3.42 ?
06-04-2010, 01:54 PM
#16
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06-04-2010, 03:45 PM
#17
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3.42's will put about 8.3% less tq to the wheels for any given rpm.. If you think you need that extra tq then go 3.73's, if not the 3.42's will most likely yield the best economy.
06-05-2010, 07:26 AM
#18
Administrator / Severe Concussion Aficionado
But is sure looks good.
35's are plenty big enough for me.
Thanks for all the info. Good thread here.
06-05-2010, 07:57 PM
#19
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mileage
i average between 17-22 mpg. depending on speed, wind, terrain.
loaded (9-11k lbs) 9.5-12.
in town,
mid teens, depending on right foot...
single rears, 3.73's and stock tires
06-09-2010, 09:09 AM
#20
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My 2010 with 3.42's, stock 265/70R17 tires, and Auto is getting about 16-17mpg combined city/highway mileage.
2010 3500 CC LB 4x4...I'm happy with the mileage, but better yet would be nice!
Chris
On my old 98 I ran 3.54's, Auto and 36.3" tall, 145lb each 285/70R19.5's, and the 6.7L drive WAY nicer than that ever did, even with 150hp less!
2010 3500 CC LB 4x4...I'm happy with the mileage, but better yet would be nice!
Chris
On my old 98 I ran 3.54's, Auto and 36.3" tall, 145lb each 285/70R19.5's, and the 6.7L drive WAY nicer than that ever did, even with 150hp less!
06-09-2010, 10:15 AM
#21
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Confused?
I am confused by this (trying to understand not saying this is not true). My logic was that I could have the economy and all the torque I needed via gear selection. Although I probably will never tow/haul a heavy load. It seems to me that by locking my 3.42 truck in 5th gear I will have more torque at any RPM than a 3.73 truck in 6th gear. Therefore, as long as there are enough gears and a way to select them, the 3.42 gears gives me higher ratio options without losing torque I may need. I realize I lose the equivalent of a "gear" on the low end which I don't seem to need. I do like my range of options with the 3.42 and the 6 sp auto (but as I said I am not towing 20K lbs). I seem to be averaging 16 to 17 with only 1500 miles -- considering the weight, wind resistance and emissions junk it doesn't seem bad to me. Ed
06-09-2010, 10:30 AM
#22
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I am confused by this (trying to understand not saying this is not true). My logic was that I could have the economy and all the torque I needed via gear selection. Although I probably will never tow/haul a heavy load. It seems to me that by locking my 3.42 truck in 5th gear I will have more torque at any RPM than a 3.73 truck in 6th gear. Therefore, as long as there are enough gears and a way to select them, the 3.42 gears gives me higher ratio options without losing torque I may need. I realize I lose the equivalent of a "gear" on the low end which I don't seem to need. I do like my range of options with the 3.42 and the 6 sp auto (but as I said I am not towing 20K lbs). I seem to be averaging 16 to 17 with only 1500 miles -- considering the weight, wind resistance and emissions junk it doesn't seem bad to me. Ed
So with some basic numbers (Cummins claims at least 555 ft/lbs from 1400-2900 on the 5.9, the 6.7 will be at least the same)
Since the tq curve is very flat on our engines you can calculate that as
1898 ft/lbs to the wheels in 5th and 3.42's
1404 ft/lbs to the wheels in 6th and 3.42's
2070 ft/lbs to the wheels in 5th and 3.73's
1531 ft/lbs to the wheels in 6th and 3.73's
Obviously more engine tq is more to the wheels, but these should be min WOT numbers.. Also even thou the tq curve is very flat, hp still make a big difference.
65mph in 5th is very doable for both 3.42's and 3.73's (2450 vs 2650).. But 65 in 6th is easier with 3.73's (1800 vs 1975)..
On a side note, with my TT I have to be above 2000 rpms (Closer to 2100-2200) to be able to pull most hills in 6th.. thats 75-78 mph.. thats just too fast to tow, with 3.42's it would be even faster 83-85, and thats not smart or legal.... So the drop to 5th happens on any large hill, 3.42's would be nice for the rpm drop here.. but the tq with 3.73's is also nice... Its a trade off for sure.
06-09-2010, 08:55 PM
#23
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If you plan to pull, I'd go with the 3.73's. If you're mostly running light, the 3.42's would be fine I believe. I have a 2010 G56 with 3.73's and have upgraded to 285 tires (~3% rpm drop) and I don't mind it at 70-75. You get used to is and I'm sure it's not hurting anything... According to Cummins, the 6.7 peak efficiency and power comes >2100 RPM. I find my 6.7 sort of sluggish under 2k on hills, even empty, so I don't mind it.
-truckin-on
-truckin-on
06-10-2010, 02:00 PM
#24
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Pulled the 48' enclosed race trailer this weekend...about 25K GCVW. Pulled hills in 5th like a dream at 72mph, cruise set. If I wanted to, I could drop to 6th on the flats and still pull most hills at 70mph, cruise set at 72mph.
I was amazed how well the engine likes 1600RPM loaded like that...I didn't think I would be able to run 6th at all, but it will. Now, how well the tranny likes pulling like that in 6th, at 1600RPM, I don't know. I'll bet it hates it.
2010 3500 SRW CCLB...68RFE and 3.42's
Chris
I was amazed how well the engine likes 1600RPM loaded like that...I didn't think I would be able to run 6th at all, but it will. Now, how well the tranny likes pulling like that in 6th, at 1600RPM, I don't know. I'll bet it hates it.
2010 3500 SRW CCLB...68RFE and 3.42's
Chris
06-12-2010, 02:44 PM
#27
Administrator / Severe Concussion Aficionado
Just left the dealer in Marshall Tx. Water pump on the mega crapped out. While there was looking at the new 3500 duallys. They had one with a g56. Took it for a drive.... Im in love. Man it was so nice. Im gonna have one before its over with.
Anyway, judging from the way it ran I figured it would have the 3.42's
Nope sticker said 3.73's. The powerband seemed just about right and I think with taller tires I would want to have the 3.73's.
Anyway, judging from the way it ran I figured it would have the 3.42's
Nope sticker said 3.73's. The powerband seemed just about right and I think with taller tires I would want to have the 3.73's.
06-12-2010, 04:30 PM
#28
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But the newer G56 has the .74 final drive ratio so that might not be as bad with the 3.73....
Yep -- The 2010's are amazing.
06-12-2010, 04:43 PM
#29
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Interesting. After living with a first generation G56 with the .79 final drive ratio and a 3.73 I'm SCARRED FOR LIFE and just assume nothing but a 3.42 would do.
But the newer G56 has the .74 final drive ratio so that might not be as bad with the 3.73....
Yep -- The 2010's are amazing.
But the newer G56 has the .74 final drive ratio so that might not be as bad with the 3.73....
Yep -- The 2010's are amazing.
06-12-2010, 05:42 PM
#30
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Just this past week I used the cruise in my Cummins Diesel MH for the first time up grades - for years I would turn it off in the mountains and drive it myself - and I noticed I was running a little cooler and seemed to do a little better up the grades. Makes me wonder if the cruise has a better ability than I do to keep the engine where it gets optimal torque. Think I'll start using the Ram's cruise more, and see how it does in the mountains. Between Chris' comments and my MH experience, I'll bet it goes better.
