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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sat, Dec-16-2017, 12:54:43 AM   #31
Braymond141
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Default Re: Adjusting Diff backlash

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Originally Posted by TheCoder View Post
I just drove another M3 today, and it didnt have that clunk. So the plan is to chase this issue until it's fixed. I have to take nowaker's side here, this clunk is not normal.

I just noticed my flex disc needs to be replaced, so ill do that along with tranny bushings and centering sleeve. I dont suspect it will fix the clunk, but might mitigate it. If it doesnt, then it will be time to open the diff and figure out if its my ring and pinion or the spider gears. If its the spider gears, then Ill just get a new lsd unit.

Back to the original question, and assuming i do find excessive backlash (pinion and ring) , does anyone have any additional advice regarding the specific process of setting yhe backlash back to spec ?

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THE CLUNK IS NORMAL. However, there are things you can do to mitigate just how bad it is... and in some cases never hear it at all.

Maintenance, maintenance, maintenance...

*Driveshaft. Fresh Giubo, Fresh CSB. Is the u-joint still good? Did you pre-load the CSB?
*Engine and Trans. Fresh motor mounts, fresh trans mounts.
*Rear axle. Is your subframe tearing? Fresh differential cover bushings, fresh front differential bushing. Differential bolts tight? Subframe bushings if applicable. Some also indicate fresh output flange circlips help for a time. Some have also found their input flange on the passenger side popped out.
Lastly. Are you driving your manual transmission correctly? Your use of the clutch will determine the number of occurrences.

The easy stuff listed above, INSTALLED RIGHT, will pretty much guarantee no clunking.

You're not going to turn this into a debate because there is no debate to be had. The issue is there and it is "normal". You keep readdressing it like the opposite is true. Sorry, it just isn't. The differential design is the issue. Some rebuilders will correct it by addressing the spider gear setup but you shouldn't have to if everything else is addressed properly. I don't think anyone has released any data on how to go about correcting it either.

At 160k miles my 02 had a super floppy passenger output flange and no noise because all of the maintenance was done. I could get it to clunk with careless clutch use (really no different than any other M car with equal length output flanges though).

(that all said, if your input flange has been removed and improperly reattached, then yes you have a totally different issue and clunk)

Last edited by Braymond141; Sat, Dec-16-2017 at 04:56:37 PM.
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Old Sat, Dec-16-2017, 01:34:37 AM   #32
TheCoder
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Default Re: Adjusting Diff backlash

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Originally Posted by Braymond141 View Post
*Driveshaft. Fresh Giubo, Fresh CSB. Is the u-joint still good? Did you pre-load the CSB?
Except for the Guibo, everything else is fresh and CSB was properly preloaded. I got plans for the Guibo this Christmas.


Quote:
Originally Posted by Braymond141 View Post
*Engine and Trans. Fresh motor mounts, fresh trans mounts.
I didn't notice the Trans mounts splitting , but I already have RE mounts to replace the existing ones. I'll replace the Trans mounts when I swap the Guibo.

I didn't change the engine mounts, kept that for my front suspension refresh project.


Quote:
Originally Posted by Braymond141 View Post
*Rear axle. Is your subframe tearing? Fresh differential cover bushings, fresh front differential bushing. Differential bolts tight? Subframe bushings if applicable. Some also indicate fresh output flange circlips help for a time. Some have also found their input flange on the passenger side popped out.
I refreshed the entire rear suspension. New AKG bushings, new seals, Reinforced subframe by welding plates + Vince bar. All seals of carious Diff output/input flanges were replaced.

Quote:
Originally Posted by Braymond141 View Post
Lastly. Are you driving your manual transmission correctly? Your use of the clutch will determine the number of occurrences.
If you're asking if I ease my clutch into gear or just drop the clutch like a rock, then it's the former. However, I dropped it like a rock with the other m3 I drove this morning, and didn't observe a 'clunk' from the rear of the driveshaft.


Quote:
Originally Posted by Braymond141 View Post
You're not going to turn this into a debate because there is no debate to be had.
I think it already turned into one...
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Old Sat, Dec-16-2017, 01:37:57 AM   #33
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Default Re: Adjusting Diff backlash

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Originally Posted by schoonerm3 View Post

Then there is a 3rd possiblity and will only come into play after a diff seal job. When doing the input pinion seal. There is a technique to doing it and making sure the pinion nut is replaced with exactly the same amount of torque to achieve exactly the same amount of preload. Well I did an experiment . I did the seal on my 3.62 which was previously quiet as a mouse. I marked the nut 2 different places and counted the turns yada yada . But before I did this I measured the break away torque using an inch pound torque wrench and measured my overall rotational torque ( no side shafts attached) at 25in/lbs. I then put it back together and put the nut on exactly as it came off but I did not check the rotational torque. Put it together and drive it. I had a mild increase in clunk. Back on the lift and disconnected the shafts and measured the rotational torque. It was only 12in/lbs. So I tightened the preload back to 25 in/lbs and it was back to normal..
This is indeed what I am concerned about! because I did change the input seal. Sadly, I didn't measure the rotational torque before and after, but I turned the nut back to the exact position as it was previously.

