Driveline Vibration
1975 F100- Long bed. We've got a drive-line vibration that starts about 45mph and continues to get worse as mph increases. It isn't as bad under acceleration but holding a steady speed and coasting it is. I forgot to add; IT IS MPH DEPENDENT not RPM dependent.
Drive-shafts have new u-joints, new swing bearing and have been balanced. Rear housing is a new Currie 9in with all new stuff in it. Transmission is 3 speed. The motor has been balanced. Thanks. |
You sure it's not the wheels out of balance?
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Thanks. That's one thing I forgot to add. They were mounted and balanced by a shop. Aluminum wheels.
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"Where" are you feeling the vibration?
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New and balanced everything? How's the driveline angles? If you hit the pinion angle too steep, it could cause a vibration. Also, "new" doesn't mean "good". Your rear could have too much back lash in the gears. You could STILL have a bad u-joint. The output shaft of the transmission could have a bad bearing. The center bearing could have torn rubber or not fit the shaft correctly. You need to go through every part and systematically check off each one. I bet when you go through everything, you'll find something you missed. What about tires? You didn't say they were new, just that they were mounted and balanced. Could one of them have a belt separating?
I'm just giving you ideas since I'm not standing there, looking at the truck. Let us know what you find. |
I had my new tires mounted and balanced by a shop. They still balanced them incorrectly, and caused a vibration.
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Gents, thanks for responding; great ideas. So, yes the tires were new and still don't have many miles on them. We bought them brand new. It feels like the vibration is coming from the center of the truck if that makes sense. We had the diff set up by a drive-shaft shop that specialized in rear ends and drive-shafts.
The rear is an all new Currie housing ordered directly from Currie with their Trac-loc diff. Original 3.25 gears used. New 31 spline axles. The rear drive-shaft was custom made by the same shop. The original front was reused. So later, after we still had the vibration, we re-balanced all four wheels and tires. I took the whole front and rear drive-shaft out and had all new u-joints replaced, swing bearing replaced and the whole thing balanced. Now I haven't changed the pinion angle from stock. I haven't checked internally in the trans. I haven't changed the trans mount. I haven't looked at the flywheel, clutch kit or pilot bearing since we replaced it all. |
Could the u-joints be out of phase?
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What is "u joints out of phase"?
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U-joints being out of phase is when the u-joints on a drive shaft are not lined up, or not clocked the same.
http://www.speeddirect.com/Steeroids...%20PHASING.jpg |
How many u-joints are in your rear drive shaft?
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I just checked mine and the front is definitely out of phase with the rear two, as I was completely unaware of this "phase" thing upon installation. How serious of a problem is it?
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Sorry guys, A LOT of yard work yesterday. I'll have the check the phasing. The truck is at my dad's house. I do know when they balanced the ENTIRE shaft at the driveshaft shop, they aligned the slip yoke together with 2 arrows.
It's a long bed. So if I'm remembering right, there is one joint right behind the output shaft and 2 in the the rear shaft; one right behind the slip yoke and of course another at the pinion flange. Right? |
Thanks - good to know
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Originally Posted by Greenhiboy
(Post 14233932)
Could the u-joints be out of phase?
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The only thing not mentioned that I can think of is check the pinion angle. If you recently installed a new housing there is a chance the pinon angle was not checked, its very possible that the spring perches are angled different from the original housing. If the pinon angle is wrong it needs to me shimmed with wedges to correct it.
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Thanks for the reply. Well I would expect a company like Currie to know what they were doing with building a 9". I talked to a couple different builders and told them stock everything but I guess it could still be possibility. What is stock pinion angle and where do I need to measure it from?
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Learned something new today!
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Nice. Sounds like could definitely be a possibility according to the article. It stated more vibration under acceleration (pinion tipping up) a less under coasting. Ours is just the opposite; more under coasting (pinion tipping down). I'll check it. Thanks.
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So not much of an update really. I had CalTracs build us a kit for the truck which should help us with initial off the line traction. But I know I need to measure the pinion angle before I get the kit installed. I originally thought I could use the kit to dial in some pinion angle and John at CalTracs said that wasn't at all what the kit was for. Then he informed me that I should be looking for about 2° negative pinion angle.
Is that what most trucks are running for appropriate pinion angle for 2wd? |
I had two experiences of such. The first case was a case of improper balance and a bent wheel (it was the spare tire) The second was a little more serious, a bent driveshaft. In that case, the previous owner's kid like to jackrabbit start and hot rod it, pop the clutch, etc. Of course I didn't know about this until after I bought the truck. After a junkyard replacement, it was fine.
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If the vibration only starts at 45 and is not at lower speeds, then it should not be your pinion angle. A pinion angle vibration would be detected at all speeds. It is still a good idea to make sure your pinion angle is set correctly. Do a google search for "pinion angle" and select the images link for it. You will get all kinds of pictures showing how to set it up based on the type of drive-shaft you are running.
In order to find a vibration, I always recommend removing the front drive-shaft and go for a drive, if the vibration is gone, then it is located in the front end somewhere, if its not gone, then re-install the front drive-shaft and remove the rear drive-shaft and go for a drive. If the vibration is gone then it is located in the rear. Once you know where the vibration is located, start looking for worn, bent, broken components. Usual suspects are: u-joints, drive-shafts, axle shafts, bushings, bearings. If the vibration remains when the front drive-shaft is removed and also when the rear drive-shaft is removed then you need to look at the transfer case, transmission, their respective mounts, tires, rims, etc. I know this was long, but the basics are to remove the drives-hafts one at a time to determine if the vibration is in the front or back. Do that and then let us know the results. |
That sounds like a great idea except if I remove the driveshaft, the truck won't move. It's a 2wd.
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So I found this. I think it's pretty telling.
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Originally Posted by Justin Jones
(Post 16093242)
That sounds like a great idea except if I remove the driveshaft, the truck won't move. It's a 2wd.
Time to start checking for loose, bent, or broken components. |
No harm done. I appreciate you taking the time to write the post. The ideas that I have are the pinion being at the wrong angle, a bent axle flange, a worn transmission mount or a worn tail-shaft bearing in the trans.
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This has been on my mind lately for some reason but I haven't had a chance to get under there and check the angles with the truck being at my dads. So when I do get a chance to do some angle measuring, what are the angles at the pinion flange and trans output shaft am I looking for?
The tech at CalTracs said I should be shooting for 2° negative on the rear end pinion flange. Does this sound like the most common measurement? |
Yes...1 - 3 degrees down-angle is about right, presupposing the trans output shaft is close to the same and in phase. You could try flipping the driveshaft 180 degrees to see if the vibration goes away...
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