Is this the source of many of our driveline vibrations?
01-14-2010, 11:56 PM
#1
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Join Date: May 2001
Location: Utah
Posts: 127
Have driveshaft vibrations? Look in here....
I've searched this forum to no end, and there are countless threads about driveshaft vibrations - most are caused after rear end installs, torque arm installs, or transmission mount installs.... not many have been successful in resolving their vibration issues, but I think we're doing it wrong?
I just surfed on to this article:
http://buickperformance.com/Pinion.htm
The summary is that the pinion yoke should be 100% parallel to the output shaft of the transmission (to have true 0* pinion angle, but obviously you actually want the rear end pointed down 1 - 2 degrees), and that driveshaft angle vs pinion yoke angle doesn't matter.
I've always setup my cars (had a '94 and now a '97) as pinion yoke vs driveshaft angle - but if the transmission and pinion yoke arent parallel, it doesnt matter, you'll get vibration.
I'll bet money this is the source of my driveshaft vibration (and many others), that is especially noticeable after 65+ and on deceleration. Hopefully I havent ruined my u-joints.
I'm betting as our cars get older, we start to change the geometry of the transmission output shaft and pinion yoke due to sagging motor mounts, sagging springs / lowered cars, and installed after market torque arms etc
I'll give this a shot tomorrow, but I'm betting Im off by at least 6* or more.
Thoughts?
I just surfed on to this article:
http://buickperformance.com/Pinion.htm
The summary is that the pinion yoke should be 100% parallel to the output shaft of the transmission (to have true 0* pinion angle, but obviously you actually want the rear end pointed down 1 - 2 degrees), and that driveshaft angle vs pinion yoke angle doesn't matter.
I've always setup my cars (had a '94 and now a '97) as pinion yoke vs driveshaft angle - but if the transmission and pinion yoke arent parallel, it doesnt matter, you'll get vibration.
I'll bet money this is the source of my driveshaft vibration (and many others), that is especially noticeable after 65+ and on deceleration. Hopefully I havent ruined my u-joints.
I'm betting as our cars get older, we start to change the geometry of the transmission output shaft and pinion yoke due to sagging motor mounts, sagging springs / lowered cars, and installed after market torque arms etc
I'll give this a shot tomorrow, but I'm betting Im off by at least 6* or more.
Thoughts?
Last edited by NVMYZ28; 01-15-2010 at 10:05 PM.
01-15-2010, 12:04 AM
#2
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Join Date: May 2001
Location: Utah
Posts: 127
Man, the more I think about this the more it makes sense!
If you have the front U-Joint with an angle on it, while the rear U-join is perfectly straight (you would get this scenario if the rear end and transmission are not parallel) things are going to vibrate! But if both U-joints have the same angle on them, they will rotate in harmony.
I'm POSITIVE this is the source of my drive train vibration - cant wait to resolve it tomorrow.
If you have the front U-Joint with an angle on it, while the rear U-join is perfectly straight (you would get this scenario if the rear end and transmission are not parallel) things are going to vibrate! But if both U-joints have the same angle on them, they will rotate in harmony.
I'm POSITIVE this is the source of my drive train vibration - cant wait to resolve it tomorrow.
01-15-2010, 09:17 PM
#3
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Join Date: May 2001
Location: Utah
Posts: 127
FIXED!!!!!
So I went to sears today and bought a digital angle finder, and made the adjustments (this angle finder is good to 0.1 degrees accuracy)
To start, I tried to figure out the best place to measure the angle of the output shaft of the transmission.... my Y-Pipe is right in the way of any chance of getting my new angle finder vertically against the end of the tail shaft housing, and I didnt want to remove my exhaust. So, I found that the mounting point for the clutch slave cylinder would work as its parallel to the output shaft tail housing.
I removed the clutch slave cylinder and is aluminum spacer/bracket, and then removed the drive shaft from the rear end yoke. (I left it plugged in to the trans).
Here are the angles I found (car was not 100% level, but pretty close):
Lets say this is the Front of the Car: | engine slope: / and this is the rear end yoke slope: \
Transmission: / 86.3* Rear End: \ 88.9* (90* being perfectly vertical).
Thats a net difference between the rear end and transmission output shaft of 4.8 degrees!!!!!
I sucked the torque arm adjusting nut in a bunch, swinging the rear up quite a bit, and now I only have a net diff of 1.7 degrees.
Put everything back together, took it for a spin up to 90.... and the vibration is 98% GONE. I'll bet if push the yoke up just a touch more, this thing will be 100% smooth as silk.
I'm glad I can put this one to bed! This plagued me in my '94 (enough that I sold the spohn torque arm), and now has plagued me in my '97, but its finally FIXED!
Hopefully this helps someone else sometime....
P.S. If any of you after market torque arm manufacturers read this - please add a note to your instructions to indicate that pinion angle should be set relative to transmission output shaft, and not the drive shaft. Drive shaft angle is irrelevant if the pinion angle and transmission output shaft angles are significantly off.
So I went to sears today and bought a digital angle finder, and made the adjustments (this angle finder is good to 0.1 degrees accuracy)
To start, I tried to figure out the best place to measure the angle of the output shaft of the transmission.... my Y-Pipe is right in the way of any chance of getting my new angle finder vertically against the end of the tail shaft housing, and I didnt want to remove my exhaust. So, I found that the mounting point for the clutch slave cylinder would work as its parallel to the output shaft tail housing.
