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Discussion Starter · #1 ·
I know the accepted u-joint operating angle is 2 degrees or less but does anyone have what I have of 3.5 degrees of u-joint operating angle? This is on a 66 Malibu, 327 mild build, TH350 recent rebuild with shift kit, complete front end rebuilt, brand new 3" mild steel driveshaft, new Spicer u-joints/slip-joint, brand new Quick Performance 9" Ford rear with 4.11 gears, new Massive Energy adjustable 4 link and new Calvert single adjustable race shocks. I've been chasing a vibration for a while now which is a busing type vibration and thinking it is either the u-joint operating angle which I can't change or my new 60.5" mild steel 3" driveshaft which the Critical Speed Charts suggest because it starts vibrating at 4500 to 4700 rpm. My engine/transmission is 3.5* down, DS is .5* up and the pinion is pointing up 3.5* which means it's a negative. I haven't checked my wheels and tires yet because it's more of a busing vibration. The phasing of the welded yokes on the driveshaft are 1* off and I called the builder on that he said it's fine. I plumbed the crankshaft, trans output shaft and pinion shaft to get everything in line. Looking for help please, going crazy.
 

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I have set up a number of vehicles with 3 degrees +/-. My target number is usually 3 degrees, not 2. I have not experienced vibrations with the 3-5 degree set-ups. I think you are good on this.

Currently in my '66 I have a very similar setup as you do, with one exception, I'm running a 4" aluminum driveshaft from Denny's Driveshaft Service in NY which he did machine balance for high RPM.

I would ask what you are running for engine and trans mounts? Some people have found running Poly engine and trans mounts together will get some harmonic vibrations. I have set this car up with a traditional rubber trans mount, and Poly engine mounts for that reason.

It sounds like your setup is pretty typical. Make sure your yoke has a good stick-out in the trans (not bottoming), and make sure your convertor is not bottoming in the pump (you need at least 1/16") as both instances will give vibration.

Other simple things to check for a buzzing vibration, make sure your headers are not touching the frame, sounds basic, but I know I have had to "clearance" more than one set of headers in the past for an issue like this. When you torqued the rear suspension, you did it with the suspension loaded, and not hanging?

I can only offer this advice, go over everything from back to front. I would suspect if it is in the driveline, you will find it.

Once thing I did chase when I built the car last year were the Ford drum brakes on the QP 9". This I did have a vibration with, and was able to fix. If you did get the drum option on the rear, I can step you through what I found.

Tom
 

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Is your pinion higher than the trans or lower? On my 67 the pinion was higher even with the 9". I ended up with a CV driveshaft and that took care of the vibration.
 

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Discussion Starter · #4 ·
Thanks Tom, I did get the drum option from QP. I really wasn't happy with QP, waited 3 + month for the build, which wasn't a big concern, but when I received the center section it was missing most of the bolts on the pinion/seal cover and when I talked with them, they said I need to send it back. They had video documentation of their process and said it was missing the O ring and the backlash was not set. One of the ears for the upper control arms is weld in the wrong place and the bushing was installed crooked. I didn't tell them about that one which could be my issue. I have race ramps and the car was sitting on them for all my torquing of the control arms. I would like to know how you solved the drum out of balance. Thanks,
Tim
 

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My QP 9" came in 5 1/2 weeks last fall. Zero issues. I've got over 5,000 miles on it. I have the 11" disc brakes though.
 

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Discussion Starter · #6 ·
Is your pinion higher than the trans or lower? On my 67 the pinion was higher even with the 9". I ended up with a CV driveshaft and that took care of the vibration.
Yes, my pinion is higher than my drive shaft and I have a hard time living with that because it just doesn't seem right. Where did you get your CV DS and how much is something like that? I'm leaning toward a driveshaft problem, and that really ticks me off because of the $400 for it three weeks ago and probably another $600 to replace it.
Tim
 

