Well I am a bit surprised how important the ring and pinion setup is in realation to getting power to the wheels. I thought it was mostly to avoid noise and wear.
I've got the 3.07s in and its defenity putting alot more power on the ground then the 2.94 that where setup wrong. The 3.55s I could burn the tires about 10 feet. The 3.07s I can burn them about the same, maybe 8 feet. But the 2.94 I could only get a chirp out of them. As you can see, there is a pretty big jump from the 3.55 to the 3.07 and a very small one to the 2.94s. The only thing that was changed was the gears and it seems that the 2.94 was burning power because of the wrong setup.
Does this seem plasiable?

PS The gear oil looked like liquid crome in about 500 miles with the 2.94 when we dumped it.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

When picking your gear ratios if you have a good shop, they will help you figure out what might be 'better' if they know what they are doing...

Things that come to bear are:

Your vehicle weight
Tire size
Driving style
Transmission Ratios
What Axle you are working with (some axle designs eat a bit more power than other kinds... there has been some specualtions about how much an 8.25" and a 8.75" rob out of your flywheel HP vs the regular 7.25" )...

It's interesting to compare a light car moving with a mileage ratio vs. say the heavier car with the drag ratio...

There are reasons why Doc recommends your tranny ratio times the rear gear ratio in first gear be in the 10-11 range... I have noticed that 12 is kind of granny and burn outs are cool, but the drop in a wide ratio tranny to 2nd is not so nice...like wise anything in the 9ish range without the assist from a heavy torque band tends to just 'slug' for a few seconds until the car actually moves and overcomes rolling resistance....


-D.Idiot

Sounds like the 2.94s were self destructing and eating a bunch of power.

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Joshua

A rear has to be almost locked up to make any appreciable difference in power to the ground.

I did a Corvette for a buddy years ago. We used a 4.10 center section from Mid-America Corvette (BIG $$$) You would actually have to push the car to get it to roll downhill. I changed the gears and set it up myself and the car would roll almost effortlessly. We figured it would pick up a ton at the track. It didn't even pick up .02.

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Official Cookie and Mater Tormentor.

A ring and pinion is a hypoid gear... Depending on the gear ratio, it could take a lot more energy (pushing) to have the ring gear drive the pinion gear, than when the engine is rotating the pinion gear to drive the ring gear.... (think worm gear as an extreme example where power can only be transmitted one way)

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

Yup. A number of years ago, back before I figured out that it was stupid to waste time arguing on Usenet *ahem*:oops: , I got in it with an idiot who claimed to have lost 15 mph top speed from his Valiant just by switching from a 7¼" rear axle to an 8¼" rear axle with the same ratio. His explanation for this was that the 8¼" was much bigger and heavier and therefore, because of the bigger gears and bearings and such, absorbed a lot more power. I pointed out that if the rear axle were really dissipating the amount of power he was talking about, to slow down a Valiant by 15 mph, then the whole rear axle would be a white-hot lump of smoking slag after so much as a quick trip to the grocery store for a carton of ice cream. He wouldn't have it, and stuck to his claim. *shrug*

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I have a larger rear end now and find my top speed is somewhat limited....a few less ales might help.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

If that rear end is costing you that much drag I would also expect frost bite if it were hanging out too long.

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Joshua

Not really a lot more, no.
Right, but hypoid gears are not the same as worm gears.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I was just trying to think why it was harder to push
Have you've seen some of the pinions for trucks............

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

I understand what you are trying to say, but we are talking about a relatively small car diff here.

One other thing you have to remember, if the ring and pinion were set up so there was that much friction as to create a big horsepower loss, the rear would be burning itself up with heat damage.

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Official Cookie and Mater Tormentor.

I am certainly no expert on this subject. About all I know is that a larger gear ratio means quicker "off the line", and slower highway speed.
My Volare seems to get a little bit better gas mileage around town with the 3:55 gear ratio 8 & 1/4 diff, compared to the stock 2:74 ratio 7 & 1/4 diff, does that sound right?

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318

Sounds right to me, however, you will loose MPG on the highway with
that set up since the engine is turning much higher RPM
(as a general rule).

Engine RPM, trans output, rear gears all need to find a balace
for what your using the car for....
Stock engine, with 833od 4sp, with 3.55, 14" tires- works well because it
keeps the engine in the mid 2200 to 2500 rpm range which is
its best power range for normal driving (stock engine).
Use a 3.23, or the like, and 4th od gear is way to high to get good
ecom--- but that can work good if your trans is just 1 to 1 out put...
294 becomes a good highway gear 1 to 1 trans out put, but starts
to becomes a little tall for around town depending on the lower
trans gears (rim/tire size also plays part here) .

It all depends on your use what will work best...

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http://imageevent.com/jeffc
62 D100 225 3sp lwb
64 D100 A318 727pb custom lwb
66 D100 A318 4sp lwb
68 D100 B383 727 swb
65 Belveder A318 727 4d
65 Dart GT LA273 2bbl 904
73 Scamp 225 2bbl 4spOD
Old iron or no iron

Which kind of is anathemic since the Feather Duster/Dart Lite both used the 2.94 rear gear with the A-833 OD...(with a one barrel, and a honker timing curve, and some EGR to knock the knock back, and the bigger exhaust...and you could only use the OD when the speedo hit about 55 in 3rd...but it did get good gasmileage, in a 3200 lb car...)

It all depends on how you pick the parts to make the system work better...

-D.Idiot

It's all a matter of leverage. A long lever requires less effort to move a given mass but also requires a longer input motion for a given output motion. Gears work exactly the same way. A lower gear ( numerically higher ) will require less engine torque to get the mass of the car moving but will require more turns of the driveshaft to move the car a certain distance. A higher gear ( numercially smaller ) will require more engine torque but will move the car the specified distance with fewer turns of the driveshaft. It's all about leverage.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.