Are the three inch half shafts used on 74 and newer models a direct fit on my 73?

Thanks in advance!

 

Yep

 

Yes but they are not any stronger than the 2 1/2 ones. The tubing is thinner but larger. They are about the same strength. If you have them go ahead and use them but don't expect them to be stronger.

 

No kidding. No stronger? Why did the General make the change?

 

Wrong, they are stronger. The larger 1/2 shafts came along with the introduction of radial tires on the Vette and a decision was made to increase the strength of the suspension components at the rear. I just "love" seeing NCRS type Vettes at local shows witht he "big" 1/2 shafts on them (don't dare tell the owners about it, most of them are already self proclaimed "experts" on the Corvette.)

 

Cut one in half. The wall is thinner. They might be marginally stronger but if you are going for high horsepower I would get some better half shafts.

 

I believe the 2 1/2" shafts are .125 wall thickness and the 3" shafts are .120. Not much difference.

 

Who makes a reasonably priced aftermarket half shaft that's stronger than either of the GM parts?

I'll be pushing 550 flywheel ponies through a four speed, 3.70's, and sticky tires.

Thanks,..you guys are great!

 

 

it is not so much the half shaft but rather the U joints you should be concerned with.

But Van Steel has some nice composite half shafts. Sorry just now noticed reasonably priced. I think you get what you pay for. But with the composite half shafts they are strong yet very light but are by no means cheap.

You can also purchase the 3" half shafts new from Dragvette and you should also consider there half shaft loops as well. They come with the heavy duty spicer U joints installed at a reasonable price.

 

Not much difference in thickness or strength. Sounds like the 3" would be a little stronger.

 

torque amounts to force times radius.

the average engine may develop 400 ft (times) pounds

ie you would need a 400 pound weight at a 1 ft radius to develop that torque. Or a 200 pound weight at 2 ft radius or an 800 pound weight at 0.5 feet radius ect.

after torque multiplication at the rear end say 3:1 ratio you have 400*3=1200 ft pounds at the half shaft.

The force in the metal in the half shaft with a 1" radius would be multiplied 12 times ie 12"/1" to get 12*1200 = 14,400 pounds.

The force in the metal in the half shaft with a 1.5 radius would be multiplied by 12"/1.5" ( 8 ) to get 8*1200 = 9,600 pounds.

The metal skin of the 3" shaft undergoes 50% less stress.

 

Turtlevette is correct. The 3" shafts are way, way stronger than the 2 1/2's.

With everything else being equal, a shaft of greater diameter is stronger. Always.

 

It is actually 12/1.25 = 11520 vs the 9600 pounds. If you wanted to get real technical you would have to take in the thickness of the shaft and the type of steel being used. I agree with you that they are definitly stronger but 50% stronger no way. I would not want either one behind a 500+ HP motor with slicks. I have seen both of them twisted like a pretzel.

 

i'm sorry, your right i was thinking 2" instead of 2.5.

1.5/1.25 = 1.2

the 3" shaft is 20% stronger.

 

 

I'm no metalurgist nor math whiz ... but taking the 3" shaft being 0.005" thinner into account also, it seems the 3" shafts are no more than 16% stronger.

 

I agree with Clifton I have run some pretty healthy BBs over the years, all with the 2.5" half shafts. Broke a half shaft U-joint on two different occasions and twisted a transmission tailshaft yoke off once. Boy, that broken yoke was a wild ride Did a power shift from 1st to 2nd when it cut loose. Before I knew it I was facing the other way looking at where I came, still sitting in the middle of my lane......nothing else damaged

Bullshark

 

The dia. is larger and they may be slightly stronger, I would not rely on just a larger dia. shaft to solve any problems. You can strengthen the rear up with solid u joints, and don't forget the safety loops for some added security....

 

Thank you BullShark . But as mentioned before please get the half shaft loops that DragVette has. If you think breaking a half shaft or a u joint is expensive wait till that thing breaks and takes out your battery box or glove box behind your seats.

Just remember HP will find the weak link no matter what you do. That being said you can run normal street tires so they will spin before you break anything. If you run slicks or sticky comp street tires then you will start to break stuff if launched hard. To help this a bit you can get the DragVette setup which will help to keep the half shafts level during launch to put less stress on the U joints. Also you can purchase a much stronger rear spring to help with the drop say a 360 to 420 or heavier. You can also get new rear suspension bump stops and shim them where the rear will not go down very far before hitting the stops. After this you get into real money. Look for Toms Diffs and you can get an idea of the cost such as a 12 bolt diff and all of the parts for the upgrade. Oh and make sure you sit down first lol.

On a personal note of my .02 lol. The Corvette was not really designed as a drag car but a sports car which means corners. . The IRS is great for this but when drag raced it is not really up to the task unless you spend big bucks. So if you want to drag race and spend less time messing with broken stuff start with something like a Camaro or Nova or a Vega with a solid rear axle. Some replace the IRS with a solid rear axle to race but to me if you do this it is no longer a Corvette just a pretty Camaro lol.