Norwood

[Sieg]

Originally Posted by Track Junky

Told ya

Please tell me the finishing touches or just come up and show me how. Lodging, meals, K9 companionship, and beer is on the house.

[Track Junky]

Originally Posted by Sieg

Please tell me the finishing touches or just come up and show me how. Lodging, meals, K9 companionship, and beer is on the house.

Sheeeeet........Wish you were close enough to make the drive. Hate to say it but if its not the trans it has to be the amount yoke sticking out of the trans. My follow up fix would be the correct length drive shaft. My brother-n-law just bought a truck load of stuff from Amir Rosenbaum(old owner of Spectre) and one of the items was an aluminum drive shaft. I could talk him into given it to you for cheap if your interested.

[GregWeld]

Originally Posted by Sieg

If it was alright previously?

It might not have been previously alright -- but the old bushings -- might have been partially covering it up. Now you put some good bushings in that are transferring the motion of the ocean and so on.

My point wasn't that it was bad previously BTW -- My comment was more about that the minute I thought I had a drive shaft issue -- the first thing I'd have done was taken it to a shop and had the balance and Ujoints checked... BEFORE I made 53 adjustments to the pinion angle. :>)

[Sieg]

Originally Posted by Track Junky

Sheeeeet........Wish you were close enough to make the drive. Hate to say it but if its not the trans it has to be the amount yoke sticking out of the trans. My follow up fix would be the correct length drive shaft. My brother-n-law just bought a truck load of stuff from Amir Rosenbaum(old owner of Spectre) and one of the items was an aluminum drive shaft. I could talk him into given it to you for cheap if your interested.

Size matters!

Norwood is 45.25" from end of output shaft to bolt face of the rear yoke.

[Track Junky]

Originally Posted by Sieg

Size matters!

Norwood is 45.25" from end of output shaft to bolt face of the rear yoke.

Give me center to center of eyelets and give me an idea of what size you will need from center to center. Don't think he sold it yet but I'll shoot him a text right now.

[Sieg]

Originally Posted by GregWeld

It might not have been previously alright -- but the old bushings -- might have been partially covering it up. Now you put some good bushings in that are transferring the motion of the ocean and so on.

My point wasn't that it was bad previously BTW -- My comment was more about that the minute I thought I had a drive shaft issue -- the first thing I'd have done was taken it to a shop and had the balance and Ujoints checked... BEFORE I made 53 adjustments to the pinion angle. :>)

But it cost me $75! That's 15 hours labor in my shop!

It was only 12 or so........

Without a doubt the rear eye leaf bushings have had a noticeable difference of the feel of the car. More so than I ever imagined. Besides the lateral cornering improvement the car is tracking differently on the freeway now (increased sensitivity and following contours) and I suspect they're the reason.

I also checked the rear yoke for lateral movement between the end stops, there's about a 1/32" an inch, 3/64th absolute max.

Now to determine if the driveline length and/or pinion angle is the remaining source. The driveline shop didn't think the length was an issue though I still think another 1/2" would be ideal......FWIW. He also spoke very highly of Roy's Differentials who did the gear swap.

[GregWeld]

I wouldn't get too hung up on the 1/32nd of an inch....


Think about what the ujoints are there for... the rear end is going up and down like a friggin yo-yo... it's moving side to side... it's got one wheel up and one wheel down with roll... and the motor is shaking around on it's rubber mounts and ditto the transmission. In other words -- there's a whole lotta moving going on...


In your case - it might be a Whole lotta Shakin'... but that's an Elvis problem.

You might never find the last harmonic going on. It could be the trans - it could be the flywheel... it could be a wheel and tire -- and it could be a whole combination of things rotational.

The thing is -- you've been able to move the harmonic around - up or down the RPM range... with your pinion movements - so you would think it's drivetrain related...


Now we'll get into something that is actually drive line related... which is the type of driveline you're using versus the actual rpms it's running at. I can't remember all the detail -- but you have to calc your rpm's that the driveline is running at -- and the diameter of the shaft needs to be matched or you get a harmonic set up.

Damned if I can remember what it's even called -- or where I've read about it -- etc but it's there somewhere on the Internet. And it may be something Ron Sutton knows about - or someone else on here.

