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Our LS400 driveshaft incorporates a single center u-joint...and there is no second u-joint to counteract u-joint induced oscillation, suggesting driveshaft rubber guibos serve this purpose.
While our u-joint angles are not as far ranging as with a solid axle rear differentiall, use of constant velocity joints in place of driveshaft u-joints in contemporary vehicles suggests improve smoothness.
(If anyone has images please share).
Constant velocity joint are more expensive than u-joints....
Why a single u-joint in a driveshaft is a bad idea:
Drive Shaft Harmonics Driveline/Universal Joint Cancellation By: Jim Clark, Hot Rod M.D.
What: Solving the problem of driveline vibration. Driveline geometry. The process that can be used to address a condition called driveline/universal joint cancellation, often referred to as adjusting pinion angle. This process can be used to eliminate the vibration and premature wear caused by improper orientation and phasing of the driveline.
This condition is caused because every U-joint that operates at an angle creates a vibration. It creates that vibration because the U-joint cross rotates with the shaft in a circular motion while also moving from front to rear. That rocking back and forth motion as it rotates causes the cross in the U-joint to accelerate and decelerate.
If you could view this as rotating around the face of a clock with the cross rotating in a counterclockwise motion it would show the U-joint when at a horizontal position (3 to 9 o’clock) as traveling in a circular motion. As the yoke arm at 3 o’clock travels counterclockwise towards 12 o’clock and tips to the rear of the vehicle it accelerates. Then decelerates as it continues counterclockwise towards 9 o’clock as it rocks forward again returning to center. Now again accelerates as it continues rotating counterclockwise from 9 o’clock to 6 o’clock and rocking towards the front of the vehicle. Finally completing one rotation as it travels counterclockwise from 6 o’clock to 3 o’clock decelerating as it returns to center. Because the U-joint is connected to the driveshaft and accelerates/decelerates through this full rotation, the driveshaft speeds up and slows down during each revolution. This creates what is called excitation torque.
When viewed from the end, the path taken by the bearing cups is an ellipse, rotating forward and backwards as well as in its path around the centerline of the shaft. When viewed from the side, the path taken by the bearing cups would look like an angled line rocking back and forth while rotating around the centerline of the shaft
To cancel this excitation torque, the U-joint at the other end of the shaft needs to rotate at an equal but opposite angle in relation to the U-joint up front. By using U-joints in pairs and in phase, and the angle between the driveshaft and the equipment at both ends is the same, the acceleration/deceleration cycles tend to cancel each other.
These U-joint angles should always be at least 1-degree to avoid wearing out the yoke bearings.
How: When you build a chassis and position the driveline components, you need to orient them so that the angle of a line drawn through the center of the transmission exiting through the output shaft (A) and a line drawn through the center of the driveshaft (B) is equal to but opposite the angle of a line drawn through the pinion shaft in the rear differential(C) and the line drawn through the center of the driveshaft (B). The accompanying drawing illustrates how the lines drawn through the transmission and pinion shafts (A&C) are parallel to each other, though not in the same plane.
This drawing illustrates the relationship that needs to be established between the three main driveline components.
U-joint operating angles are generally the most common cause of driveline vibration in vehicles that have been reworked. When reworking a chassis or installing a new driveshaft in a vehicle there are basic rules that apply to U-joint operating angles that you should follow.
Number-1: U-joint operating angles at each end of the shaft should always be at least 1-degree.
Number-2: If you are to achieve cancellation these U-joint operating angles on each end of a driveshaft should always be equal (within 1-degree), but opposite of each other.
Number-3: U-joint operating angles should not be larger than 3-degrees. If they are, make sure that they do not exceed the maximum recommended angles.
To set up the driveline you need to establish the angles for the transmission output shaft, rear end pinion shaft and driveshaft. A good tool for measuring these angles is an inclinometer. They can be obtained quite inexpensively from a local parts store or tool supplier.
