shifting in and out of 10th you can simply lock out tenth gear ... or even nine and tenth if needed.
4x4ord 01/24/21 11:41am Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

Personally, I'd want a 3.73 axle for towing. The torque amplification is more easily handles in the axle than the transmission. Sure you have multiple gears and you can drop down to 4th or even 3rd gear to pull the grade. Ken When your cruising down the highway at 62 mph with a typical rv the torque output of the engine might be about 500 lbft in 10th gear with 3.55 gears vs 536 lbft with 3.31 gears. When you hit a hill and the rear wheel torque demand increases the 3.31 truck will drop to 9th, 8th or 7th before the 3.55. This is desirable. There is no point in putting high power (1000 lbft of torque) through the overdrive gears to speed the driveshaft up just to run that power through a high ratio rear end to slow it down again.
4x4ord 01/24/21 11:36am Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

^^^^At 25000 lbs and on 7% grade a 475 hp truck will pull down to about 58 mph. The difference in 3.31 gears vs 3.55 gears is this: If the truck with 3.55 gears and 34” tires will be running at 2600 rpm in 6th gear it can put out 475 hp. The truck with 3.31 gears and 34” tires will be running at 2800 rpm in 5th gear at about 56.4 mph and it will be putting out about 462 hp. But if the hill gets a little steeper the 3.31 ratio equipped truck gains hp as it slows down where as the 3.55 equipped truck will loose power as it slows. So really both gear ratios will perform extremely well with loads under about 18000 lbs. once you get into dually territory 3.31s are no longer as desirable nor are they available.
4x4ord 01/23/21 08:46pm Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

My thought is that while in tow haul mode..it won't downshift excessively ... and provide better fuel mileage... most of my miles are not loaded... But you make a good point if you buy it to tow...then get something to tow with... if a person wanted to save money.. don't buy a camper to begin with..lol. So far most of the people have been happy with the 3.31 Ok the idea is better MPG's. Maybe if I never towed 3.31 would be preferred. However given a choice for someone who TOWS 3.55 will always provide more towing performance. MPG difference between 3.31 and 3.55 can't be much?:@ I guess you could make the same argument that towing performance improvement between 3.55 vs. 3.31 can't be much!....;) Either way I'll go with towing performance. A diesel pick up will never deliver great MPG's. However I want all the performance I can get when pulling a long steep grade. How will 3.55 gears perform better than 3.31 gears on a 7% grade towing a 17k fiver? (A 7% grade should be steep enough to slow the Powerstroke down to about 58 mph towing at 25000 lbs combined weight.)
4x4ord 01/23/21 06:36pm Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

^^^^ With the 10 speed 3.31 gears are available with 20’ wheels in the SRW Ford trucks. Dropping gears on hills is no big deal. In fact it makes sense to be in direct (4th gear with the 6 speed or 7th with the ten speed) when you’re pulling grades. The additional torque of the newer engines coupled with the lower 1st gear ratio of the 10 speed transmissions make 3.31 gears an excellent choice for lighter trailers. ( by lighter I mean under 20,000 lbs). Once you go dually with the Ford, 3.55 becomes the highest ratio offered.
4x4ord 01/22/21 03:03pm Fifth-Wheels
RE: Ford super duty 3.31 rear end. Will it be a big mistake. ?

I've got a 2017 F350 with 3.55 gears and 20" wheels that I tow a 16k lb rv with. My 2021 will be 3.31 gears. The 10 speed has a pretty low ratio reverse which is going to be a downer even with 3.31 gears.
4x4ord 01/21/21 08:47pm Fifth-Wheels
RE: Build my TV

I've got a new Ford on order and in the mean time I've taken a Ram for a test drive (which is actually quite a bit as I've not set foot in a Ford dealership). At the same price I'd go Ford but if Ram would beat Ford by a dollar I might be willing to give Ram a try. As it is the best I can do on a Ram Limited is a couple thousand more than what a Ford Platinum comes in at. For a trailer with a GVWR of 17k you could go SRW or dually .... either would do the job. I'd opt for a SRW short box.
4x4ord 01/21/21 08:38pm Tow Vehicles
RE: 2022 Ford Super Duty interior?