Thanks
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Old Sat, Dec-16-2017, 01:39:48 AM   #34
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Default Re: Adjusting Diff backlash

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I wouldn't recommend DIY diff work. If you search here, there are some good writeups about it. I did mine out of pride, and it sucked from start to finish.
Find a diff shop that's familiar with these, worth the $$. BMW makes some of the parts difficult to get and painful to buy!
Internal parts for the carrier (where the play is likely to be found!) are NOT available from BMW.
Blanton Performance Gearing
Diffs Online
Turner
Bimmer World
Sure there are others that are worthwhile!
Thank you. if I confirm the play is at the spider gears, then I'm getting another diff from one of the shops you recommended. I'll try my luck with the ring and pinion backlash though.
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Old Sat, Dec-16-2017, 01:59:03 AM   #35
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Default Re: Adjusting Diff backlash

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Originally Posted by TheCoder View Post
Except for the Guibo, everything else is fresh and CSB was properly preloaded. I got plans for the Guibo this Christmas.



I didn't notice the Trans mounts splitting , but I already have RE mounts to replace the existing ones. I'll replace the Trans mounts when I swap the Guibo.

I didn't change the engine mounts, kept that for my front suspension refresh project.



I refreshed the entire rear suspension. New AKG bushings, new seals, Reinforced subframe by welding plates + Vince bar. All seals of carious Diff output/input flanges were replaced.



If you're asking if I ease my clutch into gear or just drop the clutch like a rock, then it's the former. However, I dropped it like a rock with the other m3 I drove this morning, and didn't observe a 'clunk' from the rear of the driveshaft.




I think it already turned into one...
Giubo (jew-boh), not guibo.

AKG components are going to make the issue worse as you're eliminating the OEM rubber bushing dampeners. I've come to learn that "upgrades" such as this are not upgrades at all. Having been down the AKG route for a street car, it was a real annoyance to undo it.
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Old Sat, Dec-16-2017, 02:05:08 AM   #36
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Default Re: Adjusting Diff backlash

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Originally Posted by Braymond141 View Post
Giubo (jew-boh), not guibo.

AKG components are going to make the issue worse as you're eliminating the OEM rubber bushing dampeners. I've come to learn that "upgrades" such as this are not upgrades at all. Having been down the AKG route for a street car, it was a real annoyance to undo it.
Thanks for the correction

About AKG bushings, they were applied only to the subframe and not the diff. I don't really have a choice since the BMW subframe bushings contribute to the infamous floor crack. I do though have a a poly bushing for the front diff mount, and I think I'll swap it back to OEM.
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Old Sat, Dec-16-2017, 02:08:50 AM   #37
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Default Re: Adjusting Diff backlash

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Originally Posted by TheCoder View Post
Thanks for the correction

About AKG bushings, they were applied only to the subframe and not the diff. I don't really have a choice since the BMW subframe bushings contribute to the infamous floor crack. I do though have a a poly bushing for the front diff mount, and I think I'll swap it back to OEM.
Totally understandable in that regard. I did subframe and diff which ended up being a terrible choice You might have better results with your setup.
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Old Sat, Dec-16-2017, 07:54:06 AM   #38
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Default Re: Adjusting Diff backlash

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Originally Posted by Braymond141 View Post
Some rebuilders will correct it by addressing the spider gear setup (ramp angle changes?) but you shouldn't have to if everything else is addressed properly. I don't think anyone has released any data on how to go about correcting it either
M variable lsd does not have ramp angles. High viscosity pump is used instead.

A guy in the UK can shim the spider gear and has remanufactured the clutches but he is the only one and keeps it very low profile. No one else doing this as of yet.

As extra information. I have poly subframe bushes and OEM diff. No noise. But when I had poly diff I will could head some drive line noises. Took the poly diff out and noise gone. So from that conclusion poly subframe won't be an issue.
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Old Sat, Dec-16-2017, 04:01:06 PM   #39
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Default Re: Adjusting Diff backlash

^^ I had a long conversation with Jim Blanton when I was doing mine. I expect he has a solution for the spider gear backlash.
How about a DIY solution... with feeler gauge, measure the clearance between the spiders and the case. Make an appropriate shim out of stainless shim stock. It would need to conform to whatever shape the back of the spider gear is...
If I had all the time in the world (and actually gave a sh*t), I would totally try that out!
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Old Sat, Dec-16-2017, 07:04:11 PM   #40
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Default Re: Adjusting Diff backlash

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Originally Posted by nowanker View Post
^^ I had a long conversation with Jim Blanton when I was doing mine. I expect he has a solution for the spider gear backlash.
How about a DIY solution... with feeler gauge, measure the clearance between the spiders and the case. Make an appropriate shim out of stainless shim stock. It would need to conform to whatever shape the back of the spider gear is...
If I had all the time in the world (and actually gave a sh*t), I would totally try that out!
Could be done. Spider gear back is a rounded shape.
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Discussing Adjusting Diff backlash in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)