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Yes, my pinion is higher than my drive shaft and I have a hard time living with that because it just doesn't seem right. Where did you get your CV DS and how much is something like that? I'm leaning toward a driveshaft problem, and that really ticks me off because of the $400 for it three weeks ago and probably another $600 to replace it.
Tim

That's a dirty little secret on A bodies. Some of the extreme pro touring I don't know how they get away with it. So your operating angle is 4 degrees if I'm thinking right. CV was from the driveshaft shop. Just under $1,000. Took 9 weeks to get.
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Discussion Starter · #8 ·
That's a dirty little secret on A bodies. Some of the extreme pro touring I don't know how they get away with it. So your operating angle is 4 degrees if I'm thinking right. CV was from the driveshaft shop. Just under $1,000. Took 9 weeks to get. View attachment 724499
That is really nice looking but I don't think I want to spend the money right now.
 

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Discussion Starter · #9 ·
I have set up a number of vehicles with 3 degrees +/-. My target number is usually 3 degrees, not 2. I have not experienced vibrations with the 3-5 degree set-ups. I think you are good on this.

Currently in my '66 I have a very similar setup as you do, with one exception, I'm running a 4" aluminum driveshaft from Denny's Driveshaft Service in NY which he did machine balance for high RPM.

I would ask what you are running for engine and trans mounts? Some people have found running Poly engine and trans mounts together will get some harmonic vibrations. I have set this car up with a traditional rubber trans mount, and Poly engine mounts for that reason.

It sounds like your setup is pretty typical. Make sure your yoke has a good stick-out in the trans (not bottoming), and make sure your convertor is not bottoming in the pump (you need at least 1/16") as both instances will give vibration.

Other simple things to check for a buzzing vibration, make sure your headers are not touching the frame, sounds basic, but I know I have had to "clearance" more than one set of headers in the past for an issue like this. When you torqued the rear suspension, you did it with the suspension loaded, and not hanging?

I can only offer this advice, go over everything from back to front. I would suspect if it is in the driveline, you will find it.

Once thing I did chase when I built the car last year were the Ford drum brakes on the QP 9". This I did have a vibration with, and was able to fix. If you did get the drum option on the rear, I can step you through what I found.

Tom
I might have to try the rubber trans mount, right now I have poly body mounts, engine mounts and transmission mount. Yoke, converter and headers all good. Not sure if the rear drums are out of balance.
 

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That is really nice looking but I don't think I want to spend the money right now.
Yea the 9" and the CV driveshaft was definitely not in my budget. I did put over 4,000 miles on it this summer so I guess it was worth it. I did get a lot of vibrations out with a standard shaft by adjusting the upper control arms to adjust the pinion. This is while I was waiting for the CV shaft.
 

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I might have to try the rubber trans mount, right now I have poly body mounts, engine mounts and transmission mount. Yoke, converter and headers all good. Not sure if the rear drums are out of balance.
My drums did not really appear to be out of balance, but were definitely out of round, which is common. Before I assembled it all I did get the drums turned.

I put it all together, ran it and had a vibration, not real noticeable, but could be felt al all speeds. I farted around looking at everything again, could not find any driveline issues. Drove it about (3) weeks like that and in feeling the back drums, they were usually hotter than I liked, not so you could smell them, but too warm for the amount of driving, and more so on one side.. Long story short the drums still seemed to have a high spot, but I felt it was not significant, so swapped drums side to side and the heating did not go with the swap.. time to look inside...

What I ultimately found was with everything assembled the pads were digging into the backing plates, and not allowing the pads to float on the backing plates... "off shore" tolerances must have been strong in all the parts. What I did was flapwheel the pads on both sides and flapwheel the backing plate pads... the heat on the drums, and vibration went away....pretty simple, once I found the problem.....might be worth checking....
 