Why not buy a new 2021 Super Duty and then replace it when the 2023's come out?
4x4ord 01/21/21 08:19pm Tow Vehicles
RE: Newer 5ers, Slider Hitch Required For Short Beds?

I have no need or desire for a sliding hitch but if I was to get one it would be an auto slide. If I had to manually slide my hitch I would never slide it. My father has taken out the back window of his Dodge twice in the 16 years that he has owned his truck and he has a manual slider ... that he doesn't use.
4x4ord 01/18/21 12:42pm Fifth-Wheels
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Here's a fun question, what if we "sand-bagged" the PSD with an Aisin 6 speed? The be fair, I used a 4.10 rear end vs the 3.31 on the 10 speed. Surprise the overall 1st gear ratio becomes nearly identical, so performance is strictly down to gear gap: https://i.imgur.com/0KRgbVJ.jpg The thrust tells us something really interesting: https://i.imgur.com/aTtnKO6.jpg The Aisin is only able to hit 3rd gear, but the final thrust (and therefore overall gear ratio) is almost an exact match to 4th on the 10 speed. This means given enough time (big enough hill), the Aisin truck will reach the same speed. Sure enough, my raw data says @ 200 seconds, the Aisin truck hits 44.7 mph, @ 2752 rpm and 475 hp. That's 1 mph faster. At 190 seconds into the race, the 10 speed has covered 3493 meters, and the Aisin 3494. So the Aisin passed the 10 spd by 3 feet at 3 min 10 sec. It was quite a bit behind at the start. Comparing the acceleration or even hill climbing traits of a 3.31 10 speed to that of a 4.10 6 speed really needs to be shown in light of comparing the fuel economy in high gear between the two set ups. In order to obtain similar cruising fuel economy the two transmissions would have to be set up with similar final drive ratios .... with final drives equal the advantage of the 10 speed would be revealed comparing acceleration and heavy pulling performance.
4x4ord 01/14/21 11:58am Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Here's a fun question, what if we "sand-bagged" the PSD with an Aisin 6 speed? The be fair, I used a 4.10 rear end vs the 3.31 on the 10 speed. Surprise the overall 1st gear ratio becomes nearly identical, so performance is strictly down to gear gap: https://i.imgur.com/0KRgbVJ.jpg The thrust tells us something really interesting: https://i.imgur.com/aTtnKO6.jpg The Aisin is only able to hit 3rd gear, but the final thrust (and therefore overall gear ratio) is almost an exact match to 4th on the 10 speed. This means given enough time (big enough hill), the Aisin truck will reach the same speed. Sure enough, my raw data says @ 200 seconds, the Aisin truck hits 44.7 mph, @ 2752 rpm and 475 hp. That's 1 mph faster. At 190 seconds into the race, the 10 speed has covered 3493 meters, and the Aisin 3494. So the Aisin passed the 10 spd by 3 feet at 3 min 10 sec. It was quite a bit behind at the start. Comparing the acceleration or even hill climbing traits of a 3.31 10 speed to that of a 4.10 6 speed really needs to be shown in light of comparing the fuel economy in high gear between the two set ups. In order to obtain similar cruising fuel economy the two transmissions would have to be set up with similar final drive ratios .... with final drives equal the advantage of the 10 speed would be revealed comparing acceleration and heavy pulling performance.
4x4ord 01/14/21 11:54am Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

" 6 spd vs 10 spd would make very little difference in flat out performance." I have said this for a LONG time. You also sang the praises of the 68RFE. Until you moved to the Aisin..... More gears makes little difference to a 420 hp 1075 lbft engine. My guess is Ram will go to a transmission with more gears and boost the peak Hp to make use of those gears.
4x4ord 01/13/21 03:47pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

