recently i decided to purchase a 9 inch diff from central diffs in melbourne and have not been very happy with the quality. aside from the loud whining noise that my supposed brand new diff makes it also has a large amount of vibration. i have had my tailshaft balanced twice (the second time i stood next to the guy and witnessed for myself that the tailshaft was perfectly balanced). i have had my back tyres balanced on the fine setting (once again i stood next to the guy while he did it). yet at different speeds, and especially under load i get a large amount of vibration coming up through my seat. i would also like to note that when i put the diff in i replaced all trailing arm rubbers with super roo noepreme (i think) synthetic rubbers. i have noticed that the angle of my diff and tailshaft isnt perfectly straight but am unsure that this would be the cause of that much vibration as i have a 4wd with a 6inch lift, huge uni to diff angle and it doesnt seem to be as bad as this?
any suggestions would be really appreciated
annoying vibration problem
Started by
_raceme_
, Dec 30 2006 08:36 PM
22 replies to this topic
#2
_Yella SLuR_
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Posted 30 December 2006 - 08:40 PM
Ask em? Is there a run in period for a new diff? Could all just be a bit tight till it wears in, but I don't really know haven't done anything with my diff yet.
I did have a vibration problem, turned out to be a bent axle. Was only 70 thou (0.5mm) runout at the edge of the axle, but that transferred into like 5mm at the wheels.
I did have a vibration problem, turned out to be a bent axle. Was only 70 thou (0.5mm) runout at the edge of the axle, but that transferred into like 5mm at the wheels.
Edited by Yella SLuR, 30 December 2006 - 08:42 PM.
#3
A9X
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Posted 30 December 2006 - 08:42 PM
Back to centrals,
You've done everything else, what are you waiting for.
Welby
You've done everything else, what are you waiting for.
Welby
#4
_DocDamage_
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Posted 30 December 2006 - 08:50 PM
I recently changed gearbox & crossmember in the Bedford which resulted in a straighter angle between tailshaft & diff and also more high frequency vibrations. Chris Ryan from the beddy forum directed me here.
Tailshaft Angles
Hope it helps.
Tailshaft Angles
Hope it helps.
#5
surfmaster
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Posted 30 December 2006 - 08:53 PM
A dud uni joint perhaps, (not fitted correctly?).
#6
_Yella SLuR_
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Posted 30 December 2006 - 09:23 PM
^ you need to have new uni's to balance them properly. Worth asking the question I suppose.
#7
rodomo
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Posted 30 December 2006 - 09:28 PM
Tail shaft uni's suffer from a phenomenon called velocity fluctuations. This is a bit hard to explain but relates to the difference in speed of the yolks where the uni caps fit as the tailshaft rotates on an angle.
The "T" to the left represents the diff flange, the red dots represent the uni's.
The top picture is of a normal tail shaft as fitted at manufacture. The diff pinion is on the same plane as the yolk where it goes into the back of the gearbox. In this instance the velocity fluctuations of the 2 uni's cancel each other out.
In the bottom pic. the diff pinion is at a different angle to the gearbox yolk and in my diagram there is virually no angle at the diff end but still a significant angle at the gearbox end.
In this instance the gear box end uni is suffering velocity fluctuations but the diff uni none so there is no cancellation and vibrations can occur.
Clear as mud?
This might not be the problem but might help.
Good luck!
The "T" to the left represents the diff flange, the red dots represent the uni's.
The top picture is of a normal tail shaft as fitted at manufacture. The diff pinion is on the same plane as the yolk where it goes into the back of the gearbox. In this instance the velocity fluctuations of the 2 uni's cancel each other out.
In the bottom pic. the diff pinion is at a different angle to the gearbox yolk and in my diagram there is virually no angle at the diff end but still a significant angle at the gearbox end.
In this instance the gear box end uni is suffering velocity fluctuations but the diff uni none so there is no cancellation and vibrations can occur.
Clear as mud?
