redneck wrencher

My question is, "In what transmission gear range was the maximum trailer tow capacity computed with the gear ratio of the drive axle listed on the towing chart?" We have a 6 speed transmission. Locking out upper gear ranges will change your final drive ratio, increase rpm/torque, and provide better "leverage" to do work. It's about finding a balance and a "sweet spot'' in the engine rpm for better low end torque and not lugging down the engine. This is affected by engine design, axle ratio, transmission gear range, tire size, and must work harmoniously together. With my 5.0 and 3.55 axle ratio, I have found that 4th gear provides the best power for towing my travel trailer, while only sacrificing about a few tenths mpg from running it in 5th. I do run 5th on "flat ground" without issue. These transmissions have the capacity to run in any gear (2nd-6th) all day long; rpm being the limiting factor. Why not simply drop a gear, instead making the truck work any harder than it has to?

Don_Parsons

I hear yha redneck as lugged down to low could be as bad *** reving to high,,, the sweet spot is what I'm after. Geared more as a car since 98% of my driving will be running empty. Drop some gears when needed when packing the 600 lb ATV.

The 3 other units I have work well for different applications at the farm.
Unit 1 for pulling goose-neck dually tri-axle trailer at 30.000 lbs with Dodge 550 cummings @ 456 gearing.
Unit 2 that pulls 33 foot holiday trailer with quads at 20.000 lbs Chev 8.1 L @410 gearing.
Now unit 3 that will pull nothing to maximize fuel mileage.

Once I know how the motor powers up the truck the way it comes, it will give me an idea of what I need to do for gearing and tire size.

The plan is test drive it the way it is for 10 to 15.000 kms in head wind, rain, up and down hills, and with the intended pay-load "600 lb ATV, if the motor is spinning freely with no effort, then I'll do the larger tire size and re-test again.

If motor still spins free with second test, then I'll address gear-set at that point,,, yes as you mentioned. Don't put motor and tranny into lug mode as it will not improve fuel mileage.
I like what you said about dropping a gear if I choose the taller gears when running with ATV in the box,,, 4th or 5th in tranny to prevent lugging, I can use 6th with no pay-load when using it as a car.

My BC pal did this with his 1980 GMC as he ran with over drive mode off when packing junk, then used OD when sifting down the hwy fast. Ha.

Can't wait to get the unit home to see how this 3.7 L motor works. It's been 36 years since I've own a 6 banger.

I will defiantly chime in with feed back as I get things under way. I know that many good folk on this forum can help me out when needed.

From pal Don in Western Canada.

atwowheelguy

J2807 test procedures
http://www.automotive-fleet.com/fc_r.../pdf/j2807.pdf

redneck wrencher

This excerpt from the pdf does not give specifics. Being an automatic, downshifting may occur during acceleration, unless in Manual Mode as the case of the Selectshift option. Transmission gear range is not an absolute.


4.3.5.4 Procedure for Automatic Transmission-Equipped Vehicles


Select highest available forward gear position unless otherwise specified by tow-vehicle manufacturer. As the


combination begins ascent, accelerate as required to a speed between the minimum speed requirement specified in the


Table 3 Performance Attribute of Highway Gradeability for the tow-vehicle under test and the posted 45 mph speed limit.


When posted speed limit changes to 55 mph and again to 65 mph, it is the tow-vehicle tester’s choice to run at any speed


between the minimum speed requirement and the posted speed limit. The minimum speed requirement applies from the


Davis Dam turnoff (County Road 68), 1.3 km (0.8 miles) after the start of the test grade as shown in 4.3.5.2 to the end of


test run. Note the change to 55 mph posted speed limit occurs 1.4 km (0.9 miles) after the start of the test grade and the


65 mph posted speed limit occurs 3.7 km (2.3 miles) after the start of the test grade.

atwowheelguy

It only has to maintain 40 mph up the grade without overheating or breaking something to pass the test.

Don_Parsons

That's to hard to figure out as its easier for me to hook onto a 5000 lb trailer and run the hill from bottom to top.

Start at bottom of hill at 0 kpr, then rug the floor board till it maxes out at 100 kpr/ 62 mpr, record the time it takes to get up to speed.

If the unit struggles to maintain getting up to speed/ or holding its own, then one might want to address motor performance, tire size, or gear ratio "if" one chooses this 100 kpr rating.

This is why I own many trucks since I can pick the unit for each task. A good option for those that can't is to pick a unit that is 20% more of what they need, just an option if one chooses to go this route.

Simple, easy fast. Just a thought is all.

Pal Don

Edited: PS: One can't go wrong picking the Dodge V10 Ford 6.8 or Chev 8.1 in gas motors, diesel trucks from all the builders work good to.

Don_Parsons

I just raped up a 1 year trip across all of Canada and 36 USA States, I did not use this truck since it gets 4 or 7 mpg, Ha. 8.1 L gas with Allison auto and 4.56 gearing.



I chose the bit lesser on power to gain a smaller fraction of gas range. 11 to 12 mpg
5.7 L auto with 373


Was packing 2 light weight dual sport bikes in the truck box with 3500 lb fully loaded 19 foot holiday trailer. Old truck would pull all day long at 72 mpr/ 116 kpr as I covered 38.000 kms/ 23.600 miles on that 1 year outing.

I wish now that it had 410 gearing as the tranny took on a bit of wear & tear. Re-con tranny is cheap fix if needed later on.

Like redneck mentioned, drop a gear in the tranny and get the revs up to make lots of oil pressure, fluids circulate better at 3700 to 4000 grand, Ha.

The 8.1 L works very well between 2800 and 3200 rpm as it puts out a swack of foot pounds. Like the sticker says on drive shaft, "Caution,,, do not touch when in motion."

Pal Canada Don

Edited:
Plan is to beet that mileage on next North American trip with used 2012 ford with no holiday trailer,,, back seat will become living quarters on that trip.

Pack light, 1 light weight atv, 1000 watt gen-set, 2 small tool boxes, live on the road, a few parts & supplies if needed, 2 five gallon gas cans to pass rip off gas stations, large cooler for day lunches since there ain't no restraint stops, and coffee cup, Ha.