driveshaft bent???

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Daves67Cuda

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so i had my car lifted up and had it running because i was having issues with the transmission and whatnot. well when i shifted into 4th gear, like the whole rearend was shaking and my dad said it looked like the driveshaft my be bent some. any one have this problem before? dont wanna ruin anything else on my car. thanks, dave.
 
Never had a bent DS, but wouldn't be too hard to just pull off and roll it across the garage floor to see what it looks like.
 
With the suspension hanging you may well have been binding the rear u-joint causing the housing to want to "wrap" back and forth. If your going to operate the drivetrain while lifted, lift via the rear end so the car is sitting on it's suspension. Then eyeball it while running from behind and underneath and you should be able to tell how true the shaft is.
 
If you support the rear end (as mentioned above) you could put a dial indicator on the driveshaft and roll it over by hand to check for runout. Or just do it visually. Are you having vibration issues? If the driveshaft is bent you will have a speed related vibration.
 
I twisted the driveshaft in my dad's 73’ mach 1 before, at Friday night drags at the strip. The car hooked like mad and it was the first time I managed to get the fronts off the ground.

But that was a very noticeable thing, you could tell what the problem was right away
 
yea, the rear end definitely was just hanging. i gotta put a new throw out bearing in, hopefully wednesday, once i get it in, i'll see if i can do it with the rear end supported like on jacks. didnt really think anything about it just hanging either tho, thanks for all the info. i'll let you guys know in a few days how it turns out. dave
 
TheBestCar said:
With the suspension hanging you may well have been binding the rear u-joint causing the housing to want to "wrap" back and forth.
Click to expand...
So what happens when you're just runing it down the road over say, a big wallow under an interstate overpass? I thought the suspension was designed to operate through the full range of motion.
 
Ace said:
So what happens when you're just runing it down the road over say, a big wallow under an interstate overpass? I thought the suspension was designed to operate through the full range of motion.
Click to expand...

An engineer, yet you do not grasp geometry or dynamic vs. static. How odd.

How often do you go over "huge wallows" that cause your suspension to go into full droop (the position it is in when you have the suspension just hanging up on a hoist) for any length of time? You must be Evel Knievel or something I am guessing.

There is a reason all motor vehicles have a recomended ride height, and it has to do with how all the drivetrain and suspension components work together and how long the will do so, not how cool it looks.

Drivetrain's are designed to operate at a given ride height, they can travel thru a range but that does not neccesarily mean you can run it in that range for an extended period.
 
I would agree with Ace that the U-joints won't bind as long as the suspension is within it's full range of motion. Althought I would also agree if you run a car with the wheels off the ground you should have the weight on the rear end, like up on stands.


Chuck
 
Looks like we got another troll hanging out here wanting to share their wealth of crackpot knowledge, and provide no profile information whatsoever. Yeah, I'm an engineer. Probably been one since before you were wet behind the ears, Mr. "Best Car." What kind of car you driving anyway? What do you do for a living? Inquiring minds want to know!!

OBTW, the E-470/I-25 intechange here has some serious irregularities where the pavement surfaces were improperly re-joined after several rounds of construction. They definitely flex the suspension all the way up and down on most vehicles and MILLIONS of vehicles go over them on a regular basis. I do every day going to work, although not in the Duster. It gets the back wheels off the ground in my truck if I'm going fast enough.
 
340mopar
Maybe the term bind was to "strong" a word, I should have been more detailed and said
"As you adjust the operating angle of the u-joint (by lifting the vehicle, shimming the rear axle, etc) you are also changing the elliptical path that the u-joint must travel in. The greater the operating angle, the less like a circle the path of the ellipse, and the greater the torsional vibration caused by the u-joint"
But then I would have had to include that this is a qoute from Driveline Basics with Steve Johnson and I just thought that was to much and said bind instead. My bad.



Real nice, Ace.

Quick to insult and easily offended, even though all I said was that I felt it was odd that a person who claims themselves to be an engineer dosn't understand three simple things in regards to suspensions, demonstrated by how you responded to the post.

Seems like the only troll here, is you. Trolling for a fight, with your insults and implications that someone could not know more than you regarding a subject, just because they choose not to plaster info about themselves all over the internet and because you have a self-rightous, greater than all, attitude because "yeah I'm an engineer". Whatever. Go troll elswhere.
 
I usually stay out of these, but seriously TheBestCar, you don't think that your reply was a bit snide? You couldn't have just explained it without the extra commentary? No need to start another war....:boxing:
 
I'll try to get this topic back into perspective, to see if we can possibly help Dave out here.
A few things I would look into, would be "U" joint wear, driveshaft should have a balance plate spot welded to it, and leaf spring bushings. All of these will cause vibration, and make it look like the driveshaft is the culprit.
Start with the basics Dave, work from there.
Good luck, keep us updated.
Hope this helps.
 
How ya doin? Managed to get yourself banned huh?. And still gunning for me. Wonder how long it will take this time. :finga:
 
Just my 2 cents,if you dont have a vibration when driving ,its probably not bent all that bad,however,if you do,send the driveshaft out,sometimes the shop can sraighten,and rebalance it for you, good luck!
 
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