Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 spec

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Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 spec

Post by Juvvajuvva » Wed 25 Jan, 2017 01:37

Hi,
I just wondered if anyone can help on this please.
I am basically attempting to put z3 1.9 trailing arms on a 2.8 in order to get wider rims on the back.
These have been braced in two places.
Obviously I will have to use shorter drive shafts,either 1.9 CV drive shafts or Z3M ones.
The diff output flanges are different on the 2.8 to 1.9 and Z3M.
The small case flanges (1.9) are shorter than the 2.8's so I guess I need medium case ( to get the length).

Are 80mm M8 stud diameter and 1.9 CV shafts too weak?
Nm torques are way different.

I am not sure of the different exact engths of the CV shafts.Anyone know?
I can find output shaft diameters and PCD's but not cv lengths.

I am not sure which output flanges I need to go from my medium case Euro Z3 2.8 diff.
Is there an alternative? E28 etc?
The originals are 86mm M10 but the half shafts will be too long from the 2.8 so they are a no go.
So I need half shafts that fit the 1.9 trailing arms,that are strong enough and the output flanges to match.
Does anyone know which output flanges and CV half shaft/axles I need and does anyone have any that they want to sell?
If anyone could help,that would be great.
PS I have done some extensive net searching and so far have not found a clear answer.
Kindest regards
Juvva.

spurs fan in a coupe
Joined: Fri 18 Apr, 2008 20:24
Posts: 1435

  Z3 coupe 2.8
Location: woking

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by spurs fan in a coupe » Wed 25 Jan, 2017 21:35

If you're local to Woking, Surrey, I might be able to help.

PM me if so.

Thanks
we expres: " He did hear the bells ringing, but doesnt know where where the clapper hangs".

Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Juvvajuvva » Thu 02 Feb, 2017 01:32

Has anyone actually done this conversion or is it a myth of chat?

Please let me know if you have and how you cracked it :-)

If no one has, I guess I will and develop a kit with Chromoly output shafts.
Anyone interested? :D

Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Juvvajuvva » Sun 05 Feb, 2017 11:15

Really! No one?

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Gazza
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Joined: Tue 04 Oct, 2005 21:58
Posts: 9165

  M roadster S54
Location: East London/Essex

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Gazza » Sun 05 Feb, 2017 12:27

It's a lot of effort to get a wider rim to fit.

As you suggest, torque figures are different on the 1.9 parts so I guess this may compromise the intended fitment on a 2.8

Easiest way as I see it, fit a complete 'M' spec rear that will handle the 2.8 torque specs or go for the complete lower spec 1.9 rear for availability.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

S54 M roadster Image Mustang Fastback, BMW Z1, BMW M3 CSL.

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Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Juvvajuvva » Sun 05 Feb, 2017 20:48

Hi Gazza,
Thanks for your reply. Do you have a Z3M rear end I can buy?
Regards
Juvva.

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Gazza
Site Admin
Joined: Tue 04 Oct, 2005 21:58
Posts: 9165

  M roadster S54
Location: East London/Essex

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Gazza » Mon 06 Feb, 2017 21:22

No I don't.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

S54 M roadster Image Mustang Fastback, BMW Z1, BMW M3 CSL.

ImageImage

deni2s
Joined: Mon 25 Mar, 2013 22:02
Posts: 745

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by deni2s » Tue 07 Feb, 2017 13:34

Funny thing is that on my yellow z3 2.8 one side is normal (wide) and the other side looks like from some 1.9 or compact. Using some spacer to make them a little bit less uneven. Don't know how that's exactly achieved (some cheap repair). But from what I understand, I need another trailing arm and driveshaft to fix that (probably not worth the effort).

Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Juvvajuvva » Tue 07 Feb, 2017 18:48

Which side?
I may have a 2.8 trailing arm if you want one.

The way to tell is to look at the carrier/hub section and look at the lower damper mount.
If it is 1.9 it will look considerably shorter than the other side,if that one is in fact 2.8.
:)

Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Juvvajuvva » Wed 08 Mar, 2017 23:04

I have successfully built a rear end with the track and strength of a Z3M with 1000hp drive shafts and diff
Output flanges! 10j rims fitted.
Very happy.

Dino D
Joined: Fri 10 Feb, 2012 16:59
Posts: 376

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Dino D » Thu 09 Mar, 2017 23:09

Juvvajuvva wrote:I have successfully built a rear end with the track and strength of a Z3M with 1000hp drive shafts and diff
Output flanges! 10j rims fitted.
Very happy.
Now that sounds interesting!
What was the cost, another mod yo add to the list I think!
Any pics?

Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 40

  Z3 roadster 2.8

Re: Z3 2.8 Rear end conversion, reducing 2.8 width to 1.9 sp

Post by Juvvajuvva » Fri 10 Mar, 2017 18:12

Are you interested in buying one or in the engineering?

As Z3M rear ends are rare as hens teeth I would like to make and sell them
But I don't think people would pay the money they cost.
It's a lot of man hours and the drive shafts are costly.

I have a remanufactured 2.8 rear end that is finnished with Powerflex bushes that
I am willing to part with.

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