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      09-16-2022, 05:55 PM   #1
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Setting the suspension bushings to neutral

l have the rear suspension removed from the car but I haven't loosened any of the control arms yet.
The upper and lower wishbones/control arms are at a different height on the left side of the car compared to right side.
I could mark and measure the different angles and try to recreate them when reassembling but that is really not the best way.
The real problem is tightening the inner bolts on the rear diff carrier, there is just no room to get at those nuts.
How are others tackling this?

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      09-17-2022, 04:12 PM   #2
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haven't done this myself yet... just speculating on what you were saying...

assemble it without the diff, tighten the bolts and then put the diff in?
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      09-17-2022, 06:06 PM   #3
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Quote:
Originally Posted by vt100 View Post
haven't done this myself yet... just speculating on what you were saying...

assemble it without the diff, tighten the bolts and then put the diff in?
Yeah I see what you are saying, but the weight of the diff is integral to getting the proper ride height adjustment.
I guess I could do it your way and load the diff into the back behind the seats, that should be fun
Thanks
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      09-17-2022, 09:12 PM   #4
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The bolts can be accessed by moving the diff back as far as it will go. It doesn’t need to come out. You could also replicate the weight with the diff or a bag of sand in the trunk. Using spherical bearings instead of rubber also mitigates this issue, but I wouldn’t do this in a street car.

IIRC, my old E39 M5 called for 4 people, or equivalent weight, in the car when tightening front control arms for this same reason. So I would think you want weight in the seats as well with rubber bushings.
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      09-17-2022, 09:35 PM   #5
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Quote:
Originally Posted by Michael9218 View Post
The bolts can be accessed by moving the diff back as far as it will go. It doesn’t need to come out. You could also replicate the weight with the diff or a bag of sand in the trunk. Using spherical bearings instead of rubber also mitigates this issue, but I wouldn’t do this in a street car.

IIRC, my old E39 M5 called for 4 people, or equivalent weight, in the car when tightening front control arms for this same reason. So I would think you want weight in the seats as well with rubber bushings.
Sure, makes sense. Let the cradle take the weight while tightening the bolts then slide the diff forward again and lock it down.
I have a 120lb anvil and few old flywheels that I throw into the D/S foot well to simulate my weight.
Thank you
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      09-19-2022, 03:30 PM   #6
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Build a crude jig to mark the locations and put the new ones back in the same orientation. A few pieces of wood should do it.
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      09-20-2022, 05:36 PM   #7
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It yourself some (2) camping/RV water containers… 5 gal ones or similar size should work. You can add water to get the appropriate weight required to make adjustments. Place in trunk….

This is the method BMW uses I believe when doing an alignment (I think in drivers seat in this case)… which is why I had mine done by BMW vice a chain or other independent. Makes sense to weight the car down appropriately if you think about it….
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      09-21-2022, 05:04 AM   #8
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Not sure I see the issue here.

When tightened, the lower control arms and spring perch to subframe bolts shouldn't make the connection totally rigid.

There should still be an element of vertical movement. In fact, there must be because if there weren't then the rear suspension would be completely solid. When you lower the vehicle and go for a drive after tightening everything the suspension should settle to where it should be.
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      09-21-2022, 06:19 AM   #9
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Quote:
Originally Posted by ANILE8 View Post
Not sure I see the issue here.

When tightened, the lower control arms and spring perch to subframe bolts shouldn't make the connection totally rigid.
The center sleeve in the bushing is rigid to the subframe but the rubber of the bushing allows the movement of the spring perch and LCA.
If that inner sleeve is tightened in any other position than with the full weight on the car on it the spring of the rubber will always be trying to get back to its neutral position, that will wear out the bushing prematurely.
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      09-21-2022, 07:50 PM   #10
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Quote:
Originally Posted by grannyknot View Post
The center sleeve in the bushing is rigid to the subframe but the rubber of the bushing allows the movement of the spring perch and LCA.
If that inner sleeve is tightened in any other position than with the full weight on the car on it the spring of the rubber will always be trying to get back to its neutral position, that will wear out the bushing prematurely.
I see, I thought the rubber bushing would still be able to move. Seems like a PITA problem and another reason to ditch the stock bushings. Why are you removing them, are they needing to be replaced? How many miles on the vehicle?