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CV joint is the way to go. It not only makes HP loss minimal but there are no vibrations. With my 2014 Shelby Ford did away with the two piece driveshaft and replaced it with a one piece Carbon Fiber CV driveshaft. That car did 202mph and Ford claimed all two piece units had to be speed limited at 155mph
 

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Discussion Starter · #13 ·
That's a dirty little secret on A bodies. Some of the extreme pro touring I don't know how they get away with it. So your operating angle is 4 degrees if I'm thinking right. CV was from the driveshaft shop. Just under $1,000. Took 9 weeks to get. View attachment 724499
I'm curious what you installed your 9" QP in and if you had any problems. I'm thinking mine was built wrong, I had to move the hole thing over 1 1/2" to the drivers side to line up my engine/transmission and driveshaft.
 

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Most Ford 9" rears have a pinion offset of 15/16 (.9375" or 23.812mm) to the passenger side and is completely ok in most situations. To account for your remaining .5" could be engine or trans mount alignments or frame. usually those minor .5" issues can be corrected by adjustable upper control arms on the rear. But then you may have tire rubbing issues pending tire widths and body not straight on the frame.

My 70 has a QP9" and 3* rear pinion difference with no vibrations.

Mike
 

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Discussion Starter · #15 ·
Most Ford 9" rears have a pinion offset of 15/16 (.9375" or 23.812mm) to the passenger side and is completely ok in most situations. To account for your remaining .5" could be engine or trans mount alignments or frame. usually those minor .5" issues can be corrected by adjustable upper control arms on the rear. But then you may have tire rubbing issues pending tire widths and body not straight on the frame.

My 70 has a QP9" and 3* rear pinion difference with no vibrations.

Mike
Thanks for the info, I started out with it centered in the frame like the 12 bolt axle but my DS builder said the pinion needs to be inline with the transmission output shaft. I started moving it over a little at a time and testing with no luck so I loosened the motor mounts, transmission mount and unbolted the exhaust from the headers to try and move the engine/transmission over, it gave me a little but not much. The way I have it now is 3 1/2" tire to frame clearance on the drivers side and 1/2" on the passenger side. That gives me a straight line from engine/transmission to the pinion shaft. But I still have a vibration at 85-90 mph which is a buzzing type of vibration. I had a talk with the DS builder, they sell a lot of race axles and drive line equipment, but he never heard of the Critical Speed Chart and they only do a 500 rpm balance on driveshafts. My driveshaft is about 61" long center to center which is off most Critical Speed Charts. I think I wasted $400 and should have gone to a CV type DS.
 

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When I talked to QP he said they set the pinion centerline where the original 12 bolt was but the 9” pinion is about 3/4” lower than the GM.
 

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10 bolt and 12 bolt rears have a 1/2 or .5" offset. So technically the 9" is only .5" more. I have never had a vibration because of the offset left to right. And if your DS builder has never heard of Critical Speed of a DS and only balances at 500rpm, I'd be finding a different DS guy.

If I was you, I'd be looking for another issue than the left/right offset.

Mike
 

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I don't believe the center big part of the rear end on my 9" is centered in the car. I also don't think the pinion is centered in the frame but I never measured it.

How the heck were you able to adjust the rear that far over and what was the plan if that magically fixed it?
 

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Discussion Starter · #19 ·
10 bolt and 12 bolt rears have a 1/2 or .5" offset. So technically the 9" is only .5" more. I have never had a vibration because of the offset left to right. And if your DS builder has never heard of Critical Speed of a DS and only balances at 500rpm, I'd be finding a different DS guy.

If I was you, I'd be looking for another issue than the left/right offset.

Mike
Okay I just came in from the garage and I moved my rear end back over and set my pinon angle to 3.2* down, drive shaft is .5* down and engine/trans. is 3.4* down. When I say down on the pinion it's pointed up but the correct way to plug it in Spicer's Calculator it is down. I'm going to have my wheels road force balance before the next test drive and probably start thinking about another drive shaft, I don't have a lot of room in the tunnel so I'm going to have to do some measuring to see if I can get a 4" in there or even a CV style. Definitely with a different DS builder like Denny's.
 

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So below is what you get? I think those angles look great ! The angles are really close to being 'Phased'. When people talk about the 3 degree rule, its when there is a greater than 3 degree difference between the two angles.
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Mike
 
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