Drove my Brother's recently purchased 2005 Mustang 4 liter V-6 with a T-5 and made some interesting observations. The relationship between the engine rpm and car speed is almost identical to my slant with a t-5. It is turning 3500 RPM at 20 MPH.

So, I went on line and looked up its tranny ratios. If you can believe what is printed on line, this T-5 has the same 1st gear ratio as Lou's, and the same 5th gear but lists the "final drive ratio" as 3.55. I don't know for sure what this means, but suspect it means the rear ratio, and not 5th gear final drive. It could not mean final drive in 5th as this would indicate a rear ratio of 5.22 which would require a huge ring gear, and much larger pumpkin that the normal car rear.

In any event, it was interesting to note that the Ford folks set up their naturally aspirated 6 so that the first gear worked out similarly to what my slant has. The biggest difference is that the RPM drops off much more when shifted into 5th gear. A 3.55 rear when dropped by the 5th gear ratio of .63 yields 2.23. And, the tires are taller than my slant. I have 205 60 15's and the Mustang has 215 65 16's. So this car is going 60mph at 1800 RPM.

The published first gear ratio does not make sense to me. I bet the car my brother owns has a higher numerical 1st gear ratio than stated. But, I suspect the 5th gear ratio is correct.

His car did not feel quite as fast, but maybe that is just the lack of the turbo effect ,and the rush that comes with that. It is rated at 210 HP. And it ran very nicely. I was impressed, and glad to see some good engineering going into a six, RWD even if it is a V.

Sam

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Final drive ratio = rear end ratio

http://www.shadetreemechanic.com/ford_m ... _specs.htm

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That's exactly the web page I went to. The first gear ratio doesn't seem right to me though. Not based on the speed this car went in first gear with a taller tire. I will test drive it again and take more careful measurements. The bottom line is this v-6 Mustang has a very familiar feel when rowing through the gears. The Dart seems to have more torque in 5th, but that might be the turbo, smaller tires and higher ratio 5th gear. His car got real buzzy in 5th if you let the rpm drop below 1800 and tried to accelerate or keep the speed up a hill. The slant seems to pull that off much more gracefully. It will accelerate up hill in 5th at 1500 RPM without a groan or shudder. (Lou is grimacing right now.) And if you do need to shift down into 4th, the RPM's don;t jump up as high as in the Mustang.

One more thing of note. I really like the clutch in the Mustang. I am pretty sure it is hydraulic. And it was miles smoother than my dual friction disk. It would be fun to figure out if the pressure plate and disk are at all compatible with a slant flywheel.

I want to reiterate, his Mustang is a nice car. I was impressed. But I would not trade it for my Dart. I might add one though. (I didn't really say that)

Sam

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Thanks for your observations, Sam.

I think even as low as about 2.20:1 (axle * OD ratio) in 5th is fine in my Darts. Yes, shifting from 5th (0.63) to 4th (1.00) is a big drop, and vice versa. It's especially annoying at the end of a straight on the road course when you shift from 5800 RPM in 4th to 3600 in 5th and you're trying to pull uphill slightly at 115 MPH...

Lou

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Home of Slant6-powered fun machines since 1988

You need a T-56 six speed. It goes from .63 to .80. Perfect. wouldn't you say?
Sam

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The latest Mustang 3.7 liter V6 has 305 HP and has a six speed. The direct injection seems to be of great benefit for driveability and fuel economy. Ford engineers coaxed 48.5 MPG from the V6 using a single tank of gasoline.

http://www.youtube.com/watch?feature=pl ... ynLARk1kVA

Do you know the EPA mileage ratings of that combo?

