3.73's and highway speeds

ninety15.0 · Sep 9, 2005

try driving a four cylinder car around at 2k rpm at 80 mph on the highway....no way it just wouldnt go...hell it probly wounldnt be able to maintain speed never mind go up and down hills without jumping down a couple gears. thats the difference...those cars cruise at 3500 because they have to.

blackstangt · Sep 9, 2005

first off, my four banger had the speedo topped out from NH to seNY state, It could put out enough power to go faster than i wanted to. It blew up driving up a steep hill at 65 after racing a beamer. My 5.0 is at 2000 rpm at about 80 mph, that makes 6k rpm 240mph, so I wouldn't worry about top speed for gear change on it, but it hurts highway mileage. I get 24+ mpg when driving normally, capable of about 26-27 if i drove it at optimum rpm. Engine wear would be greater per minute, hence rpm, but it is proportional to your speed in the same gear. If you are going 60 at 1500, 80 at 2000 is going to be the same wear per mile, because you will do that mile in less time. Therefore the only increase in wear is in the extra drag gained at a higher speed, but with an engine producing more power for less throttle at peak torque, it may be worth it to go faster to a certain point, where the torque dissapates and rpm is where the power is coming from. For the most part, holding a car at 2500rpm isn't bad, but you wont see me doing a constant 5500rpm in third on the highway because it hurts gas mileage and engine life per mile, and per minute as compared to a higher gear. As others were saying, it's not fifth gear that is going to hurt your engine, it's wot in 1st-4th.

cleanLX · Sep 9, 2005

Crawlin306 said:
I think, I am pushin 4200 at 70 w/my 3.90 (But my car is rarely ran on the hwy, nor ever ran on the street lol, only a few times I took it out for a long spin w/o my trailer, ok ok call me a trailer queen! but im the 1320 trailer queen!

What tranny are you running?
With 4.10's, I don't even see 3000rpm at 80mph on a 25.4" tall tire.

Anyone running 3.73's and leghumping the engine wear excuse is a hypocrate(sp?)
Go put 2.73's back in if it is a real concern.

Would I rather have an engine that spent it's life at 3000 or 2000, I don't care, it doesn't matter, which one had more cold starts/city driving would be my concern.
The one that spent it's life lubricated rather than jonny short trip is the one I'd take, be it 3000rpm or 2000rpm.

blackstangt · Sep 9, 2005

i agree cleanlx

5spd GT · Sep 9, 2005

cleanLX said:
Anyone running 3.73's and leghumping the engine wear excuse is a hypocrate(sp?)
Go put 2.73's back in if it is a real concern.

That is a horrible argument. I put in 373's instead of 4:10's. How is that hypocritical? I put in 373's instead of 4:30's. How is that hypocritical. I did that for some of the reasons above. wear and tear.

cleanLX said:
Would I rather have an engine that spent it's life at 3000 or 2000, I don't care, it doesn't matter, which one had more cold starts/city driving would be my concern.
The one that spent it's life lubricated rather than jonny short trip is the one I'd take, be it 3000rpm or 2000rpm.

You obviously missed the point I was trying to make.

Oh and to the others...I guess I've been in some rare 4 cylinders but they aren't all cruising at 3,500 rpm. Their potential top speed would be horrible with that kind of gearing. I don't buy that anyways. Most I have seen are 2,200-2,600rpm IIR. I've owned a 4 banger.

5th gear is more of a crusing gear...not a power gear. No need for "power" at a low rpm when cruising. Just enough to overcome aerodynamics and engine braking is all that is needed IMO.

cleanLX · Sep 9, 2005

5spd GT said:
That is a horrible argument. I put in 373's instead of 4:10's. How is that hypocritical? I put in 373's instead of 4:30's. How is that hypocritical. I did that for some of the reasons above. wear and tear.

