Yoke phasing

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73Scamp318

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I have a quick question about yoke phasing, but first some background...

I've been chasing an oscillating vibration on my car since I assembled it that starts in gently at around 2500 in high gear and gets progressively more intense the higher up in RPMs I go. I only feel it when I'm cruising along on the highway and it'll rattle your teeth at 4000. If I'm running WOT, either it's lessened or I just don't notice it because I'm busy.

I recently took the shaft into a local driveline shop to have it checked and get the U-joints replaced and I noticed the yokes on the shaft are visibly not aligned. Not severe...maybe around 5 to 10 degrees, but enough to notice just eyeballing it. I asked them about it when I dropped it off and told them about my issue, they told me "don't worry about it".

Well, the shaft is back in the car with fresh joints and the vibration is exactly the same as it was before. I've tried changing the pinion angle and added/removed shims under the trans mount with no effect on the vibration.

Could the yokes be the issue? My engine/trans mounts are only a couple of years old and, eyeballing from the rear, it looks like the pinion is in line with the transmission. I could try swapping the center section or borrowing a set of tires, but I've been through the tires before with no luck.

Thanks for any assistance.
 
Are you referring to the two yokes on the shaft itself? Yes they are suppose to be in line. If they aren't than whom ever built the shaft screwed up.
 
These MUST be in alignment. I'm not sure "at what point" it becomes significant, but 10 degrees is a hell of a lot.

Example:

Used to have a Jeep transfer in my old Landcruiser, using Bronco shafts so the slip yoke (spline) was on the shaft

One cold sloppy winter day I had a bad joint, and managed to get under, get the slip yoke off the shaft and change the joint in "record time." But somehow I got the yoke "unclocked" one spline. I just could not believe how bad that thing shook at about 40 mph.

This was probably worse than your car, because it was a short shaft and a fairly steep angle (front shaft)

Also, not having these properly clocked indicates just plain sloppy work by the shop. If they can't properly align shaft yokes, makes ya wonder how good (balance) the rest of it is
 
Have you measured the angle between the pinion axis and ground and the transmission axis and ground? They need to be about the same angle (reversed) or the pinion can be up to a max of 4 degrees closer to the ground so that under full load, it rotates up to the same inverse angle as the transmission.

If you've done this measurement and they're good, then start worrying about syncing the universals, but yes they should be identical.
 
SGBARRACUDA said:
Absolutely, Did this same shop do the driveshaft?
Click to expand...

Not sure if they built this particular shaft, it's one that my dad had in his shop that had been collecting dust for quite some time. I have no idea how old it is or who built it, but it does look like a shortened shaft.

I have checked the angles of the trans output and pinion. I've tried them equal, pinion -2 and -4, with no changes.

I will normally try to find a local place to give money to for this kind of thing, but am giving serious consideration to mail order. I was thinking about getting a new driveshaft, but I'm not sure if I want to let the same outfit take a swing at making a new shaft.
 
Why not grind the welds down on the yokes, realign them and reweld them? You only need to do this to one end. Remember that the shaft is hollow and the yoke is just welded around the tube's circumference. Then you can have a driveshaft shop rebalance it if it shimmies. This would be the cheapest way to test the guess.
 
If I had more confidence in the welder I have access to and my abilities, I would give that a shot.

The cheap way for me that I would be comfortable with is to have a driveshaft shop do the cut, reposition, and reweld.

I'll have to see if I can round up an angle finder again and check how far out the yokes really are.
 
Don't do as instructed, just find a REAL driveline shop.

Take the shaft and level off one weld yoke and then measure the other side, 5 degrees or more can make a issue as the shaft speed increases as you see
 
Supershafts said:
Don't do as instructed, just find a REAL driveline shop.

Take the shaft and level off one weld yoke and then measure the other side, 5 degrees or more can make a issue as the shaft speed increases as you see
Click to expand...
x2 or just buy one of his..............Artie
 
73Scamp318 said:
I have a quick question about yoke phasing, but first some background...

I've been chasing an oscillating vibration on my car since I assembled it that starts in gently at around 2500 in high gear and gets progressively more intense the higher up in RPMs I go. I only feel it when I'm cruising along on the highway and it'll rattle your teeth at 4000. If I'm running WOT, either it's lessened or I just don't notice it because I'm busy.

I recently took the shaft into a local driveline shop to have it checked and get the U-joints replaced and I noticed the yokes on the shaft are visibly not aligned. Not severe...maybe around 5 to 10 degrees, but enough to notice just eyeballing it. I asked them about it when I dropped it off and told them about my issue, they told me "don't worry about it".

Well, the shaft is back in the car with fresh joints and the vibration is exactly the same as it was before. I've tried changing the pinion angle and added/removed shims under the trans mount with no effect on the vibration.

Could the yokes be the issue? My engine/trans mounts are only a couple of years old and, eyeballing from the rear, it looks like the pinion is in line with the transmission. I could try swapping the center section or borrowing a set of tires, but I've been through the tires before with no luck.

Thanks for any assistance.
Click to expand...
and you should be in the 11s with no trouble
 
Well, I dug up the angle finder and it looks like my eyeball needs to be calibrated. The difference between the front and rear welded yokes on the shaft are, at most, a half degree different. I'll be looking elsewhere for the source of the vibrations. Thank you to everyone for answering my questions on this.
 
Have you taken it to Sadler DriveTrain out by the airport. Take it there and tell them what problems you are having. They can fix it up and you'll have it back in b/4 the weekend. (Hope to see you there on Sunday) tmm
 
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