set pinion angle at -2 now vibration 80mph
11-10-2008, 09:35 AM
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set pinion angle at -2 now vibration 80mph hello everyone i recently installed my midwest 9" and couldn't be happier. problem is when i had my pinion angle at posative 1 i had no vibration that i can remember. however i had my friend adjust the pinion angle to negative 2 and yes he knows what he is doing, but now i have a vibration at around 80+ mph almost like the car is hopping up and down. anyone have this problem? its weird how i didn't have that problem with a posative angle though
11-10-2008, 10:25 AM
#3
Hello, when you set the pinion angle did you figure in the driveshaft angle also? Take a look at the video video on our site its explains the proper way to check the angle. It sounds like you have too much negative angle. If you have any questions please give me a call.
http://www.bmrtvonline.com/video_detail.php?mId=3788
http://www.bmrtvonline.com/video_detail.php?mId=3788
11-10-2008, 12:36 PM
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yes i did subtract the pinion from the driveshaft and lessening the pinion angle is not a correct way to fix a vibration issue due to the fact that factory is set at -2 and for drag racing you need to have a somewhat negative angle
11-10-2008, 02:07 PM
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You may -want- a -2 torque arm (pinion) angle but
you -need- a zero net driveline angle to minimize
the vibration.
To get both at once, you need either a bunch of
luck, or adjustability at both ends of the torque
arm. Like a relocating crossmember w/ adjustment
holes. Say hello to even more vibration.
You could try down-shimming the trans tail mount
from the floor pan and see if that picks you up
enough driveline angle to settle it down. Start
with measuring the resting driveline angle (as
difference between pinion angle and trans pan
angle, with the angle finder oriented the same
direction for both).
you -need- a zero net driveline angle to minimize
the vibration.
To get both at once, you need either a bunch of
luck, or adjustability at both ends of the torque
arm. Like a relocating crossmember w/ adjustment
holes. Say hello to even more vibration.
You could try down-shimming the trans tail mount
from the floor pan and see if that picks you up
enough driveline angle to settle it down. Start
with measuring the resting driveline angle (as
difference between pinion angle and trans pan
angle, with the angle finder oriented the same
direction for both).
11-10-2008, 04:40 PM
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i talked with eric from midwest he advised me to try adjusting the torque arm at the crossmemeber and readjusting the pinion and seeing what works well with the car
11-11-2008, 07:39 PM
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ok so i have an update the vibration almost moved up 10 or 20 mph instead of virbrating at 65 mph it now vibrates about 80 + at 110 mph it is terrible and shakes the entire car.
anyone ever experience this problem?
anyone ever experience this problem?
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11-12-2008, 04:43 AM
#8
Use the X dimension
Is your driveshaft the correct length? I have seen vibrations caused by the driveshaft being too short. Bob
11-12-2008, 08:05 AM
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i am not sure if it is the same lenght because i never had one to measure up to in the first place. anyone know what lenght it should be? i have a 9" by the way
11-12-2008, 08:16 AM
#10
Most 9 inch rears really need a one inch longer driveshaft to get them back to the correct length. We have had a few that vibrated without going to the longer driveshaft. Bob
11-12-2008, 10:51 AM
#11
driveshaft center to center length will be affected by the trans yoke you are using. chances are if you were to use the yoke that SLP Firehawk has on his driveshaft it would make the 1" longer spec bottom out in the trans. the length of the spline area and the center of the u-joint to end of the splines in the yoke are not always the same and this changes the actual u-joint center to center length of the driveshaft. the nine inch ford bolt-in rearends i sell are about 1/4 inch shorter in pinion length than the stock 10 bolt. the Strange 3 inch Chromemoly driveshaft that most everybody with this rearend has purchased is set at 41 5/8 center to center. wheelbase adjustment can affect the length of the driveshaft as well, so be sure that the rearend is set correctly within the car. chances are is it is a pinion angle issue.
