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Can a front driveshaft that's too short cause vibes?

DeftwillP

DeftwillP

NAXJA Forum User
Location
Round Rock TX
I'm on 6" of lift. I regeared to 4.56 over a year ago. I immediately noticed a "slow pulsing" vibe at around 60+ mph. It would leave whenever I would disconnect the front shaft and go out for a spin. I went to a driveshaft shop and had them balance it. It got a little better, at least to where it was tolerable to keep up with traffic.

A few months ago, I added drop brackets to fix some ride and flex issues. This, you'll notice, pushes the front axle back out to its correct location. I have to force the front shaft out to fully extended just to be able to connect it now. And the vibes have gotten bad again.

I realize that going to 4.56s raised my rpms which can help amplify vibes that you may have never noticed. Would getting my shaft lengthened :roll: help this? Or is it more likely some sort of gear set up problem?
 
My bet would be to get a longer shaft. i had the same problems when i first put my lift on the first few weeks cause shipping took forever for my new driveshafts to come. soon as i put them on bam no more vibration in my rig.
 
Hmmm....then this could possibly be the answer. Anybody else wanna chime in?
 
also if you've gotten new tires since then as well if they are unbalanced etc at higher speeds they will wobble causing vibration.
 
Nah, same old 32" bfg a/t's. Won't seem to wear out.

Would unbalanced tires cause vibrations only at higher speeds? It would seem like they'd be noticeable at all speeds.
 
usually (not always) unbalanced tires would vibrate around a certain speed, and again usually at higher speeds, yes (that speed varies from tire to tire) i used to have 31 10.50 BFGoodrich AT's and at first they would only vibrate from about 46ish to 50ish any slower and faster than that it wasnt noticeable.

Whatever the case end up being you cant go wrong with a longer driveshaft anyways, since it will be stronger, less stress put upon it, and have more wiggle room just in case you put your rig in a flexy situation ;)
 
I see. Well it cost me $50 to have this shaft balanced. I wonder what it'll be to lengthen it another inch or so?
 
Seems like it would be something else im at 8 inchs and have plenty of driveshaft left mabye tires are culprit mabye put rears on front and other see if it changes it any.
 
control arm drop brackets where added and you got vibs? what did you set the pinion and caster angle to? how about bad driveshaft ujoints?
 
I'm going to vote with 89, if you left the pinion at close to stock, you probably have some harsh driveline angles going on. Correcting pinion angle will of coarse reduce castor an the front end will tend to wander.
 
front pinion angle should be fairly straight if you're still using a cv front shaft, the pinion should point straight thru the d-shaft, might not be so good for steering, but give a little get a little
 
The pinion angle looks like its in good shape but thats just from eyeballing it. I know thats not an accurate way to tell but I don't have an angle finder.

Like I said, I had the vibes before db's. But they've changed in their severity over the changes. Oh, I changed one of the ujoints to no avail.
 
I'd bet on pinion angle or shaft length. If the shaft is too short and is at the limit of its extension, first of all you're going to lose it the first time you stuff the passenger tire and drop the driver side, second, it's got very little spline engagement and so it'll have more sideplay. This can increase vibrations. A longer driveshaft may help but you might also need a longer spline section in the middle to allow the suspension to flex over the full range without either popping the spline joint apart or bottoming it out. Flex it out and mock it up and see what numbers you end up with.
 
my front shaft is too short. splines are starting to show just sitting there. i have longer lcas and ucas and have fully flexed the front with no issues of the front ds pooping out... i do have some tire vibes....but no vibes from the shaft, the same vibes stay there when i pull it off. i do grease it before every trip to be safe. i may eventually lengthen it, but i will be going to longer lowers and hope i wont even have to worry about it anyway at that point...
i wouldnt worry . the lengthen and balance a shaft is around 100$ here, depends on lenght, and you have to get it balanced when you lengthen it,(new tube means new balance)
 
odds are that when he says he removes the shaft the vibes go away so I would lean towards the shaft being the problem
 
What are your driveshaft angles?Whats your castor?Do you have a t-case drop?
 
RCP Phx said:
What are your driveshaft angles?Whats your castor?Do you have a t-case drop?
Click to expand...

As I stated earlier, I don't have an angle finder at the moment so I can't readily offer those numbers. I have a sye, so no tc drop. It's definitely front as well.
 
DeftwillP said:
As I stated earlier, I don't have an angle finder at the moment so I can't readily offer those numbers. I have a sye, so no tc drop. It's definitely front as well.
Click to expand...
I realize that,thats why I asked about the t-case drop since that can make front driveline issues worse.

Bottom line:You need a 3$ angle finder and you can check everything!
 
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