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Discussion Starter #1
Hey, just out of curiosity... dose anyone know at lets say 80, what the rpm is for 373s and 390s and how many miles per gallon aproxx do each one get as a daily driver.

thanks
 

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With 3.90s at 75 mph on stock tires, I turn about 2500 rpm in 5th.

Try these calculators to figure rpms and speed.

http://www.hardcore50.com/members/calculators.htm
(Hint: stock tire diameter is about 26 inches.)
- or -
http://www.allfordmustangs.com/Detailed/608.shtml


edit:I seem to be getting about 20mpg in mixed driving with my 3.90s -- about the same as I was getting with the stock gears, but because the RPMs are higher, I been driving 70-75 on the highway instead of 80-85 which is probably giving me a little better mileage.
 

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Discussion Starter #3 (Edited)
oh thats not bad with stock gears at 80 i am doing about 2000 flat +/-
i am not sure i am still debating which gears to run.
i am averaging about 21mpg flat... with a very very ... VERY light foot 22 i broke once so 20mpg dont sound to bad.

What quarter mile time are you running with that gears. how much did they cost.. i know mustangtuning has them for 150 so let me know
thanks

p.s. do i also need to buy the master bearing install kit or the regular install kit.????
http://www.mustangtuning.com/motive390.html

this is what i am looking at. How much did it cost to get them installed.
 

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Depends how many miles you have on your car as to weather you need the bearing kit or not. I think if you under 50k or so you should be fine.
 

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Discussion Starter #5
i have about 37600miles on my car, i definately need the regular 39dollar install kit correct? should i go out and get the bearins while the end is open ?
let me know
 

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When I got mine installed the mechanic said above 60K he recommends them but it's up to you you could go 100k pretty easily I think. i just said 50k before cuz I figure if you got more than that you might as well replace the bearings and start over fresh in the rear.
 

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Discussion Starter #7
Ok cool, at stangtuning.com

http://www.mustangtuning.com/motive390.html

you can purchase the install kit, i have to buy that if i take my car to have the gears installed correct? its the 39dollar option on that site.

thanks let me know

p.s. yea i thought i should get the bearings but i think i can go longer.
 

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I bought my gears at Mustaing Tuning. I didn't get the install kit -- after talking to my mechanic, he said he could get the parts he needed for less. My car only had 33000 miles on it so didn't need bearings and all. He charged $20-30 for the misc parts so it saved me a little there. Plus you need new gear oil -- $40 for synthetic. Labor was $200. So all tolled, I paid $150 for the gears and about $260 or so for install including parts and labor.
 

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i got my FRPP gears from www.buyfordracing.com for about $160.00 shipped to my door....i would get new bearings while the rear end is open.....the shop where i got an install quote from recommended anyone with more than 30K miles to install new bearings.....let us know what gears u decide on
 
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