First measure the transmission output shaft angle. It should be pointing downward to the rear with the vehicle sitting at ride height on a level surface. At least 1-degree and ideally not more than 3-degrees down. You can alter the transmission angle by inserting or removing shims under the rear transmission mount as shown in this photo.
Next step is to measure the rear end pinion shaft angle. It should be pointing upward towards the front with the vehicle sitting at ride height on a level surface. At least 1-degree and ideally not more than 3-degrees up. You can alter the rear end pinion shaft angle by inserting or removing wedge shaped shims under the rear spring mounts or by adjusting the length of the control arms positioning the rear end. See photo below.
Finally measure the driveshaft angle to confirm that it is at least 1-degree down from the transmission output shaft angle and at least 1-degree up from the rear end pinion shaft angle. Achieving these angles in relation to each other will cancel out the vibration.
Checking to see if you have got it correct: If there is no vibration under normal operating conditions then the angles are correct.
If there is vibration under acceleration, you need to add more downward pinion angle preload. If the opposite occurs, the vibrations tends to decrease or disappear under acceleration, you need to reduce the downward angle preload.
If the vibration steadily increases with driveshaft speed (either accelerating or decelerating) the symptom is primarily the result of a driveshaft imbalance or yoke runout. Sometimes this yoke runout problem can be improved by rotating the U-joint 180-degrees in the rear end differential yoke.
Driveshaft-related vibrations usually occur at roughly engine speed in high gear. Wheel/axle vibrations usually occur at 1/3 rd engine speed or driveshaft speed because of the differential gearing. To determining whether it is the output of the transmission or the pinion in the differential, change gears when the noise occurs and maintain speed. If the vibration/noise changes in frequency, the source is in the transmission or engine. If the frequency remains the same it is a driveline problem.
When I swapped my 275k higher mileage driveshaft out for a 95k lower mileage one, I noticed that the center carrier bearing was encompassed in a rubber bushing to aid in dampening of NVH, it was flexible slightly and not completely rigid. But I mainly did the swap since both of my guibo bushing were cracked all the way to the bolts and was worried they would break eventually. In case anyone is wondering, I paid $55 for my double driveshaft is what the Pick N Save called it. Still have my old one if anyone needs anything from it.
@Losiracer2
So you didn't have any vibrations/noise prior to your driveshaft swap? I take it then it was a preventative maintenance issue then?
yeah, I was moving to Ann Arbor Michigan from AZ, about 2000 miles from home and everything familiar to me for a new job and didn't want to take a chance for those guibo joints failing. Not to mention, there aren't any LS400s within a 100 mile radius from me in JYs here since this is the rust belt. So I didn't want to get raped paying a shop labor to remove the driveshaft and have to buy aftermarket guibos and risk having to do the job again in a couple years due to subpar rubber.
i would like to do the trans mount and also replace this joint..i have over 200k and its all original..im experiencing a slight vibration through the gear shift handle and at speeds over 90 mph.
When I swapped my 275k higher mileage driveshaft out for a 95k lower mileage one, I noticed that the center carrier bearing was encompassed in a rubber bushing to aid in dampening of NVH, it was flexible slightly and not completely rigid. But I mainly did the swap since both of my guibo bushing were cracked all the way to the bolts and was worried they would break eventually. In case anyone is wondering, I paid $55 for my double driveshaft is what the Pick N Save called it. Still have my old one if anyone needs anything from it.
2) Unbeknownst to most driveshaft shops, Lexus does final balancing with different weight guibo bolts between the driveshaft flange and guibo disk. That is why they plead that you only detach driveshaft from car using the guibo-to-transmission flange or guibo-to-differential flange. Weigh your friggen bolts anyway if the drive shaft has ever been removed or your guibo disks ever replaced.
So, I had a question for you Losiracer. Did you manage to get the driveshaft off the transmission without fully removing the exhaust up there, or do you have to remove the exhaust?
Colin
[h3]Our LS400 driveshaft incorporates a single center u-joint...and there is no second u-joint to counteract u-joint induced oscillation, suggesting driveshaft rubber guibos serve this purpose.