If wear and tear is so critical, you should be running 2.73's. It's that simple.
I put 4.10's in rather than 3.73's or 4.30's on account of trap speed and pwer peaks/shift points. Had nothing to do with wear and tear. I would not hesitate to run 4.30's if that is what the car wanted.
And besides, I thought I'd get you much more wound up... I'm dissappointed. .

Every 4cylinder car I've been in in the last decade rev's up handy to 3000 at ~70mph.
With shortcommings in displacement, they rely on rpm to make power. Outside of caming and airflow to accomodate the higher rpm, there is no voodoo magic in the rotating assembly.
I'm sure the lighter smaller weaker parts they use are just as suseptable(sp?) to rod stretch side loading etc as our heavier stronger pieces.

The fact that our 'stockish' 5.0's are done making power at 5000rpm is not a function of the rotating assembly, it's a function of the cam/valvesprings, heads/intake.
There are plenty of stock shortblock hci combo's out there spinning up handy to 7000rpm... a frind of mine shifted his at 7200! Granted it was carb'd, but, stock rotating assembly. No fancy 4cylinder voodoo tricks.
It's not that the 5.0 cannot spin that high, it's that there is no need for it to given where it can and does make it's power.

Allforspeed · Sep 9, 2005

this post is starting to get pretty silly, 2 points i'd like to make

1. the "theoretically possible" life of a mustang motor if properly maintained is many hundreds of thousands of miles, my first lx had 175K miles, everything stock, never even had the headers off, didn't burn a drop and had led a life of abuse BEFORE i got it, and i tried to break that thing by powershifting and reving the hell out of it many times and it never broke once, point is, "10% more wear" is a statement that has no number one can come up with to figure out the life of a 5.0 before and after a gear swap,

2. i would bet, 1 hard trip to redline or one good burnout does more wear on everything on the car than an hour and a half of cruising at 2800rpm, if your worried about wear on the freeway and mpg, buy a cheap beater car, and dont ever rip your stang to redline and dont ever spin the tires, but if thats the issue than why the hell would you want ot own a stang??

btw: i have stock gears, but thats cause i like 26 mpg and a car that can quietly and comfortably cruise at 100mph if i feel the need, and most importantly cause installing different gears will cost me at least 400$

5spd GT · Sep 9, 2005

cleanLX said:
If wear and tear is so critical, you should be running 2.73's. It's that simple.
I put 4.10's in rather than 3.73's or 4.30's on account of trap speed and pwer peaks/shift points. Had nothing to do with wear and tear. I would not hesitate to run 4.30's if that is what the car wanted.
And besides, I thought I'd get you much more wound up... I'm dissappointed. .

Wound up? ha...lol. This is stangnet...opinions "count".

When did I say wear and tear was so critical? Show me. I simply put that a steeper gear will cause more engine wear...how can you honestly argue that point. 273's with my combo would be a dog (buck) on the highway. More variables than just gear selection here...

Is your car a daily driver? Should someone pick a gear based on trap speed/power or think about other variables? I don't think Ford does it that way...do they

cleanLX said:
Every 4cylinder car I've been in in the last decade rev's up handy to 3000 at ~70mph.
With shortcommings in displacement, they rely on rpm to make power. Outside of caming and airflow to accomodate the higher rpm, there is no voodoo magic in the rotating assembly.
I'm sure the lighter smaller weaker parts they use are just as suseptable(sp?) to rod stretch side loading etc as our heavier stronger pieces.

lighter smaller parts are better. That is why people (when they have money) go with lighter parts. Easier all together and help rev better as well. Think about it

I must be in these really rare 4 cylinders...I must get the "non-performance" axle ratio for every 4 cylinder I have been in or acustom too What a coincedence...

cleanLX said:
The fact that our 'stockish' 5.0's are done making power at 5000rpm is not a function of the rotating assembly, it's a function of the cam/valvesprings, heads/intake.
There are plenty of stock shortblock hci combo's out there spinning up handy to 7000rpm... a frind of mine shifted his at 7200! Granted it was carb'd, but, stock rotating assembly. No fancy 4cylinder voodoo tricks.
It's not that the 5.0 cannot spin that high, it's that there is no need for it to given where it can and does make it's power.