Sam

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Other than Google results I know little about the new Fords. In the Mustang the 305 HP Ford V6 is rated at 31 MPG highway, the 5.0 V8 is rated at 26 highway with 412 horse power and 390 ft lbs torque. The 3.7 V6 is rated at 275 lb at 4,500 RPM in the F150, 280 ft lbs in the Mustang. The compression ratio is 10.5:1 http://www.ford.com/cars/mustang/

hi sages- dont think this is being explained correctly, unless meanings have changed. final drive ratio means the highest trans gear times the rear axle ratio or differential ratio. in my 76 feather duster the literature says it has a 2.94 axle ratio and a 4th speed od ratio of .73. multiplying that out gives a final drive ratio of 2.15, quite high by 76 standards. if the highest trans gear was 1 to 1 or direct , then the final drive ratio would be the same as the differential or axle ratio. this was common with old 3 speed manual transs w/o the electric overdrive. these new mustangs with the v6 , a 3.55 rear axle ratio and a .63 od top trans gear would yield a final drive ratio of 2.23 still a tall gearing for a 6 which accounts for the high gas mileage. am i right. thanks tons paladin

Your math makes sense, and is what I came up with. But, it assumes that their meaning of the term final drive, in this instance means the rear end ratio, and not the final drive ratio of 5th gear. Thanks for joining in.

Sam

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Ratio & final gearing could be looked at as two different numbers once tire diameter is figured into the soup. Where our older cars with much smaller diameter tries bolted onto a 3.55 rear will produce a different gearing effect than a Mustang sporting the same 3.55 and 18 inch or taller skins.

The reason the new Ford of comparable weight can handle the taller tire is its engine is a bit more powerful than our stock slant six. These new V6 engine’s output are equal to, or greater than, most of the small to mid sized V8’s of yester year.

Recently the not so big three have introduced still more powerful V6s than this example from 05. By the way, a 3.7L Jeep/ Dodge v6 has almost the same power output as the Ford V6, and is being replaced by the new [url=http://www.allpar.com/mopar/phoenix-engines.html]Pentastar V6[/url] this year.

From: http://cars.about.com/od/2001/ss/ag_ssx_05mustv6_5.htm

Test car: 2005 Mustang Deluxe V6 Coupe
Price as tested (including options): $22,055
Engine: 4.0 SOHC liter V6
Output: 210 hp @ 5300 rpm, 240 lb-ft @ 3500 rpm
Regular fuel: Regular
Transmission: 5-speed automatic
Drivetrain: Rear-wheel-drive

Curb weight: 3300 lbs
Trunk room: 12.3 cu. ft.
EPA fuel economy: 19 MPG city/25 mpg highway
About Cars observed fuel economy: 21.6 MPG

Remember today's hp ratings (ASE Net) are conservative in compairson to pre 1972's ASE Gross figures. I'm guesing here; figured the old way, flyweel with no accerories hp, that V6 would be puting out 300 hp. perhaps more.

As an example numbers from Foundationpc.com:

A pre 1972 318 V8 is listed as 230 HP @ 4400 rpm, 320 lb-ft @ 2000 rpm. After 1972 that same engine’s out-put rating was listed as 150 HP @ 4400 rpm, 260 lb-ft @ 2000 rpm including a 0.2 drop in compression ratio in the post 1972 engine.
So Sam, I can see where a modified slant powered “Aâ€￾ Body as yours performs comparatively to a v6 Mustang.

I wish there was a cost effective way to bolt on one of the newer 4 or 5 speed automatic transmission to our slants which could provide great performance, as well as long legged fuel economy out on the road.

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

interesting clarification wj and sam. actually you have brought upa term used with the oldercars only occassionally. while final drive(top gear ratio times differential ratio) and differential ratio(ring gear teeth divided by pinion gear teeth) are different , the term effective final drive is commonly used today and means the added effect of much larger tires. 15 16 and 17 inch tires and larger tread raises the final drive ratio above what the top gear and differential combined give. older tanks commonly had 14 inch wheels and some had 15. you would actually raise your final drive ratio by putting 8.25 by 14 tires on a car that called for 7.35 by 14 tires. did this on a 69 coronet and noticed a slight mpg increase but it was slightly more sluggish too so its all a tradeoff. paladin