Problem vibration after u-joints replaced......please help

mytight95

mytight95

Active Member
Apr 11, 2003
2,605
0
46
Dothan,Al
#1
I took my driveshaft out of my car friday and took it to have the u-joints replaced as they were squeeking, i didn't get a chance to reinstall the driveshaft and take it for a test drive until today......well now i have a severe vibration :fuss: that seems to be MPH related, so i was thinking sine the vibration is only from~49mph or so up, maybe if i put it in fourth gear 1:1 ratio it won't be so bad....turned out to be true, so anyone have my solution or any advice, only thing i can think is that they didn't put in the right joints...... :nonono:

I marked the driveshaft upon uninstalling it as to not throw off the balance, and reinstalled it with the marks aligned as it's supposed to be....Nothing else was done to the car other than DS R&R......

please help



ps: i must add that the car is extremely smoother up to about 50 where the vibration starts than it was and a lot smoother under accelleration, so i don't know what it is :shrug:


thanks

jason
 
#4
um, did you mark each section (on either side of the joints) and ask the shop maintain that relative relationship? otherwise, your having marked the DS flange to pinion flange relationship does not do a whole lot.

i might have the rotating mass dynamically balanced - decent driveline shops can do this.

you can also try indexing the DS as it is or try applying weights, if you can figure out where the imbalance is. was the DS checked for run out?

good luck.
 
#5
I don't know about the runout stuff etc........ I had a very reputable shop do this as i have lost a DS going around 100mph before, and this is the reason i didn't do the install myself........lol

if i have to go through the trouble of having it balanced and all that, I think i will demand a refund or something and just buy aluminum...... Already got 70$ in the u-joints and their install........I also thought that the reinstallation of new u-joints would negate the having to install a certain way thing, IM LOST....


jason
 
#8
Was it vibrating also before you replace the u-joints? If so, you may need to have the shop balance the drive shaft. If too costly, yes you can purchase an aluminum driveshaft. Is it me or did Ford double the cost of its' aluminum driveshaft? I remember paying about $125 some years ago.
 
#10
yep, gas prices apparently follow alum DS prices.

the rotating assembly is only loosely balanced at the factory - nothing high tech.

it is actually quite common for a DS to get bent a little bit (road debris, hitting the undercarriage, etc). either gotta have a shop true-it, have a new one made or buy a new one. ditto for new gears and the associated increase in DS rpms (getting closer to to critical speed) to show balance issues.

and if you are worried, a driveshaft loop might be a good idea and provide a little piece of mind.

good luck with it all.
 
#12
don't know, but i think i will know upon returning to the shop........ I talked to the guy at the shop today and he was smartelic with me and stood firm that they did nothing wrong but would check it out..........


:this is bs!!!!!!

so now i have to find time to pull it out and make another trip up there with my schedule........ It took me 2 weeks to find time to take it the first time....


jason
 
#13
or you can have the entire assembly dynamically balanced. i think this is best as it balances the entire rotating assembly (trans, pinion, etc is all taken into consideration, not just the DS itself).

see the thing is that the DS is not necessarily intrinsically balanced - at the factory, it is 'matched' (read loosely balanced or pieced up) with other components so the entire assembly is roughly balanced. because of tolerances with other components that mate to the DS, the DS could be perfectly balanced but there would be vibes (think of a wheel and tire - you could get wheels that are perfectly balanced from the vendor. but once you put tires on, the wheel and tires assembly is not necessarily balanced, even though the wheel was perfect. same kind of idea).

good luck.
 
#14
oh yeah, point was that this is why i like to make sure that each half of the DS remains in the same relationship to each other part while doing U-joints (i end up with scribes on all the pieces, not just the flange. once the u-joints are off, you could accidentally rotate the halves and end up with the entire DS being out of balance, even though the marks at the flange match up. kinda make sense? i know i am kinda rambling.
 
#16
well if i have a bent shaft, they bent it..... I have a friends car here at my house that is having gears put in by another friend of ours........ WHile i had the oppurtunity today, i threw his driveshaft in the car and took it through the rpms and mps listed above....... Very slight vibration but nothing that feels like it is gonna jerk the shifter knob out of your hand like with my shaft...... Something is wrong!!!!! I am beginning to wonder if they didn't rotate it somehow.....somethings up, i don't get it...


jason
 
#19
get some gb weld,then place about an ounce of it on any given place on you ds,if the problem is worse,repeatr the procedure on the opposite side ,removing the old stuff, if you can tune it at all,then you know to take it off and get it balanced,or could it be your Fly wheel or clutch?
 
#20
chefster said:
get some gb weld,then place about an ounce of it on any given place on you ds,if the problem is worse,repeatr the procedure on the opposite side ,removing the old stuff, if you can tune it at all,then you know to take it off and get it balanced,or could it be your Fly wheel or clutch?
Click to expand...
or one can use a screw clamp (like you use on radiator hoses). the worm screw provides enough imbalance to allow one to quickly and easily try to get the thing balanced a little better.
 
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