I removed the clutch slave cylinder and is aluminum spacer/bracket, and then removed the drive shaft from the rear end yoke. (I left it plugged in to the trans).
Here are the angles I found (car was not 100% level, but pretty close):
Lets say this is the Front of the Car: | engine slope: / and this is the rear end yoke slope: \
Transmission: / 86.3* Rear End: \ 88.9* (90* being perfectly vertical).
Thats a net difference between the rear end and transmission output shaft of 4.8 degrees!!!!!
I sucked the torque arm adjusting nut in a bunch, swinging the rear up quite a bit, and now I only have a net diff of 1.7 degrees.
Put everything back together, took it for a spin up to 90.... and the vibration is 98% GONE. I'll bet if push the yoke up just a touch more, this thing will be 100% smooth as silk.
I'm glad I can put this one to bed! This plagued me in my '94 (enough that I sold the spohn torque arm), and now has plagued me in my '97, but its finally FIXED!
Hopefully this helps someone else sometime....
P.S. If any of you after market torque arm manufacturers read this - please add a note to your instructions to indicate that pinion angle should be set relative to transmission output shaft, and not the drive shaft. Drive shaft angle is irrelevant if the pinion angle and transmission output shaft angles are significantly off.
Last edited by NVMYZ28; 01-15-2010 at 09:25 PM.
01-19-2010, 07:44 PM
#4
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Join Date: May 2005
Location: Colorado
Posts: 2,161
yup, Im guessing this is my problem too. I put in a strange dana 60 and chrome moly driveshaft, and have had a vibration ever sense. Over this winter I have been talking to a NHRA drag racer I work with, and he told me to make sure the output shaft on the tranny matches my rear. Problem was, when I looked, I couldn't get a clear spot to put the angle finder on my tranny. Thanks to this thread, I have a place to start. 
AWESOME!!!!! This vibration has pissed me off for over a year!
AWESOME!!!!! This vibration has pissed me off for over a year!
03-29-2010, 10:57 PM
#7
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Join Date: May 2005
Location: Colorado
Posts: 2,161
Im doing a clutch install, and since I had the y pipe off I measured my angels for sh*ts and giggles.
The engine slopes like this \ and it reads positve 5 degrees. The tranny sits like this / at negative .5 degrees. 5.5 difference! I cant wait to get my pinion lined up with the tranny and see what happens. Im hoping that this makes my vibration go away since installing the dana 60. Will keep updated when it is back together with the mcleod street twin and I can drive it.
The engine slopes like this \ and it reads positve 5 degrees. The tranny sits like this / at negative .5 degrees. 5.5 difference! I cant wait to get my pinion lined up with the tranny and see what happens. Im hoping that this makes my vibration go away since installing the dana 60. Will keep updated when it is back together with the mcleod street twin and I can drive it.
03-30-2010, 04:21 PM
#8
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Join Date: May 2001
Location: Utah
Posts: 127
Ideally the place you want to measure is on the output shaft of the transmission - but with y/pipes etc in the way its not convenient.
I had no idea there was that much difference between the damper and the transmission, i wonder if the spot I measured mine (the slave cylinder mount on the transmission) matches the output shaft. My vibration is substantially better, but with the solid mount spohn torque arm, every bit I can eliminate, the better
I had no idea there was that much difference between the damper and the transmission, i wonder if the spot I measured mine (the slave cylinder mount on the transmission) matches the output shaft. My vibration is substantially better, but with the solid mount spohn torque arm, every bit I can eliminate, the better
03-30-2010, 05:45 PM
#9
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Join Date: May 2005
Location: Colorado
Posts: 2,161
Ideally the place you want to measure is on the output shaft of the transmission - but with y/pipes etc in the way its not convenient.
I had no idea there was that much difference between the damper and the transmission, i wonder if the spot I measured mine (the slave cylinder mount on the transmission) matches the output shaft. My vibration is substantially better, but with the solid mount spohn torque arm, every bit I can eliminate, the better
I had no idea there was that much difference between the damper and the transmission, i wonder if the spot I measured mine (the slave cylinder mount on the transmission) matches the output shaft. My vibration is substantially better, but with the solid mount spohn torque arm, every bit I can eliminate, the better
03-31-2010, 01:44 PM
#11
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Join Date: May 2005
Location: Colorado
Posts: 2,161
I dont know about your setup, but mine is a bitch to get apart. I thought I was doing good to make the pipes fit inside each other all the way, so no slack to pull just a piece out. DUMB! haha.
04-03-2010, 02:50 PM
#13
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Join Date: May 2001
Location: Dover, Ohio
Posts: 69
Crazy how I just found this thread because I just fixed my vibration issue this morning by do the same exact thing listed by the OP. However, I got the idea from an article in Hot Rod Magazine.
When I checked mine, it was out by about 6 degrees and it has been like that for about 3 years! I can't believe it was such a simple fix. In the past, I had messed with the pinion angle, but I never measured as mentioned in this thread.
When I checked mine, it was out by about 6 degrees and it has been like that for about 3 years! I can't believe it was such a simple fix. In the past, I had messed with the pinion angle, but I never measured as mentioned in this thread.
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