Changed d/s, now vibration
Thread Starter
Joined: Jan 2002
Posts: 1,802
Likes: 36
From: Dutchess, New York
Changed d/s, now vibration I just swapped out my stock d/s for a 3" chromolly one. I took it on the highway and i'm getting a slight vibration at 75-80 (haven't had a chance to take it higher) under load, a worse vibration coasting, and even more worse with the clutch disengaged and coasting. I double and triple checked the u-joints and yokes after install and they seem tight and fully seated, and I'll undo them again and rotate it 180 degrees and see if it helps. Is it possible I overtightened the nuts on the U-bolts holding the joint to the yoke? If not, what else can I do? Would a local shop be able to balance it? Or am I stuck trying to return it and get another?
Also whats the danger of driving like this - I imagine it can't be good. So far I only drove for ~6 miles at ~65 with a few burts to 80 to create the vibration. I'm worried its going to chew things up in the drivetrain (notably the $2500 Moser!).
Also whats the danger of driving like this - I imagine it can't be good. So far I only drove for ~6 miles at ~65 with a few burts to 80 to create the vibration. I'm worried its going to chew things up in the drivetrain (notably the $2500 Moser!).
If you over tightened the u joint caps on the back it will vibrate like hell. The spec for those is very sensitive. Try loosening the caps up and see if that helps.
Thanks
Thanks
Originally Posted by Chris@AP-Engineering
If you over tightened the u joint caps on the back it will vibrate like hell. The spec for those is very sensitive. Try loosening the caps up and see if that helps.
Thanks
Thanks
I have some vibrations around 80 mph but i just installed a SPohn Adjustable TQ arm mounted to the crossmemeber. I tired messing with the pinion angle without much luck
I have the same problem with my car. I just put in a 4th gen Moser 9" with a LS1 DS and mine vibrates at about 75-80. I've been driving like this for awhile... trying not to go that fast. I know how much I hand-tightened them and I bet its too much. What is the correct tq?
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Thread Starter
Joined: Jan 2002
Posts: 1,802
Likes: 36
From: Dutchess, New York
UPDATE:
Well took it to a shop, and they spun the d/s and said its dead nuts on, so the d/s itself isn't causing the vibration. So maybe a u-joint? Or incorrect torque on those nuts - but I have no idea how to fit a torque wrench in there. Not sure where else to look, only other thing I can think of is the heavier d/s just makes an existing imbalance somewhere else more noticeable.
Well took it to a shop, and they spun the d/s and said its dead nuts on, so the d/s itself isn't causing the vibration. So maybe a u-joint? Or incorrect torque on those nuts - but I have no idea how to fit a torque wrench in there. Not sure where else to look, only other thing I can think of is the heavier d/s just makes an existing imbalance somewhere else more noticeable.
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TECH Regular
Joined: Jan 2003
Posts: 466
Likes: 1
From: Bay area, Ca
did you put the stock one back on? put the original one back on and see if it stil vibrates.
ive been having a prob with vibratating for so long now i spent more then 500 trying to figur it out and finally tried using my freinds DS and solved my prob. waitng for my LPE to come in hope it solves the problem.
good luck and keep use updated
ive been having a prob with vibratating for so long now i spent more then 500 trying to figur it out and finally tried using my freinds DS and solved my prob. waitng for my LPE to come in hope it solves the problem.
good luck and keep use updated
Thread Starter
Joined: Jan 2002
Posts: 1,802
Likes: 36
From: Dutchess, New York
I put the stocker back on and its fine again up to 80ish. Going to try another 1350 u joint on the replacement shaft. Only other thing I noticed is on the aftermarket shaft, the yoke that goes into the output shaft (or should I say the output shaft goes into), is about 1/4" shorter than stock. Other than that and the u joint, I have no idea what else could be causing this. Might just throw it on for a few passes down the track on Mickey's, then swap back the stocker for the street.
Thread Starter
Joined: Jan 2002
Posts: 1,802
Likes: 36
From: Dutchess, New York
Lol its about at the point where I'm just going to launch the **** out of the car at the track, and if the stocker pretzels, bring this as a spare, swap it in and drive home at <75 mph. 
Launching!
Joined: Oct 2004
Posts: 251
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From: Ohio
Originally Posted by NHRATA01
UPDATE:
Well took it to a shop, and they spun the d/s and said its dead nuts on, so the d/s itself isn't causing the vibration. So maybe a u-joint? Or incorrect torque on those nuts - but I have no idea how to fit a torque wrench in there. Not sure where else to look, only other thing I can think of is the heavier d/s just makes an existing imbalance somewhere else more noticeable.
Well took it to a shop, and they spun the d/s and said its dead nuts on, so the d/s itself isn't causing the vibration. So maybe a u-joint? Or incorrect torque on those nuts - but I have no idea how to fit a torque wrench in there. Not sure where else to look, only other thing I can think of is the heavier d/s just makes an existing imbalance somewhere else more noticeable.
I think it would have to be a heavier shaft, and there will
be more vibe put onto the yokes as the U-joints turn.
The poly trans mount is going to make this more noticeable.
Curious whether setting up for a zero pinion angle would
decrease it or not.
be more vibe put onto the yokes as the U-joints turn.
The poly trans mount is going to make this more noticeable.
Curious whether setting up for a zero pinion angle would
decrease it or not.
Launching!
Joined: Oct 2004
Posts: 251
Likes: 0
From: Ohio
Originally Posted by jimmyblue
I think it would have to be a heavier shaft, and there will
be more vibe put onto the yokes as the U-joints turn.
The poly trans mount is going to make this more noticeable.
Curious whether setting up for a zero pinion angle would
decrease it or not.
be more vibe put onto the yokes as the U-joints turn.
The poly trans mount is going to make this more noticeable.
Curious whether setting up for a zero pinion angle would
decrease it or not.
But aluminum "grows" more with heat and flexs more than steel and also a a alumiinum shaft itself "resonates" easier and tend to conduct more noise and vibration than a steel driveshaft does as the heavier steel shafts have a damping effect.
I agree with snoman on the damping thing. Having more rotational mass would be similar to having a larger (in diameter) driveshaft in there, like an LPE 3.5" piece. The further from the center of the DS the weight is, the more effect it will have on the damping.
I have the same problem NHRATA is having, but mine developed on it's own. Nothing was changed in the time that the problem developed.
I have the same problem NHRATA is having, but mine developed on it's own. Nothing was changed in the time that the problem developed.
Originally Posted by snoman
Very true, aluminum is great stuff in some uses but it is not a "stable" as steel in driveline components.
shafts are at the vibration frequency he's talking about
here. And as to why the "better" steel shaft would make
vibration worse, I can't surmise on the materials basis?
Still think it has to do with the mass the U-joints have
to push around, pinion angle and maybe the absolute
joint angles in this case.