This might not be the problem but might help.
Good luck!
#8
ls2lxhatch
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Posted 30 December 2006 - 09:38 PM
I read a story in a car mag recently where a dyno was used to diagnose diff vibration. In the story they found that a person standing on the tow bar was sufficient to stop the vibration as it changed the gearbox/tailshaft angle. A few shims between the gearbox and crossmember fixed the problem.
#9
surfmaster
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Posted 30 December 2006 - 09:47 PM
I know, sometimes they can be incorrectly seated when installed. Just covering all the bases.^ you need to have new uni's to balance them properly. Worth asking the question I suppose.
Edited by surfmaster, 30 December 2006 - 09:48 PM.
#10
_2wild4u_
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Posted 30 December 2006 - 09:51 PM
as for the whining, what ratios are in the diff, i have been told the higher the ratio, the louder the whine will be????????????????/
#11
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Posted 30 December 2006 - 09:59 PM
wow, talk about quick replys, thx heaps guys, thx for the pic too, great job.
ok, first thing, yes it is a brand new uni, and i pretty much triple checked it was sitting properly. there is no way i would go cheap on something like that.
the second and main problem, is that i live at the sunshine coast in queensland and it has become very hard to deal with this guy in melbourne. i rang him up and told him about the problems i am having and he pretty much told me that every diff he makes is perfect and that it must be something i did wrong, and so i told him to go f*ck himself, and unless i take him to court im pretty much on my own to figure this one out.
ive done over 1000km on the diff now, put new oil in it at 700km (the hard facing comes off the gears) but this changed nothing.
i will look into the bent axle suggestion.
as for the tailshaft to diff angle it sounds like this can be a major cause of hassles, and at this point in time is looking to be the culprit, even if the angle is small. is it possible to buy adjustible trailing arms so i could change the angle of my diff?
oh, and im running 3.36 gears, ive heard these are meant to be a good ratio, is this right?
ok, first thing, yes it is a brand new uni, and i pretty much triple checked it was sitting properly. there is no way i would go cheap on something like that.
the second and main problem, is that i live at the sunshine coast in queensland and it has become very hard to deal with this guy in melbourne. i rang him up and told him about the problems i am having and he pretty much told me that every diff he makes is perfect and that it must be something i did wrong, and so i told him to go f*ck himself, and unless i take him to court im pretty much on my own to figure this one out.
ive done over 1000km on the diff now, put new oil in it at 700km (the hard facing comes off the gears) but this changed nothing.
i will look into the bent axle suggestion.
as for the tailshaft to diff angle it sounds like this can be a major cause of hassles, and at this point in time is looking to be the culprit, even if the angle is small. is it possible to buy adjustible trailing arms so i could change the angle of my diff?
oh, and im running 3.36 gears, ive heard these are meant to be a good ratio, is this right?
Edited by raceme, 30 December 2006 - 09:59 PM.
#12
surfmaster
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Posted 30 December 2006 - 10:06 PM
Are both unis new?
#13
_raceme_
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Posted 30 December 2006 - 10:13 PM
yes, i bought 2 brand new uni's when i got the tailshaft balanced. i also forgot to mention that the uni at the diff end is starting to show chatter marks on the shiny surface that the bearings run on, which definately shows that i have a vibration problem
#14
surfmaster
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Posted 30 December 2006 - 10:19 PM
Do you have a photo of the marks - daytime of course!!!
#15
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Posted 31 December 2006 - 01:06 AM
This is just an assumption but I would reckon that the velocity fluctuations occuring in the gearbox uni would be amplified over the length of the tailshaft causing the premature wear in your rear uni and may also explain your whine as it would be putting undue load on your pinion bearings.yes, i bought 2 brand new uni's when i got the tailshaft balanced. i also forgot to mention that the uni at the diff end is starting to show chatter marks on the shiny surface that the bearings run on, which definately shows that i have a vibration problem
Imagine this: there are V/F's happening at the gearbox uni, over the length of the tailshaft, this is causing a "whip" at the rear uni. In other words the tailshaft doesn't want to spin on its axis at the diff end. Result? Worn rear uni, possibly worn pinion bearings? and pinion and crown wheel mesh alignment issue while driving?