[Sieg]

Originally Posted by GregWeld

I wouldn't get too hung up on the 1/32nd of an inch....


Think about what the ujoints are there for... the rear end is going up and down like a friggin yo-yo... it's moving side to side... it's got one wheel up and one wheel down with roll... and the motor is shaking around on it's rubber mounts and ditto the transmission. In other words -- there's a whole lotta moving going on...


In your case - it might be a Whole lotta Shakin'... but that's an Elvis problem.

You might never find the last harmonic going on. It could be the trans - it could be the flywheel... it could be a wheel and tire -- and it could be a whole combination of things rotational.

The thing is -- you've been able to move the harmonic around - up or down the RPM range... with your pinion movements - so you would think it's drivetrain related...


Now we'll get into something that is actually drive line related... which is the type of driveline you're using versus the actual rpms it's running at. I can't remember all the detail -- but you have to calc your rpm's that the driveline is running at -- and the diameter of the shaft needs to be matched or you get a harmonic set up.

Damned if I can remember what it's even called -- or where I've read about it -- etc but it's there somewhere on the Internet. And it may be something Ron Sutton knows about - or someone else on here.

Thanks to Blake's mention of Mark Williams........

Critical speed is the speed at which a spinning shaft will become unstable. This is one of the single largest factors in driveshaft selection. When the whirling frequency and the natural frequency coincide, any vibrations will be multiplied. So much that the shaft may self destruct. Another way to think of this is that if a shaft naturally vibrates at 130 times a second, and one point on the shaft passes through 0 degrees 130 times a second (7800 RPM) then the shaft has hit a critical speed. There are several ways to raise the critical speed of a driveshaft. You can make it lighter, stiffer, or increase diameter without increasing weight. This is the reason carbon fiber makes a good driveshaft, it is stiff and light and can be made to any diameter or wall thickness. Aluminum, while it has a very good critical speed is not quite as strong as steel. Steel, with good strength characteristics will have a lower critical speed.

[intocarss]

Originally Posted by GregWeld

I wouldn't get too hung up on the 1/32nd of an inch....


Think about what the ujoints are there for... the rear end is going up and down like a friggin yo-yo... it's moving side to side... it's got one wheel up and one wheel down with roll... and the motor is shaking around on it's rubber mounts and ditto the transmission. In other words -- there's a whole lotta moving going on...


In your case - it might be a Whole lotta Shakin'... but that's an Elvis problem.

You might never find the last harmonic going on. It could be the trans - it could be the flywheel... it could be a wheel and tire -- and it could be a whole combination of things rotational.

The thing is -- you've been able to move the harmonic around - up or down the RPM range... with your pinion movements - so you would think it's drivetrain related...


Now we'll get into something that is actually drive line related... which is the type of driveline you're using versus the actual rpms it's running at. I can't remember all the detail -- but you have to calc your rpm's that the driveline is running at -- and the diameter of the shaft needs to be matched or you get a harmonic set up.

Damned if I can remember what it's even called -- or where I've read about it -- etc but it's there somewhere on the Internet. And it may be something Ron Sutton knows about - or someone else on here.

This??

http://www.chevyhardcore.com/tech-st...for-your-ride/

[GregWeld]

BINGO!!!

Originally Posted by Sieg

Thanks to Blake's mention of Mark Williams........

Critical speed is the speed at which a spinning shaft will become unstable. This is one of the single largest factors in driveshaft selection. When the whirling frequency and the natural frequency coincide, any vibrations will be multiplied. So much that the shaft may self destruct. Another way to think of this is that if a shaft naturally vibrates at 130 times a second, and one point on the shaft passes through 0 degrees 130 times a second (7800 RPM) then the shaft has hit a critical speed. There are several ways to raise the critical speed of a driveshaft. You can make it lighter, stiffer, or increase diameter without increasing weight. This is the reason carbon fiber makes a good driveshaft, it is stiff and light and can be made to any diameter or wall thickness. Aluminum, while it has a very good critical speed is not quite as strong as steel. Steel, with good strength characteristics will have a lower critical speed.