Lexus side-stepped this problem by demanding a "0" deviation through the entire driveshaft. All flanges are supposed to be exactly the same angle. The driveshaft has to be dead straight through all components. Therefore there is no movement of the yokes in normal driving. The only function of the center u-joint is to handle transient flexing. The guibo disks are merely axial shock absorbers and hate any call to act like a u-joint.
IF there was any need to run an angle through the driveshaft (like half shafts often have to) then constant velocity joints are the only way to go. Old American cars had to run angles with live rear axles and the u-joints themselves required a 1/2 to 1* angle through each joint to exercise the needles so they wouldn't wear flat and to keep the needles from wearing dents into the races.
Colin
Lexus side-stepped this problem by demanding a "0" deviation through the entire driveshaft. All flanges are supposed to be exactly the same angle. The driveshaft has to be dead straight through all components. Therefore there is no movement of the yokes in normal driving. The only function of the center u-joint is to handle transient flexing. The guibo disks are merely axial shock absorbers and hate any call to act like a u-joint.
IF there was any need to run an angle through the driveshaft (like half shafts often have to) then constant velocity joints are the only way to go. Old American cars had to run angles with live rear axles and the u-joints themselves required a 1/2 to 1* angle through each joint to exercise the needles so they wouldn't wear flat and to keep the needles from wearing dents into the races.
Colin
Makes the case for refreshing engine and transmission mounts, center bearing support and differential bushings to maintain 0 deviation...
Plausibly 20 -30 year old rubber guibos are not as effective isolating vibration or maintaining accurate phasing.(between front and rear flange sets)
The shop manual has an entire section on topic but not recalling perfect 0 driveshaft angle.
Single u-joints reminds me of the Chevrolet Corvair that used only one u-joint in each half shaft (!).
CV joints are more expensive than u joints which in part explains their application.
Contemporary rear wheel drive luxury sedans with independent rear suspensions favor cv joint(s) over u joints in primary driveshaft.
Lexus side-stepped this problem by demanding a "0" deviation through the entire driveshaft. All flanges are supposed to be exactly the same angle. The driveshaft has to be dead straight through all components. Therefore there is no movement of the yokes in normal driving. The only function of the center u-joint is to handle transient flexing. The guibo disks are merely axial shock absorbers and hate any call to act like a u-joint.
IF there was any need to run an angle through the driveshaft (like half shafts often have to) then constant velocity joints are the only way to go. Old American cars had to run angles with live rear axles and the u-joints themselves required a 1/2 to 1* angle through each joint to exercise the needles so they wouldn't wear flat and to keep the needles from wearing dents into the races.
Colin
Wow, great info. I noticed in the quoted article above, it seemed to say the angles had to be between 1 and 3 degrees. So I wondered about why it was 1 degree minimum. Your second paragraph here answers that, right?
2) Unbeknownst to most driveshaft shops, Lexus does final balancing with different weight guibo bolts between the driveshaft flange and guibo disk. That is why they plead that you only detach driveshaft from car using the guibo-to-transmission flange or guibo-to-differential flange. Weigh your friggen bolts anyway if the drive shaft has ever been removed or your guibo disks ever replaced.
So, I had a question for you Losiracer. Did you manage to get the driveshaft off the transmission without fully removing the exhaust up there, or do you have to remove the exhaust?
Colin
Yep, the car I removed it from, a 97' Coach Edition w/ 95k miles, was in the JY and had everything still on it. I left the exhaust intact and just removed a few braces from what I remember 2 years ago. I took me about 45 min to remove from the car in the JY with basic hand tools. The car was also a Minnesota car which seemed to have no rust, so most likely a snowbird car in AZ for winters.
Yep, the car I removed it from, a 97' Coach Edition w/ 95k miles, was in the JY and had everything still on it. I left the exhaust intact and just removed a few braces.
I hope a 1991 is not different in any appreciable way from your '97. I really do hope.
Colin
11-23-18, 09:39 PM
Ls400 drivetrain u-joint induced oscillations
