OK here it goes!
When I buy a truck I am looking for power enough to do the job but not major overkill. So I am thinking 475-500 HP 18 speed trans. My biggest question is what is a good gear ratio for this combo? I want to be able to drive flat lands and mountains. In my head I'm thinking 3:55- 3:70. but I need some experts advice.
many thanks
Raider
Ratios
Discussion in 'Trucks [ Eighteen Wheelers ]' started by Raider, Feb 12, 2010.
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Roadranger ratio calculator http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf
each engine has a sweet spot .If you will ussually stay on road taller is better within reason and as you prolly know the 18 gives you the most usable range of ratios. I run a mech 3406 a 15 over with 3.70 and 11R24.5s, given the choice I would run an 18 and 3.55s, with a 3406E prolly 3.36 -
what brand engine and what size wheels/tires changes what ratio you'd need.
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I always bought my Petes with Cat's (475hp minimum), 18 speeds, and 3:55 ratios...I thought that combo worked pretty well, now keep in mind I got out of the O/O biz back in 2001 so things may have changed as technology has advanced and I have not kept up with all that..
I still read truckpaper once in a while and seems I see a lot of 18 speeds with 3:36 rears FWIW..
good luck !! -
3.70 is good horse power but moot point for a 18 speed. Stick with lower ratios.
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Many thanks for the Replies!!!
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I have a isx cummins 530 hp 18sp. with 3.91s and 11r 24.5s. I run up to 107,000 LBS on up to 12% grades and its perfect. At 80,000 OTR I would want 3.55s or 3.36s although 3.70 or 3.73s would be ok if you plan on running slow.
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