I know it doesn't have to do with the bottomend in that case. I never said it did...but I was showing you how ineffiecent it is/was to run your car that high of an rpm when your engine doesn't want to rev past 5,200rpm or so. Think about it!

cleanLX · Sep 9, 2005

lighter parts are only better when they are as strong or stronger that what they are replacing.
we are not going to compare a briggs and stratton rod/piston to a LS1 now are we.
Comparing the weight/strength of parts in a 1.8l motor to the weight/strength of parts in a 302 is not apples to apples.
Sure they are lighter, they'd also fail on break in with a 302 piston hanging off the end.

Daily driver... ok, lets go there...
'69 F250 390FE C6 w/ 4.10's and it's done making power at 4200rpm. No 5th gear, and 1000rpm less range than my mustang... which is not my daily driver.
I freeway drive and have road trip'd in my F250... as well as ran it down the 1/4 and hauled 4000lbs of gravel/sod.
I really don't see what my daily driver has to do with it?
Will it last as long as my mustang... I have no idea... but with the frequent cold starts, and short trips combined with towing and hauling, I should imagine not, I doubt it will be on account of sustained rpm under unloaded conditions tho.

Ford picks thier gears based on emmissions and gas mileage... not performance.
Should someone pick thier rear gears based on power and et's... Heck Yes.

wht93gtEd · Sep 9, 2005

Michael Yount said:
Most of you are too young to remember what it used to be like. Overdrive tranny's and really low cruising engine revs are largely a product of the EPA. As CAFE requirements got tighter, manufacturers achieved their highway mileage numbers largely with long rear gears. The fox bodies are a classic example -- a 2.73 gear with a .675:1 overdriven 5th. Not to save wear and tear on the engine - but to achieve a certain highway mileage number. Drop on back to the 60's when all the domestic cars were running 3 speed automatics (the vast majority) or 4 speeds -- top gear was 1:1. And a pretty standard rearend ratio was 3.00:1 or 3.23:1. The tires were a bit taller - but not much. (to compare that rear gear number to the Fox number - multiply 2.73X.675) The engines routinely saw MUCH higher revs under cruise. And they were aerodynamic slugs that weighed more which made the engine work harder to push them through the air at a given speed. And even with poorer oil, poorer machining and assembly, carbs/points (tuneups pretty much required every 6000 miles just to keep them from missing) -- cars routinely lasted 100K. Our 65 Olds Vista Cruiser had 156K miles on it when Dad sold it - still in very good working order. Many, many of those miles were put on loaded with 5 kids and luggage and spinning along at about 3000 rpm at 70-75 mph on the highway. And we weren't the only ones -- millions of other high mileage cars out there under similar conditions during that time period.

100% TRUE.....

My 74 Buick Apollo, with a Buick 350, has a GM Turbo 350 tranny (that's a 3-spd auto) with a 3.27:1 rear. I can tell you that I turn over 3k around 65...but my car's 31 years old, never been rebuilt, and it runs absolutley perfect. Why???

Because it was my grandma's car.

She drove it to the grocery store and the senior center, and back and forth to PA. It was never, I mean NEVER beat on. Romping on your car breaks engine parts, and causes them to not last, not a few hundred higher RPM's.

Sure, you can all make the argument that higher RPM's causes more engine wear. But is it enough wear to cause a problem? NO. If your car needs to be rebuilt at a 100k, then you have bigger problems. Any factory 5.0 should make it way past that. My friends 86 had around 215 when he blew the headgasket. And the only reason the headgasket went is because the car overheated and snapped a head bolt.

And to the person talking about 4cyl cars....almost all of them see over 3k on the highway. I have a 91 Mitsubishsi Mighty Max pick-up with the 2.0L 4cyl. To go 70 I have to keep it almost floored, and there's over 265k on the odometer! The most extensive work ever performed on the truck was changing the fuel filter. If you change the oil every 3k, many cars will last a very long time.