Sorry, in that case, I don't know how you are going to install them that way. When I did mine I just used adjustable camber arms that have monoballs, not bushings and monoballs on the upper inner control arm also. Then you won't have this problem and you will also get better performance if you are going to change them out anyway you might as well go for an upgrade. I replaced mine because I don't like rubber bushings not because they were worn. The benefit you get is zero deflection.



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      09-21-2022, 08:54 PM   #11
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Quote:
Originally Posted by ANILE8 View Post
I see, I thought the rubber bushing would still be able to move. Seems like a PITA problem and another reason to ditch the stock bushings. Why are you removing them, are they needing to be replaced? How many miles on the vehicle?

Sorry, in that case, I don't know how you are going to install them that way. When I did mine I just used adjustable camber arms that have monoballs, not bushings and monoballs on the upper inner control arm also. Then you won't have this problem and you will also get better performance if you are going to change them out anyway you might as well go for an upgrade. I replaced mine because I don't like rubber bushings not because they were worn. The benefit you get is zero deflection.
I'm replacing all rubber bushings in the car, it has 91,000mi at the moment so time for a complete refresh.
Once I get it back together I will jack up the car and rest the tires on 4 one foot blocks of wood so that the whole weight is on all bushings then climb under and tighten everything.

There are some benefits to solid bushings as you say but also draw backs, noise, vibration, harshness.
All the fun cars I have owned for the past 30 odd yrs have had poly and solid mounts/bushings.
Great for the track, tolerable for a young guy on the street but I have hit the age where I'm done with that.
I still want a powerful car that handles well but with a bit more comfort.

Besides, fresh rubber bushings are a lot crisper than 14 yr old rubber with 91,000mi on them.
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      09-21-2022, 10:14 PM   #12
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Are you sure you can't reach the bolts when the diff is in?
TIS says that you only have to remove the drive axles and then you can reach the bolts.

I've fitted polyurethane bushings, these don't have this problem as they act as a bearing, not a bushing.
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      10-29-2022, 04:45 PM   #13
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Quote:
Originally Posted by GuidoK View Post
Are you sure you can't reach the bolts when the diff is in?
TIS says that you only have to remove the drive axles and then you can reach the bolts.
So got the whole assembled carrier back up in the car today and you can see the passenger won't be a problem but the driver side I think I'll have to push the diff back an inch or so to get a torque wrench in there.
They did it at the factory so one way or the other I'll get it done.
Thanks for help.

Passenger side looking forward
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Driver side looking straight up,
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      10-29-2022, 07:09 PM   #14
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My info from TIS wasn't 100% complete. TIS indeed says to replace the upper left one, the diff has to come out.
For the lower left one, loosening it from the propshaft seems to be enough apparently.
TIS says for the right ones, only the driveshaft has to be disconnected. (left and right have separate entries).
I only have a dutch version here otherwise I could make a printout.

You also can't get an angled ringratchet on the upper bolt?
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Last edited by GuidoK; 10-29-2022 at 07:14 PM..
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      01-14-2023, 09:08 AM   #15
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Quote:
Originally Posted by ANILE8 View Post
I see, I thought the rubber bushing would still be able to move. Seems like a PITA problem and another reason to ditch the stock bushings. Why are you removing them, are they needing to be replaced? How many miles on the vehicle?

Sorry, in that case, I don't know how you are going to install them that way. When I did mine I just used adjustable camber arms that have monoballs, not bushings and monoballs on the upper inner control arm also. Then you won't have this problem and you will also get better performance if you are going to change them out anyway you might as well go for an upgrade. I replaced mine because I don't like rubber bushings not because they were worn. The benefit you get is zero deflection.



When you used these
Turner Race Monoball Rear Control Arm Upper Inner Bushing Set - E36/E46/X3/Z4 did you get any rattling and excessive NVH from these bushings ? Getting ready to change out the Subframe and Diff bushings. Are the Monoballs sealed in these ?

Thanks
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