75 mph@2000RPM
#22
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My Z28 had 2.73 and went to 3.73. I would average within 2 MPG's of having the 2.73's. going on a few 300+ round trips the car got about 23 MPG's on the highway doing around 70 mph.
#23
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^^^ thanks for the 3.73 23mpg post.
5 posts back I estimated that 3.73s' would have been spec'd at 24mpg had they built them.
There isn't much mpg variance among all the possible ratios from 2.73, 3.23, 3.42, 3.73. 4.10, 4.56 ( I know I omitted 3.08, 3.90, 4.30). The computer controlled air/fuel ratio does a good job handling it, much better than if you just calculated mpg change based on mechanical ratio change.
As ratio changes to a higher numerical ratio, the powertrain then has a better mechanical advantage over the vehicle weight and wind resistance. A better mechanical advantage equates to less power required which in turn the computer can start demanding less fuel while still maintaining the OEM range of acceptable A/F ratios.
5 posts back I estimated that 3.73s' would have been spec'd at 24mpg had they built them.
There isn't much mpg variance among all the possible ratios from 2.73, 3.23, 3.42, 3.73. 4.10, 4.56 ( I know I omitted 3.08, 3.90, 4.30). The computer controlled air/fuel ratio does a good job handling it, much better than if you just calculated mpg change based on mechanical ratio change.
As ratio changes to a higher numerical ratio, the powertrain then has a better mechanical advantage over the vehicle weight and wind resistance. A better mechanical advantage equates to less power required which in turn the computer can start demanding less fuel while still maintaining the OEM range of acceptable A/F ratios.
#24
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My only concern is with the 10 bolt. The greater the mechanical advantage the rear has the less tooth contact (# of overlap) and size the pinion gear seems to have with the ring gear. Maybe I'm fearful of nothing?
#25
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One correction of one of my post. The 23 mpg average was for the entire trip with the highway portion being about 50% averaging about 70 mph. Of course there was in town driving which I am unsure if mileage really suffers as it takes less effort to get moving. Be that as it may, I did have some fun driving on the trip with some spirited driving. lol So I'm thinking the MPG's would be better without that aspect.
#26
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Per both of them, the smaller pinion (like a 4.10) is not any weaker than a 3.42. Per them. when we change ratio for performance we have a tendency to abuse them more.
I've been running 4.56s' for 14 years now, a used Richmond set I picked up at the Canfield swap meet for $25. I set the pattern up for maximum contact irregardless of noise, It's difficult to set up a used set anyway. The 4.56s' have the smallest pinion gear size. 14 years now with dragstrip runs and much abuse in 'street fun', they're fine.
#27
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Good post. I've been to that Summit.
Agreed that only one tooth can be fully seated but with multiple others partially I would think, I'm probably wrong, it would be stronger.
I've used both Motive and Richmond with no issues in automatic and stick cars.
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I've used both Motive and Richmond with no issues in automatic and stick cars.
#29