Edited by rodomo, 31 December 2006 - 01:16 AM.
#16
_The Baron_
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Posted 31 December 2006 - 09:42 AM
One from the left field.
A mate had a vibration in his A9X that we put down to a tailshaft thing (had it balanced) but it turned out to be the passenger side engine mount was broken.
You have also changed the bushes to a type that is renown to transmit noise into the car.
Can you put back the old drive train and prove the new diff setup is the cause?
You could also compare diff angles with a mates stocker.
There must be a diff place in the state that can have a look for you.
It always amazes me that anything reconditioned is expected to have run in noises when there was no such thing when it was new. Is it not new again, so why the noise?
Just another thought. My LX has 2 different sets of bolt holes for the lower arms where they bolt up at the body end. Have you gone the wrong hole. This will have a big impact on the pinion angle.
Just my 2 cents worth.
Cheers
A mate had a vibration in his A9X that we put down to a tailshaft thing (had it balanced) but it turned out to be the passenger side engine mount was broken.
You have also changed the bushes to a type that is renown to transmit noise into the car.
Can you put back the old drive train and prove the new diff setup is the cause?
You could also compare diff angles with a mates stocker.
There must be a diff place in the state that can have a look for you.
It always amazes me that anything reconditioned is expected to have run in noises when there was no such thing when it was new. Is it not new again, so why the noise?
Just another thought. My LX has 2 different sets of bolt holes for the lower arms where they bolt up at the body end. Have you gone the wrong hole. This will have a big impact on the pinion angle.
Just my 2 cents worth.
Cheers
#17
_raceme_
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Posted 31 December 2006 - 09:56 AM
unfortunately i am also running a t5 gearbox so it is not as easy as putting in a banjo and using another tailshaft. all i do know though is with the banjo everything was beautiful (except for the backlash and the fact that i could break them with ease) and with this new diff, im getting nothing but trouble.
will go out and check the mounting holes at the front of the lower trailing arms
will also try and take pic of diff angle, gearbox angle and worn uni.
i also know that the new rubbers cause hassles but they way i see it is that they can only help transmit vibration through to the car, they cant make it worse.
anyway, thx for the input guys.
i think i will also try and talk to a diff specialist after the christmas holidays.
will go out and check the mounting holes at the front of the lower trailing arms
will also try and take pic of diff angle, gearbox angle and worn uni.
i also know that the new rubbers cause hassles but they way i see it is that they can only help transmit vibration through to the car, they cant make it worse.
anyway, thx for the input guys.
i think i will also try and talk to a diff specialist after the christmas holidays.
#18
ls2lxhatch
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Posted 31 December 2006 - 11:44 AM
McDonald Bros Racing make adjustable upper trailing arms $295 and stronger replacement lower arms $255 including bushes.
http://www.mcdonaldb.../upperarms.html
http://www.mcdonaldb...lowertrail.html
I purchased both for my 9" but have not fitted them yet. If you have a LX then specify that you want the sway bar mounts fitted on the lower arms 10mm closer to the diff to provide extra clearance between the sway bar and the 9". If you do not ask for sway bar mounts then they will not be fitted.
You could try putting some weight in the back of the car to see if it makes any difference.
I have also read in this forum that some brands of 9" gears are noisier than others. From memory the ford gears are the quietest.
http://www.mcdonaldb.../upperarms.html
http://www.mcdonaldb...lowertrail.html
I purchased both for my 9" but have not fitted them yet. If you have a LX then specify that you want the sway bar mounts fitted on the lower arms 10mm closer to the diff to provide extra clearance between the sway bar and the 9". If you do not ask for sway bar mounts then they will not be fitted.
