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Anyone with an 05, riddle me this....


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Just curious if anyone with either 3.42's or 4.10's wud post what their cruising rpm's are at the following speeds:

60 mph

70 mph

80 mph

 

I am looking for these values using stock tire size....i think they are 265/70/17.

 

Any info would be great

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...gain 1.5 mpg over 3.73s.I don't think you'd see that from 3.42 to 4.10.

 

 

 

It is coincidental. I'm getting about 1.5 MPG increase in city and highway with my '05 over my '03. Could be a combination of several things with the 3.42 being one reason.
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...gain 1.5 mpg over 3.73s.I don't think you'd see that from 3.42 to 4.10.

 

 

 

It is coincidental. I'm getting about 1.5 MPG increase in city and highway with my '05 over my '03. Could be a combination of several things with the 3.42 being one reason.

 

 

 

 

I believe that but I'd say losing the clutch fan and the charging system is contributing........it could be all the gear ratio but in the above post he said 3.42 to 3.73 and I'd think 1/2 to 3/4 mpg difference would be more realistic.

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I haven't verified the 4.10 numbers with observed readings off my tach, but on paper.....

 

With stock tires : LT24575R16E Tires on an 2005 2500HD

 

MPH RPM RPM RPM

RAR 3.73 4.10 Diff.

55 1,605 1,764 159

60 1,750 1,924 174

65 1,896 2,084 188

70 2,042 2,245 203

75 2,188 2,405 217

80 2,334 2,565 231

 

DEWFPO

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........I believe that but I'd say losing the clutch fan and the charging system is contributing........

 

 

Yeah, I forgot about the electric fan. I'd say with the gear ratio, fan, charging stuff, and maybe optimization of computer values, the MPG gained a bit. I also forgot the factory tires on this '05. They are rated as "mileage-efficient" according to an EPA chart. My 2003's are not listed on the chart.
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0.70 = Overdrive gearing

682.2 = Approx. wheel revs/mile on 245/75/16's

 

60MPH:

 

0.70*3.42*682.2 = 1633.18 revs/mile (RPM at 60 mph)

0.70*4.10*682.2 = 1957.91 revs/mile (RPM at 60 mph)

 

For another speed, just use a proportion, e.g. multiply by 7/6 to get RPM for 70 mph.

 

70MPH:

 

3.42: 1906.38

4.10: 2284.23

 

80MPH:

 

3.42: 2177.57

4.10: 2610.54

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awesome, thx guys

 

anyone else with any observed rmp readings in their 05?

 

 

 

On my 05 yukon xl with 5.3 and 3.42s rpm is about 2000. on my 2000 suburban with 4.11s rpm was about 2400 and 75 mph. I get am averaging about 2.5 mpg better with the 05 but if you drive with cruise on over hilly terrain, i would not recommend the 3.42s. mine sometimes shifts into 2nd gear at 75 mph and tachs close to 5000. I personally do not like the 3.42s. That my opinion.

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