joelliott said:Whats a good rpm to run HW speeds at? You above say your pushin 2300 at 70mph. I would have that thatd be kinda high. I run about 1850 at 70-75 with my stock 3.08 rear. I wanna go 3.73 being I have a 85gt with T5. I am thinking itll put me about 2300 too at 70-75. Is this ok on a pretty much stock 5.0.?
Joe E.
5spd GT said:Yours isn't a daily driver...
There are a couple guys on here like willys1 that actually lost time on their bolt-on stang when they went from 373's to 410's...it is to much for the stock breathing motor...and the way the autos drive ratios are...
410's will hurt gas mileage more and more wear on the engine (a higher constant rpm)...
I do agree...stick with the Ford gears...
Go with 373's...with YOUR car...
EXTRPR50 said:WHY NOT CONSIDER MOTIVE GEAR'S 3.90?
I DONT KNOW MUCH ABOUT MOTIVE GEAR, BUT IT IS AN OPTION...
PhLoBuS said:I know seriously if your going to buy a v8 what do you expect? great gas mileage?
Michael Yount said:5spd - yes, of course more gear means more revs; the relevant question is whether or not the increase is significant. There's a 10% increase in engine speed moving from 3.73's to 4.10's. Let's put that in perspective by talking about how that effectively racks up 'miles' on the engine. A 3.73 geared car will cover 250,000 miles on the same number of revs that a 4.10 geared car will use to cover 225,000 miles. I don't think that difference is gonna be significant in the life of the engine - at least as a practical matter.
As for all the talk about mileage - it's WAY more complicated than simple increasing revs, or my favorite - it's been proven that the difference is only 1 mpg. The fact is that the amount of power required to move the car through the air at a given speed (let's assume flat terrain for a moment) is fixed. It doesn't matter what gear you're in or what gear's in the rear -- the amount of HP required stays constant. The amount of airflow through the engine is not just a function of rpm, it's also a function of throttle opening. Because at a fixed cruise, the engine only has to produce a VERY small fraction of maximum power available at that rpm. At a fixed 70 mph, it probably only takes something on the order of 30-40 HP to keep the car moving. So, let's say the 3.73's are at 2000 rpm at that speed. With the 4.10's you'll be at 2200 rpm. But since the amount of power being produced is the same, the throttle opening will be slightly smaller with the shorter gear. So you can't simply conclude that at higher revs - you'll move more air and that'll take more fuel. That argument would indicate more power is being produced - but it's not; because speed is fixed. And power produced is a function of the cruising speed, not the rpm level. Power AVAILABLE is a function of the rpm level. It's likely that more fuel will be consumed, but the percentage will likely be less than the % of gear increase.
You're gonna have to check if you want to see how fuel mileage is affected by rpm in your car. I did some experiments in my wife's car with the trip computer on extended runs -- running in 4th gear and then 5th gear at different road speeds. Her car has about 15% difference between 4th and 5th gear. That's almost identical to the difference between 3.55's and 4.10's. At 60 mph, it used 5% more fuel; at 65 mph it used 7% more fuel; at 70 mph it used 10% more fuel. Her car is newer and fairly aerodynamic - the differences might be slightly greater in an older Stang.
Sure people may say 4.10's but in the end for some it is too little of a gear. Of course we always want the best and for overall speed it seems to go hands down to the 4.10's. But you always sacrifice something and i'm sure that it really is a lot of fun with those gears on quite a few applications, but for others it is a little, overboard. I personally don't think 3.73's are a disappointing gear for an aod at all, both that and 4.10's are a fine gear for a stock 5.0. It is all preference really on what you want your car to do and how you drive it. I have heard many people happy with their 3.27's or 3.55's, so does that make them in the wrong? Of course not, it is what makes them happy and what it takes to make someone happy and pleased with what they have is different for everyone and in almost any case, it will vary all the time - it's all preference.Grn92LX said:I agree with Michael. I dont, however, think that 410's on the highway are gonna 'kill' mileage. Possibly could see 1 maybe 2 mpg less but i'd say the fun factor of going from a 273 to a 410 more than makes up for that slight loss. I'll have to ask my friend what kinda mileage he gets in his near stock AOD 87 GT with his 410's. I'll ask my other friend with the h/c/i 306 if his mileage got worse going from 373 to 410. Both drive their cars everyday.
Tothe original poster, you WILL be dissappointed with 373's in an aod car. I suggest you make a post titled soemthing like 'stock/near stock aod guys, what gear you running/what gear you suggest'. garantee at least 75% say 410
I agree with both of you guys in a respectable sense. The main thing I see though is the fact that to do the same speed with either gear will require a different rpm. It's I suppose more freed-up "parasitic drag" from the engine because it is easier for the engine to rev under loads. I also however see the weights of these cars and by today's standards these are definitely not tanks are heavy luxury vehicles/SUVs where it takes a lot of force to get them going. I mean come on, we're talking about a 3000 pound aerodynamic car strapped to a 5 liter V8 - does anyone else see the easy time a vehicle such as that has in getting rolling on a normal basis? It isn't a great load on the engine in the first place really. The differences between the 3.73 and 4.10s is minimal however but nonetheless - they are there. Picking the RIGHT gear IS a science. If you want the best for performance overall then only you can be the deciding factor. No one can sit there and tell you without a unanimous decision of what to get because different people will always say something different. No one can choose for you what you want but yourself - the final decision lies with the owner - always.5spd GT said:I still stick by my side which is 373's are a better overall gear for performance and street......hmm...maybe even 355's...
I think the 373's and 410's at a cruising speed (70 for example) wouldn't take any more "noticeable" gas to keep it moving at that same constant speed...if any at all...the "fake" torque produced by the either gear ratio (373's or 410's) is enough to keep the "show on the road"...273's to 410's is different of course...
87'GTstang said:No one can choose for you what you want but yourself - the final decision lies with the owner - always.
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