MTCFORUM
02-13-2002, 09:22 PM
Now to the meat.
Basically the driveline vibration can come down to a few subsystems, the wheels and tires, the driveshaft, the trans or the axle. There are few extreme cases that have torque converters that are out of balance, but these are rare. I'll cover each one seperatly and then tie them all together.
Wheel and Tires.
Since these chassis's are very sensitive to vibration input the wheels and tires must be balanced very, very well. This is pretty basic, I don't need to go over what to do, just get them balanced. A wheel vibration usually comes in slow, has a peak amplitude and then goes away or gets much better. If it's a front wheel you'll feel it/see it in the steering wheel. If it's a rear wheel, you'll feel it coming from the corner of the car that has the issue. I'll tell you how sensitive these chassis are to tires. The Mark 8 was supposed to have Goodyear tires at the start of production. All the preproduction cars had Goodyears. When Wixom starting making cars the cars has more vibration than normal and it was traced to tires. Do you what brand the cars were made with, Michillen (I can't spell really well, it's the sign of an engineer). To throw away all those Goodyears cost a lot of money, that's how important it was.
Transmission
The output shaft on the transmission appears straight. It also must be capable of handling alot of torque. For example, let's say a Mark 8 motor makes 250 ft-lbs at a full brake stall. The torque converter has a 2.40 stall multiplacation and low gear in the trans is 2.83999. So, the output shaft could see 250*2.40*2.83999 or 1704 ft-lbs. Now, you can probably add 10-15% for good cold weather.
So, to get a shaft to handle that much torque, and remember, at it's narrowest point it's only about 1.25" in diameter, you have to do one of two things. You either need really good material or you need to make it really hard. Initially, until 1997, the shaft was made from a 1020 steel that was carborized and then DOUBLE induction hardend. Now, if you know anything about metals, you know when you induction harden a shaft, it warps and twists. So, after the shaft is made from the raw materials, it's turned to rough finish surfaces. Then it's caborized and double induction hardend. This turns the shaft to a pretzel. It is then put into a huge press and is beaten back straight, I am very serious here. Then the shaft was put into a centerless grinder and finished. There are a few issues with this. You turn all the bearing surfaces in a lathe, and then finish grind it on a grinder that does not hold it to spin on the same centerline that it did when you initially turned it. Bottom line, you end up with the very likelyhood of two centers on the shaft. Then after it's beat back into shape, it may be straight on a macro level, but if you look at it more closely, you'll see that there a bunch of little ups and downs all the way down it.
So, what's all this mean? The shaft is not straight, has no center and can make a vehicle that has a sensitive chassis have vibration.
In 1997ish, they improved the material of the shaft to 1045 steel. This results in a stronger shaft with little induction hardening so it is alot straighter. You can see this shaft by it's color.
There is also a ring gear in the transmission that the output shaft splines to. It's about 6-7" in diameter and can also be out of balance. I'll touch on this a little later when I get to the whole system.
Axle
The axle itself can only affect driveline vibration in a few ways. Picture the pinion spinning with the companion flange attached. The companion flange is a round flange that splines/bolts to the pinion gear and has 8 threaded holes that the driveshaft bolts to.
The vibration here can come from the center of the pinion and companion flange, not spinning in a true centerline. It can turn in an ellipse. Again this can set off vibration in a vehicle with a sensitive chassis.
Driveshaft
The driveshaft has a few things that affect the vibration. The first is obvious, the shaft needs to be balanced well. The second is the straightness of the shaft or runnout. If you spin the shaft on it's centerline how true is the outside of the shaft spinning? This is similar to the runout of the pinion and companion flange.
I don't know if the board would let me write one massive post so I'm doing this in 3 parts. This is the finish of the 2nd part.
jerry
Basically the driveline vibration can come down to a few subsystems, the wheels and tires, the driveshaft, the trans or the axle. There are few extreme cases that have torque converters that are out of balance, but these are rare. I'll cover each one seperatly and then tie them all together.
Wheel and Tires.
Since these chassis's are very sensitive to vibration input the wheels and tires must be balanced very, very well. This is pretty basic, I don't need to go over what to do, just get them balanced. A wheel vibration usually comes in slow, has a peak amplitude and then goes away or gets much better. If it's a front wheel you'll feel it/see it in the steering wheel. If it's a rear wheel, you'll feel it coming from the corner of the car that has the issue. I'll tell you how sensitive these chassis are to tires. The Mark 8 was supposed to have Goodyear tires at the start of production. All the preproduction cars had Goodyears. When Wixom starting making cars the cars has more vibration than normal and it was traced to tires. Do you what brand the cars were made with, Michillen (I can't spell really well, it's the sign of an engineer). To throw away all those Goodyears cost a lot of money, that's how important it was.
Transmission
The output shaft on the transmission appears straight. It also must be capable of handling alot of torque. For example, let's say a Mark 8 motor makes 250 ft-lbs at a full brake stall. The torque converter has a 2.40 stall multiplacation and low gear in the trans is 2.83999. So, the output shaft could see 250*2.40*2.83999 or 1704 ft-lbs. Now, you can probably add 10-15% for good cold weather.
So, to get a shaft to handle that much torque, and remember, at it's narrowest point it's only about 1.25" in diameter, you have to do one of two things. You either need really good material or you need to make it really hard. Initially, until 1997, the shaft was made from a 1020 steel that was carborized and then DOUBLE induction hardend. Now, if you know anything about metals, you know when you induction harden a shaft, it warps and twists. So, after the shaft is made from the raw materials, it's turned to rough finish surfaces. Then it's caborized and double induction hardend. This turns the shaft to a pretzel. It is then put into a huge press and is beaten back straight, I am very serious here. Then the shaft was put into a centerless grinder and finished. There are a few issues with this. You turn all the bearing surfaces in a lathe, and then finish grind it on a grinder that does not hold it to spin on the same centerline that it did when you initially turned it. Bottom line, you end up with the very likelyhood of two centers on the shaft. Then after it's beat back into shape, it may be straight on a macro level, but if you look at it more closely, you'll see that there a bunch of little ups and downs all the way down it.
So, what's all this mean? The shaft is not straight, has no center and can make a vehicle that has a sensitive chassis have vibration.
In 1997ish, they improved the material of the shaft to 1045 steel. This results in a stronger shaft with little induction hardening so it is alot straighter. You can see this shaft by it's color.
There is also a ring gear in the transmission that the output shaft splines to. It's about 6-7" in diameter and can also be out of balance. I'll touch on this a little later when I get to the whole system.
Axle
The axle itself can only affect driveline vibration in a few ways. Picture the pinion spinning with the companion flange attached. The companion flange is a round flange that splines/bolts to the pinion gear and has 8 threaded holes that the driveshaft bolts to.
The vibration here can come from the center of the pinion and companion flange, not spinning in a true centerline. It can turn in an ellipse. Again this can set off vibration in a vehicle with a sensitive chassis.
Driveshaft
The driveshaft has a few things that affect the vibration. The first is obvious, the shaft needs to be balanced well. The second is the straightness of the shaft or runnout. If you spin the shaft on it's centerline how true is the outside of the shaft spinning? This is similar to the runout of the pinion and companion flange.
I don't know if the board would let me write one massive post so I'm doing this in 3 parts. This is the finish of the 2nd part.
jerry