You could try putting some weight in the back of the car to see if it makes any difference.
I have also read in this forum that some brands of 9" gears are noisier than others. From memory the ford gears are the quietest.
#19
_Yella SLuR_
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Posted 31 December 2006 - 02:05 PM
Bent axles shagged out the bearings and marked them bit like you describe. Grab a dial indicator and measure the runout.
#20
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Posted 31 December 2006 - 03:13 PM
This is unrelated to your new diff, but I would suggest checking that your gearbox (rubber) mount is still ok. If the rubber is worn or broken then you will experience this kind of vibration.
Sometimes unrelated problems occur at the same time as changing something else. This happened to me. My gearbox mount was shagged, and I tried absolutely everything to fix it. I ended up changing everything and it wasn't until I finally pulled the trans out that I noticed that it was the problem!
Sometimes unrelated problems occur at the same time as changing something else. This happened to me. My gearbox mount was shagged, and I tried absolutely everything to fix it. I ended up changing everything and it wasn't until I finally pulled the trans out that I noticed that it was the problem!
#21
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Posted 31 December 2006 - 05:38 PM
I had 3 different reconditioned 9" centres in my car and was really dissapointed when they each had a bit of a whine, I changed my back tires and - voi la! quiet as - the Pirelli tires I had made a noise just like a diff whine.
M@
M@
#22
_devilsadvocate_
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Posted 31 December 2006 - 06:16 PM
Hi there, all good advice ^, the link provided by DocDamage would seem to provide all the specs and info needed to check the angles of the shafts to establish/eliminate whether its the prob. Have these angles been checked on your setup with spirit level inclinometers, or some other method?
A nice graph showing the variation in angular speed of the two sides of a uni versus degrees of rotation for several different values of input/output angle can be seen at, only for those who are interested.
You mention that the prob is worse under load, this could change the shaft angles if any of your engine/gearbox mounts are dodgy.
Im assuming the vibration appears at and beyond a certain speed? Does it stay there if you put the car into neutral and coast, does it became worse when loading the driveline in the opposite direction, ie when slowing down in gear.
One thing Id recommend is for both unis to be reinstalled and particularly attention to whatever is done when fitting them.......Ive had new unis fitted on several occasions by workshops to cars and vibration probs have appeared. They have just reinstalled them and prob gone.
A nice graph showing the variation in angular speed of the two sides of a uni versus degrees of rotation for several different values of input/output angle can be seen at, only for those who are interested.
You mention that the prob is worse under load, this could change the shaft angles if any of your engine/gearbox mounts are dodgy.
Im assuming the vibration appears at and beyond a certain speed? Does it stay there if you put the car into neutral and coast, does it became worse when loading the driveline in the opposite direction, ie when slowing down in gear.
One thing Id recommend is for both unis to be reinstalled and particularly attention to whatever is done when fitting them.......Ive had new unis fitted on several occasions by workshops to cars and vibration probs have appeared. They have just reinstalled them and prob gone.
Edited by devilsadvocate, 31 December 2006 - 06:17 PM.
#23
_raceme_
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Posted 01 January 2007 - 07:40 PM
unfortunately i have to go back to work tomorrow and so i will not get to work on my car for a week or so, will keep you updated when i get a chance to work on the car.
btw. i put brand new engine mounts and gearbox mount on the car only about a month ago, but i did check them anyway and they were perfect. the vibration is worse under load, by this i mean acceleration, and when u decelerate.
quoted by yellowslur "Grab a dial indicator and measure the runout" i dont really know wat u mean mate?? but will take the axles out when i get a chance.
btw. i put brand new engine mounts and gearbox mount on the car only about a month ago, but i did check them anyway and they were perfect. the vibration is worse under load, by this i mean acceleration, and when u decelerate.
quoted by yellowslur "Grab a dial indicator and measure the runout" i dont really know wat u mean mate?? but will take the axles out when i get a chance.
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