I am looking on getting a new 3rd member for my 9" rear. I want something good on the streets but also good on the highway. Probably street driving, 75% of the time and the other on the highway. I am thinking about either 3.50 or 3.75 or 3.89. It will be posi and have around 400+hp. Planning on a 5 speed manual transmission, 17" wheels. What would be best? thanks.
Yeah I was leaning towards the 3.75, but considering the 3.89. My first coice was 3.50, but now it's between 3.75 and 3.89. Is there that much of a noticeable difference bewteen the 3.75 and 3.89?
Posts: 2035
Joined: 9/5/2006 From: Barossa Valley, South Australia Status: offline
you might wanna consider some decisions on the 5 speed before the rear end. sorry if you're already a step ahead of this
2 things
1) you want the box that can handle your [unspecified] torque (which may or may not be a standard T5)
2) you want to know the ratios, particularly for 1st and 5th.
examples
too low ratio 1st with a 4.11 means early change (eg '84 SVO T5, engine at 5000rpm = 21mph). too high ratio 5th with 4.11 means still revving fairly high at highway speeds (4.11 with 0.87 5th = 3.57 final drive). too low in 5th with 3.75 means less pull in 5th (3.75 with 0.69 5th = 2.58 final drive)
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A 2007 study found on average Australians walk 900 miles a year. We drink 26 gallons of beer. That means, on average, Australians get about 34 miles per gallon. Not bad hey!
I'm not sure what exact transmission I will be getting, other than the fact it will be a 5 speed with overdrive. I guess I'll have to find something that will handle the torque and get the gearing right. The torque will be somewhere in the same range as the hp, 400-450 or so. I assume there is a transmission that will fit my application?
I have the T5 with 3.50's in my nine inch and I really like it. First gear is just a little low for my liking but the engine runs at 2200 rpm on the highway in 5th doing around 75mph. Really low gear sets like 4.11's are not the best choice for a standard trans IMO. With an auto they are ok because the trans will shift for you.
Low gears are good for manuals if the transmission has the right gearsets in it. You need to know what trans you're gonna run and what the gears are before you get a ring/pinion set. If you go with 4.11's and have a trans with something like a 3.33 1st, you'll have a totally useless 1st gear on the street or on the track, no traction whatsoever not to mention shifting outta first about 0.5 seconds after the clutch is engaged. Too high a diff gear with too high an o/d and you may not be turning enough rpm on the freeway to use 5th without bogging the engine somewhat(dependant upon the engine build) unless you're speeding. Try explaining to a cop why you were doing 85 in a 65 zone because of your gearing, I doubt he'll have sympathy for your plight.
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Who cares how much horsepower it has, all that matters is how fast it goes!
Best run 13.23 at 106.97mph with a 2.183 60' Times from before tune and driver mod.
The G-Force T5 kit has a 2.94 1st, 1.94 2nd, 1.34 3rd, 1.00 4th, and an optional .59 or .73 5th gear. When I get to it I'm probably going to opt for the .73 5th to narrow the gap between 4th and 5th. Freeway mileage is not a huge concern for me:) Won't be any worse than it is now, turning 3300 @ 75 with my 3sp.
Tranny ratios, wheel and tire size, will come in to play. For me, I have both 3.70's and 3.50's in cars and for highway use, the 3.50 is my favorite, more so when hooked to a tremec tko with a .68 final. It helps if you have some hp to push these along.
I'm looking at maybe getting Richmond's new 5 speed at some point, it has a .77 5th and 3 different 1st gear ratios. I also like the 2nd and 3rd ratios a bit better. With a 3.70 gear and a 26" tire, .77 o/d puts you at around 2,500rpm at 70mph. Not bad, especially pulling out with a 3.06 1st gear.
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Who cares how much horsepower it has, all that matters is how fast it goes!
Best run 13.23 at 106.97mph with a 2.183 60' Times from before tune and driver mod.
a couple of calculators which you may find useful.
my tip is to be realistic about where and how you drivemost of the time...no point in choosing ratios that will give you a 180mph top speed if you drive from light to light!!!
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quote:
A 2007 study found on average Australians walk 900 miles a year. We drink 26 gallons of beer. That means, on average, Australians get about 34 miles per gallon. Not bad hey!
Posts: 2035
Joined: 9/5/2006 From: Barossa Valley, South Australia Status: offline
my use is fantasy only...i'd love the extra cog in my mustang, but just cant justify the expense.
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A 2007 study found on average Australians walk 900 miles a year. We drink 26 gallons of beer. That means, on average, Australians get about 34 miles per gallon. Not bad hey!
I am thinking about the g-force t-5 tranny. I will drive it mainly in town, occasionally on the highway. I am not considering 4.11, too high, but 3.75. I'm not considering top speed either, but quick acceleration, but not to where I am shifting an 18 wheeler.
my tip is to be realistic about where and how you drivemost of the time...no point in choosing ratios that will give you a 180mph top speed if you drive from light to light!!!
I don't get this forum when it comes to gears. A 4.11 gear is not a high gear it is a low rear. Everyone on here seems to think that a high number is a high gear. A high number is actually a low gear not a high gear. The higher the number the lower the gear. Ratios are like fractions, 1/4 is lower than 1/2 just like 4.11:1 is lower than 2.79:1.
Posts: 2035
Joined: 9/5/2006 From: Barossa Valley, South Australia Status: offline
quote:
ORIGINAL: racin66coupe
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ORIGINAL: Aussie66Fastback
my tip is to be realistic about where and how you drivemost of the time...no point in choosing ratios that will give you a 180mph top speed if you drive from light to light!!!
dont mustangs try to lift off at about 165
mine is doing the cessna hop at about 115. Maybe the weight of a big block would hold it down?
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A 2007 study found on average Australians walk 900 miles a year. We drink 26 gallons of beer. That means, on average, Australians get about 34 miles per gallon. Not bad hey!
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3.50??? or another??? - 
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...i'd love the extra cog in my mustang, but just cant justify the expense.
