interesting video (drive shaft alignment)

[Kevin Mac]

This was sent to me and thought I would share it.
https://www.facebook.com/ScottTuning...saNs_JDtQ1kouk

Mac

[mr48chev]

That is a good one that does the job of explaining things. Wish I had had access to that when I was teaching my shop students about drivetrains.

We had a a guy bring an early 60's Chevy car into the high school shop while I was teaching that had a vibration that no one could figure out. If you know those cars you know they have what we used to call a sling shot frame where the rails narrow to the middle and the driveshaft runs right down the middle, We checked wheel balance with the Hunter on car balancer and it was real close to begin with, we raised it up on the hoist an started looking and started looking at the driveshaft. When we rotate the shaft so the front U joint was square with the floor if you will we looked at the rear U joint and it was off a bit from the front. We pulled the shaft and set it on the bench and sure enough who ever had replaced the center support had put the yoke on out of phase with the front joint. A 30 minute fix and no more vibration. Best part was even though I could see what was wrong the kids figured it out on their own. Several of that bunch are hard core car and truck guys in their 50's now.

[hewittca]

That's the same video I watched when trying to figure out a vibration in my drive shaft. In fact, after watching it I was talking to someone who is very knowledgeable about automotive repair in general but was giving me information that did not jive with what I heard in this video. He ended up helping me set the angles as he described and it was better but not perfect. Despite my trust in this persons opinion, I decided on my own to reset my driveshaft angles in the manner described by the video and the result was no more driveshaft vibration!

[MARTINSR]

Originally Posted by hewittca

That's the same video I watched when trying to figure out a vibration in my drive shaft. In fact, after watching it I was talking to someone who is very knowledgeable about automotive repair in general but was giving me information that did not jive with what I heard in this video. He ended up helping me set the angles as he described and it was better but not perfect. Despite my trust in this persons opinion, I decided on my own to reset my driveshaft angles in the manner described by the video and the result was no more driveshaft vibration!

Good stuff there! Yep, get advice from many people and think it out.

Brian

[mongocanfly]

that's a good video..I know its been linked to a lot of driveline questions on here before...

[Advanced Design]

Originally Posted by mr48chev

That is a good one that does the job of explaining things. Wish I had had access to that when I was teaching my shop students about drivetrains.

We had a a guy bring an early 60's Chevy car into the high school shop while I was teaching that had a vibration that no one could figure out. If you know those cars you know they have what we used to call a sling shot frame where the rails narrow to the middle and the driveshaft runs right down the middle, We checked wheel balance with the Hunter on car balancer and it was real close to begin with, we raised it up on the hoist an started looking and started looking at the driveshaft. When we rotate the shaft so the front U joint was square with the floor if you will we looked at the rear U joint and it was off a bit from the front. We pulled the shaft and set it on the bench and sure enough who ever had replaced the center support had put the yoke on out of phase with the front joint. A 30 minute fix and no more vibration. Best part was even though I could see what was wrong the kids figured it out on their own. Several of that bunch are hard core car and truck guys in their 50's now.

Great story about the learning process! Probably one they never forgot.

I remember studying how a differential worked when in automotive college in 1979 using a text book with description and text. While I eventually grasped it, a video readily available on YouTube today would have helped augment the learning.

That is a good video explaining why U-joints are needed. Of course, working angles and phasing are only one potential contributor to driveline vibration. Drive shaft run out, balance, and even a bent pinion gear can contribute too.

[Keith Seymore]

Originally Posted by Advanced Design

That is a good video explaining why U-joints are needed. Of course, working angles and phasing are only one potential contributor to driveline vibration. Drive shaft run out, balance, and even a bent pinion gear can contribute too.

True: except run out, imbalance and bent pinion would all be a "first order of rotation" disturbance (one "kick" per rev).

The angle and phasing issues being discussed here are "second order of rotation" disturbances (two "kicks" per rev).

Different root cause and vibration "signature" even though they all ride on the same components.

Originally Posted by Advanced Design

I remember studying how a differential worked when in automotive college in 1979 using a text book with description and text. While I eventually grasped it, a video readily available on YouTube today would have helped augment the learning.

One of my favorite memories is of watching my 8 year old son explain to his grandfather how a differential works, having created one out of Lego's for use as a visual aid -



K

[Advanced Design]

Originally Posted by Keith Seymore

True: except run out, imbalance and bent pinion would all be a "first order of rotation" disturbance (one "kick" per rev).

The angle and phasing issues being discussed here are "second order of rotation" disturbances (two "kicks" per rev).

Different root cause and result even though they all ride on the same components.



One of my favorite memories is of watching my 8 year old son explain to his grandfather how a differential works, by using Lego's as a visual aid -



K

Yes, and a shaft with a failed trunnion...fwd vehicle...can experience a third order wheel and tire speed vibration with three imbalances per rotation. Of course most folks don't have an EVA, Pico scope or a Reed tach to be able to measure for the orders of vibration.

The bent pinion showed as a first order prop shaft only under accel or decel.
Backlash variance helped confirm that one.

Having an 8 year old explain a differential operation with Lego would have been outstanding!

[mongocanfly]

"Having an 8 year old explain a differential operation with Lego would have been outstanding"

would have made a great video!!!