^^^ I figure a Ram towing a typical 20,000 lb toy hauler should get around 9 mpg at 62 mph. If you use the BSFC map that we have and figure the Cummins will be running in the 205 g/kwhr area of the bsfc map we can come up with the kw required to tow a 20k trailer at 62 mph. 9 miles per gallon is 22182 grams of fuel per hour. 22182/205 = 108 kw or 145 HP. From there you should be able to come up with what you think are reasonable numbers for surface area, rolling resistance and coefficient of drag. (Keep in mind that the calculated power requirement is at the crankshaft so rear wheel hp would only be about 123 to 125 hp.)
4x4ord 01/13/21 01:50am Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Here are some rpm points along that torque curve with the corresponding torque outputs: https://i.imgur.com/TiWg5YCl.png
4x4ord 01/12/21 08:38pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Good grief... Yup, lot's of confusion. I'm not sure what happened. Immediately after posting my torque curve reflecting 430 peak HP I checked Ram's website and saw they are advertising 420 HP, so, I changed my torque graph within about an hour. I don't know if Roy got a copy of my graph before I changed it or if he was thinking 430 HP from other sources. You can find claims anywhere from 400 to 430 HP for the 2021 Cummins. Edit: I'm almost certain that even Ram's website was initially showing 430 HP for the HO engine but they currently are advertising 420 HP. Let's me try re-shaping the equation for 420 hp. I too was confused, some sites quoted 430 hp, some 420. I don't believe the official specs are on Ram's site yet, but I do see 420 stated on Cummins' site: https://www.cummins.com/news/releases/2020/12/04/2021-ram-heavy-duty-legendary-pickup-engine-better-ever What we really need is the official tq / hp curve. If the curve has flat hp plateau like we see on the marine QSB, then a 6 spd vs 10 spd would make very little difference in flat out performance. In fact, tonight I'll try it for fun with the QSB curve. Let's call it a lightly modded / chipped truck - i.e. programmer in "tow" setting. I bet it'll make absolutely 0 difference (engine hovers @ constant hp during an upshift) The Ram site is showing 420 peak HP but doesn't say rpm and the peak torque of 1075 and again doesn't mention the rpm. I would be willing to bet the torque curve I drew is very close to what the actual torque curve will be. If you want a torque curve that would produce a perfectly flat power curve, it would look like this: https://i.imgur.com/WJH7ejjl.png Such a torque curve would generate a power curve like this: https://i.imgur.com/MH9s56Ql.png
4x4ord 01/12/21 08:31pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

The fuel economy advantage the 10 speed has over the 6 speed is negligible .... many of the scenarios we considered there was no advantage and when there was it was at the very most 4-5% in a very specific case. If I was getting a Ram I certainly wouldn't be waiting for a 10 speed. Here is a chart that shows the advantage a 10 speed behind the Cummins would give over leaving it as a 6 speed: https://i.imgur.com/KeXh66Vl.png
4x4ord 01/11/21 06:20am Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Good grief... Yup, lot's of confusion. I'm not sure what happened. Immediately after posting my torque curve reflecting 430 peak HP I checked Ram's website and saw they are advertising 420 HP, so, I changed my torque graph within about an hour. I don't know if Roy got a copy of my graph before I changed it or if he was thinking 430 HP from other sources. You can find claims anywhere from 400 to 430 HP for the 2021 Cummins. Edit: I'm almost certain that even Ram's website was initially showing 430 HP for the HO engine but they currently are advertising 420 HP.
4x4ord 01/10/21 11:34am Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Roy, now that you’ve made your spread sheets is it a fairly simple matter to change the polynomial to get the values to reflect a peak HP of 420 instead of 430? ... I might have initially posted a wrong torque curve before I recognized my mistake and changed it. Because the peak HP is 420 instead of 430 the 10 speed advantage will be considerably less.
4x4ord 01/09/21 09:24am Tow Vehicles
Sort by:    Search within results:
Page of 33  
Next


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2021 CWI, Inc. © 2021 Good Sam Enterprises, LLC. All Rights Reserved.