2002 chassis measurements - rear differential mount position

[D.martijn]

Hey guys, 

 

So on my Touring project, I decided to replace the rear differential crossmember as there was quite a bit of rust hiding inside of this section. (diff carrier and boot floor)

I had bought the Restoration Design panel after asking them if it fitted both Touring and Sedan - they confirmed that it fitted both models.

Well turns out this is not true. (should have known better since both have a different part number but I didn't think any further... ohwell)

 

My plan is now to reproduce the rear differential panel for the Touring model (I already have interest from a German shop as well  )

However IF I do reproduce this panel, the shop prefers to have the mounts for the differential all ready welded, so a complete panel!

So I need to figure out where to place these mounts to have them correctly positioned.

 

 

Before removing our original diff carrier panel we checked it's locations from the rear subframe bolts like the BMW diagram.

However, as I now found out the measurements that BMW gives are measured diagonally NOT planar.  

(this thread)

 

We used plumb bobs to measure from the subframe bolts to the rear diff mounts. The strange thing is that we are able to match the measurement for the right side 674,5mm (measuring planar) with the measurement from BMW (non planar) both diff mounts are the correct distance apart (243mm) 

The left side is different.

 

 

 

I now put this all into Solidworks
For the measurements from BMW to work out, we need to space the differential 476mm towards the rear instead of 475mm

(there is a tolerance of +/-2mm so I worked with the 476mm)

 

 

Putting this into Solidworks, I'm able to calculate the PLANAR measurement that we need to measure.

Right  = 671,5mm
Left = 664,3mm

 

The PLANAR measurements we measured on the car

Right = 674,5mm

Left = 653mm

 

Since the differential is OFFSET from the center of the car to the left side 

For the measurements from BMW we measure

OFFSET TO THE LEFT = 5,08mm

 

OFFSET TO THE LEFT = 15,23mm

MORE FORWARD = 5,94mm  -> So our differential was positioned at 470mm from the rear subframe points.

 

I do plan on using a laser and measure more stuff on the car to see where we are wrong..

Measuring from the front subframe points to the rear subframe points we get the same measurements left to right so those are square from each other.

Car is also levelled left to right and front to back on the sills.

 

Anyone have some input/feedback for this?

 

Thanks!

 

Kind regards,

Martijn

 

Edited January 29 by D.martijn

[D.martijn]

Checking the panel from Restorations Design,

Both differential mounts are spaced right in the center of the panel (no offset taken into account)

As well as, the height seems to be off. 

 

Before removing our panel, we measured from the boot floor to the center of the holes 105mm 

The panel from Restoration Design has the hole at 100mm from the flange that sits onto the floor.

 

This flange section (boot section with the two rectangular indentations) is the same for the sedan and touring, as it's the same floor section that's connected to the front floor section

[D.martijn]

Anyone that could also measure their 2002??

[uai]

user @manimal has scans he could use

 

 

Edited January 30 by uai

[its55]

4 hours ago, D.martijn said:

Anyone that could also measure their 2002??

I could try - what measurement do you need?  My 02 is all together so I may not be able to get exactly what you need…

[D.martijn]

4 hours ago, uai said:

user @manimal has scans he could use

 

 

 

Thanks, I've contacted him if he could help me with some measurements.

 

4 hours ago, its55 said:

I could try - what measurement do you need?  My 02 is all together so I may not be able to get exactly what you need…

 

That would be awesome!

 

I would like to know what other people measure for the distance between the rear subframe points and differential.
Again, PLANAR or DIAGONALLY. (I find planar easier to measure since in my opinion it's also more accurate. than trying to bend your measuring tape)

 

As well as the height from the center of the differential mount bolt to to flange of the panel where it's spotwelded onto the floor. like so:

 

Thanks!!

 

[uai]

I‘ll try to when I‘m back from ice driving. 
Currently with the roof rack my Garage is too low to do it half comfortable.
I'll switch the diff back to 3,64 afterwards so I have space to measure when the diff is out.
So you'll have to wait - will be returning from Ice driving on on 10th Feb

Edited January 30 by uai

[D.martijn]

19 minutes ago, uai said:

I‘ll try to when I‘m back from ice driving. 
Currently with the roof rack my Garage is too low to do it half comfortable.
I'll switch the diff back to 3,64 afterwards so I have space to measure when the diff is out.
So you'll have to wait - will be returning from Ice driving on on 10th Feb

 

Thank you! I appreciate it very much!

[tzei]

You could easily fab something like this:

 

Champ Tram Gauge (non-calibrated) - 6000

WWW.AUTOBODYTOOLMART.COM

---

The Champ Tram Gauge is used to make point to point measurements. A point to point measurement is the shortest distance between any two reference points. In most cases, this is accomplished by setting a dimension on the Tram Gauge and comparing it to two...

 

So no bending of measuring tape. Add bubble level (digital if you wish)... well you'll get the

idea. 

 

is what i did anyways

[its55]

2 hours ago, D.martijn said:

 

Thanks, I've contacted him if he could help me with some measurements.

 

 

That would be awesome!

 

I would like to know what other people measure for the distance between the rear subframe points and differential.
Again, PLANAR or DIAGONALLY. (I find planar easier to measure since in my opinion it's also more accurate. than trying to bend your measuring tape)

 

As well as the height from the center of the differential mount bolt to to flange of the panel where it's spotwelded onto the floor. like so:

 

Thanks!!

 

 

so far I was able to get this on the differential. One measurement is at the front side of the bolt the other is at the rear.  sorry I don’t have a millimeter tape measure. Hopefully this will help.  

 

 

 

 

[D.martijn]

On 1/30/2024 at 8:27 PM, uai said:

I‘ll try to when I‘m back from ice driving. 
Currently with the roof rack my Garage is too low to do it half comfortable.
I'll switch the diff back to 3,64 afterwards so I have space to measure when the diff is out.
So you'll have to wait - will be returning from Ice driving on on 10th Feb

 

Hello Uai,

 

Would you be able to measure these distances when you have the time and the rear end is removed from the car like you mentioned.

 

I made a little diagram with some letters to make it more clear. Car should be levelled side to side and front to back on the rocker panels.

I placed a blump bob in the holes of the differential to measure to.

 

Measuring these distances level to the car (planar)

 

A = distance from center of hole in the brackets to floor (I measured 105mm)

 

B = distance from subframe bolt flange to floor or center hole diff (less needed this measurement)

 

C = distance between subframe bolts and plumb bobs (again less needed, I can calculate this with the other measurements)

 

D = distance between center of both subframe bolts

 

E = Distance between center of holes diff brackets

 

F G H I = distance center subframe bolts to plumb bob in diff brackets.