mileage
Thread Starter
1st Gear
Joined: Jan 2013
Posts: 1
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mileage
I have a 1989 vett and change the rear end to 3 73 it works well but almost have no first gear. Don t know what kind of mileage I am getting but it is not good, used to get 26 mi on freeway. I have been told that it would cost 500.00 to fix speed omp. On freeway at 70 I am running about 24oo rpm. I was just wonding would 3 07 rear end, that kind of mileage that I used to get. I think I had 2 59 rear end. Thanks. Nobby Pann
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Is your TV cable adjusted correctly?
Did you put the 373 in for acceration? Mileage will go down some but not a whole lot sure youre still over 20 hwy which isnt bad for a V8 they got 24 stock
Sure beats those 2.73s
Did you put the 373 in for acceration? Mileage will go down some but not a whole lot sure youre still over 20 hwy which isnt bad for a V8 they got 24 stock
Sure beats those 2.73s
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
Gear ratios are a trade off.
The higher numerical gears will help it accelerate better, but at the expense of fuel mileage at cruise.
The higher the rpm at your cruise speed the worse your mileage. So a 2.59 will have lower rpm and better mileage than a 3.07, and the 3.07 will have lower rpm and better mileage than a 3.73 at the same cruise speed.
Your in town stop and go mileage may be similar between different gear ratios. It depends a lot more on your right foot than the axle ratio while you are working through the gears.
I had a 2.59 and at 70 it was only about 1700 rpm. If you are now at 2400 rpm you are spinning the motor over 40% faster and that is why your mpg dropped.
The higher numerical gears will help it accelerate better, but at the expense of fuel mileage at cruise.
The higher the rpm at your cruise speed the worse your mileage. So a 2.59 will have lower rpm and better mileage than a 3.07, and the 3.07 will have lower rpm and better mileage than a 3.73 at the same cruise speed.
Your in town stop and go mileage may be similar between different gear ratios. It depends a lot more on your right foot than the axle ratio while you are working through the gears.
I had a 2.59 and at 70 it was only about 1700 rpm. If you are now at 2400 rpm you are spinning the motor over 40% faster and that is why your mpg dropped.
