I tow about 2000 miles a year here in the NE. My fiver scaled loaded is around the 11,800. I have no problems maintaining hwy speeds on hills. I would prefer diesel power but not worth the investment for my daily use. Get between 7-9 mpg depending on the headwinds.
2013 Keystone Sydney 340FBH 5th Wheel, 12,280 lbs wet
2015 GMC Denali 3500, SRW, Duramax, CC, SB
Take my posts for what they are, opinions based on my own experiences.
Marty, I have a spreadsheet to compare gearing. Here is a useful one comparing the GM 4-spd to the newer 6-spd. THe half ton ratios are similar, which is how GM can get away with 3.42 axle with the 5.3L and still have decent performance.
It would take an axle ratio over 6.0:1 with the 4-spd to get the first gear torque multiplication of the 6-spd with 3.73. Hmm, that actually lines up very closely with the first gear ratios of the 6-spd:
After 2 years with my 2003 F-150 with similar ratios to GM's HD 4-spd, I was hooked after some test pulls with newer 6-spds. Highway is little different, 5th gear is usable, somewhere between old 3rd and 4th gears, but accelerating on uphill onramps were killer when I only had 2 effective gears as 2nd could hit over 70mph. 5 usable gears vs. 3, 60% more power in first gear, all very noticeably better.
* This post was
edited 03/16/12 07:31am by APT *
A & A parents of DD 2005, DS1 2007, DS2 2009 2011 Suburban 2500 6.0L 3.73 pulling 2011 Heartland North Trail 28BRS 2012 VW Passat TDI
I'm sure that is the case. Same for when I bought my navistar, got similar sheets showing the differences between a 4 sp auto, 5, 6 and 7 sp manuals. All had 4.33 gears, all were direct drive, but the allison auto only had IIRC about a 5-1 first gear including TC, where as the 7 sp was 10.08. the gear shift were as wide as 1400 rpms to as little as 700 for the 7 sp. Needless to say, I went with the 7 sp when I bought my truck. One could see that more gears, closer together would allow better speeds when one could not pull/use the gear above.
A lot of folks also were doing the same with the NV5600 behind the cummins when it first came out, but first, direct and od were the same, but gear below direct went from a 1.7 to a 1.3 which allowed a bit more speed when one could not hold direc but could go to redline.
At the end of the day, it is not always about the axel gear, the trans gear IMHO can mean more to how well one performs than a given axel. IE making sure the spits line up with speed one drives etc. Hence also why, I do not believe in the BS engine/axle ratio gcwr. Nor do I believe the new SAE specs will be the savior for how well a rig will tow or not. As it does not say how steep a grade one can pull in first gear. Only 4 start in 5 min on a 12% grade. I see those daily in my area. I do not get worried or take notice until 20%, and 30% is minimum I want a rig to go up once mind you at what I am going to be weighing in at. My navistar while all the trannies were rated to 35K lbs gcwr, the Auto would only go up a 20% grade, the spice 7 was the steepest at 35%, that is with a measly 175/335 non turbo 7.3 v8. My dmax will only do 25% at 20K lbs! Which is the better tow rig?
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer
You are probably correct, in that a 10K limit could be low, then again, at the end of the day, it also depends upon the end user, hills they go up etc. as to "IF" that rating is correct. If on needs to pull 40% grade, ie about a 20degree hill, then 10K may be all it could do before literally stalling out. From specing and seeing how mdt/hdt rigs are speced, until the sae specs also include a steepest grade, and different specs for the frontal area sq ft, aerodynmics etc
While I agree with the spreadsheet, folks need to be careful. My Dad has an 08 Chevy 2500HD with the 6.0/6sp 4wd ECSB 3.73 and I have the 2011 GMC 2500HD 6.0/6sp CCSB 4wd 3.73 gears. My tires (not just the wheels), but the actual tires are 2" taller (diameter) than his. Using the spreadsheet above and including the tire diameter, a comparison can be made.
well i have a 2004hd2500 410gears with a 6.0 and Im up grading to a 3500 diesel I was told that my truck would pull my camper with no problem but only on level ground and interstate it does great but only gets 6-7 mpg but on mountins it strugles bad my camper is a 39ft sandpiper with a dry weight of 10550 loaded alot more lol still up inthe air either a ford or chevy the Fords look so good but im loking in the range of 2004-2008 price is the issue and I hear that the 6.0 fords have alot of issues and so did the 6.6 duramaxso i will just keep looking good luck with your truck and God bless!!
You final ratio would be about 1 gear taller than you dad, ie, you 3.73 is really about a 3.42 vs the 3.73 he has when it come to how fast the motor is going etc. Assuming you are truly 2" in diam more than him. A 245 -16 or the 17 series is about 30.5", a 265's are usually 31.5" or 685 revs per mile for the 245 tires, and 655 for the 265 rubber tires.
If the above usual differences I have seen are true, then you final ratio is equal to about a 3.55 to 3.6.
I do agree, one has to look at the tire diam vs axle ratio vs trans gears etc to really see how good or bad you are geared.