Michael Yount · Sep 9, 2005

The evidence is overwhelming -- the extra wear/tear on the motors is negligible. It shouldn't be a concern for anyone considering gears in cars like ours. Other things should be - but not wear/tear on the motor.

5spd GT · Sep 9, 2005

white93ed - So just because your mitsubishi has to be on the floor at 70mph means others have to be Umm...no. Many many many more variables than that. To say that 4 cylinders have to be over 3,000rpm on the interstate is silly...or saying that all have to be in that operating range is

MY- So where is the overwhelming evidence?

Michael Yount · Sep 9, 2005

All you have to do is read the thread for the evidence 5 spd - but you're not having it; it's ok, I've come to expect it from you.

The vast majority of 4 cylinder powered cars are revving 2500-3500 rpm at highway speeds. Generally, the 6's are revving higher than the V8's as well. My wife's car is at 3400 rpm at 70. I've rented (business) too many 4 and 6 cyl. cars over the years to count - I can't think of one that doesn't rev much higher than a 5.0 w/stock gears at highway speeds. It's those cars (literally millions of them on the road) that put on relatively trouble-free 100, 200, 300k miles with highway revs like that. The increased revs under highway cruise are simply a non-issue when it comes to wear and tear. The engine's just not working hard enough to do any significant damage. The 'evidence' is all around you on the road every day. And they've sold WAY more of the higher revving engines in the last 20 years than V8's. All of them out there - revving higher with no problems due to increased engine speed.

And the V8 is loafing even more -- the 4's and 6's are working harder -- putting out a larger percentage of their max HP at the same cruise speed as similar cars with V8's.

Lots of reasons to pick a certain gear - but 3.73's in a Stang aren't gonna cause any significant additional wear and tear on the engine under cruise. And running it at 3000 instead of 2500 won't either.

5spd GT · Sep 9, 2005

Whether you expect it or not - doesn't effect whether or not higher revs cause more wear.

It does cause wear...I've seen ya'll change the adjectives a bit during this discussion...so now it is not "any significant additional wear and tear"...all the way from it is negligable. Hmm...

Michael Yount · Sep 9, 2005

It's been that way from the very beginning of the thread 5 spd -- you're just not listening. From the beginning the language has been the same. More wear? Yes. The pistons/crank/rods/cams/lifters/etc. are moving faster. Is the wear significant or worth considering vis a vis the longevity of the engine? No, it's not.

You've been so busy telling us 'there's more wear' that you've completely missed the more important issue. Whether that wear is significant or not. It's not.

5spd GT · Sep 9, 2005

Michael Yount said:
It's been that way from the very beginning of the thread 5 spd -- you're just not listening. From the beginning the language has been the same. More wear? Yes. The pistons/crank/rods/cams/lifters/etc. are moving faster. Is the wear significant or worth considering vis a vis the longevity of the engine? No, it's not.

You've been so busy telling us 'there's more wear' that you've completely missed the more important issue. Whether that wear is significant or not. It's not.

Wrong...

I will break that down later

I never said it was significant...why are you playing that game? I said you get more wear...any argument

Mustang5L5 · Sep 9, 2005

It all comes down to this.

X = Increased wear due to engine RPM increase

Y = Decreased wear due to reduction of load on engine due to mechanical advantage

X + (-Y) = ???

Without research it's impossible to know what the trade off is. All you can do is speculate. There are arguements for both aspects

super302 · Sep 9, 2005

5spd GT · Sep 9, 2005

super302 - You didn't even edit

I miss your "old" signature

Mustang5L5 · Sep 9, 2005

5spd GT said:
super302 - You didn't even edit

I miss your "old" signature

It doesn't show his edit, but i just got the reply confirmation email with his post pre-edit.

I know what he said

3.73's and highway speeds

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