E12 Project help needed - e28 rear end swap

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Re: E12 Project help needed - e28 rear end swap

Post by TernandoFoledo » Wed Mar 06, 2019 9:14 am

Lock, actually the e34 are ""common"" here, the real pain are the e28 parts.
Knowing this, that the e34 is a direct fit to the e28 subframe, will help. I will check if the drum rear is still available to try to do this.

Now, if i cant get it, i will have to go creative, and think about adapting something. Like, if I was to get a set of wilwoods or brembos, wouldnt it just be putting a bracket there to place the caliper and setting everything up?

Never done brakes, so I might sound stupid, sorry about that haha

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Re: E12 Project help needed - e28 rear end swap

Post by TernandoFoledo » Wed Mar 06, 2019 9:51 am

Dimitrov wrote:
Fri Mar 01, 2019 9:01 am
onovakind67 has described everything very well and it will work for E12 also. I did such swap some years ago.
I addition i may say that the thickness of the drfiveshafts of E28 vary depending on which engine the car was equiped. You'd better go for subframe from m30 car. They are all with thicker driveshafts and have disc brakes (i am from Europe and here most of e28s have drums).
On my car i installed antisway bar from E28. To do this i needed to weld 2 mounting points on the bottom side ot the trunk. I just cut them from E28 and welded them on the exact same place on E12. Unfortunately i don't have any pictures of these. IF you decide to go for e28 antisway bar, keep in mind that they are also 2 types depending on the cover of the differential.
There is one more very good "PLUS" when you go for e28 rear axle - you got the diff with hall-sensor speedometer. So you can easily make your speedometer working with the newer engine and gearbox. I used e28 speedometer gauge and installed it on the place of the original E12 one - you can not notice that it is from another car. Fits perfectly! And you need only 3 wires to connect it. I may have pictures of this, i will search later.
Dimitrov, so looking for what you and onova said, its pretty straight forward, right? All the other mounting points and stuff are the same?

I've checked with the guy who has an E28 and its a 524d, with drums in the back. Its the only one I saw here in Brazil, at all, actually.

Its just pull off the old one, check the mounting of the Diff and mount everything up again? Something like that? Obviously taking the precautions that both of you mentioned.

I will also get the e34 arms with disks to make it happen as well right off the bat, if I manage to get everything.

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Re: E12 Project help needed - e28 rear end swap

Post by billy bee » Tue Aug 20, 2019 10:08 pm

onovakind67 wrote:
Sun Feb 24, 2019 9:38 am
I put an E28 rear axle in my E3, and the problems you might incur should be common.
1. As mentioned earlier, you will need the differential cover from an early E28 with the centered mount. It will bolt right on to the stock mounting point. Otherwise you will be fabricating an adapter.
2. You will need to re-route the brake lines to match up.
3. The sway bar mounting points are different. I welded a bracket onto the E28 arms to replicate the original mounting point.
4. The emergency brake cable sheath lengths were different so I made some extenders and couplers to make them match
5. The E28 shocks and springs bolted right up in the stock holes. I originally used the E3 top mounts but found that the E28 top mounts also work and are less complicated. The Bilsteins for the application have the adjustable spring perch, so you will have a few inches of adjustment in the height of the rear of the car. I also found that performance springs for E28's are much easier to find than older versions.

The differential uses a case common to the E23, E24, E28 and E30 so different gear ratios are available and easy to swap. E28's mostly have 3.25:1 ratios, so if you want to swap in a different ratio like the 3.45's from an E23 or 3.73's from an E30 you simply pop out the axle drive flanges from the E28 and install them in the new center section. LSD carriers are fairly easy to come by.
Sorry to hijack this thread, but this is the best information I've found from somebody who actually did the swap. (There's lots of conjecture out there.)

We are swapping a 1985 E28 rear subframe into a 1981 E12-based E24. We got the subframe for free and is comes with a diff, although not the correct cover. We are hoping to get some more information about the many little niggles you mention here. Is there a write-up anywhere? Maybe I'll have to do the write-up...

Also, when we are done, we will have a side-loader diff for sale. It needs new bearings and seals but both the ring and pinion gears look excellent. Car has about 125k on it. I can provide pictures.


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Re: E12 Project help needed - e28 rear end swap

Post by Lock » Wed Aug 21, 2019 1:41 am

I'm also going to do this conversion after I install Motronic. I have a e28 subframe, e34 trailing arms and brakes, LSD center and pieces.
What I can say is the center diff mount with cover is the easiest way to mount the diff if you can find the cover, but it's also the weakest - the e12 diff mount is a weak point especially if you're going to make some power. There's a FAQ about mounting a plate in the trunk though which helps. I'm planning on getting a Z3 diff and a Garagistic secondary diff mount kit and bolt that in for better support.
I considered using an e34 subframe (which braces the diff against twisting on the sides and uses the rear mount as a subframe support) but you'd have to cut and weld the ends to shorten it, it's been done but I don't think it's worth it. Especially when Garagistic still sell adjustable powdercoated e28 subframes with a core, and the e28 subframe is essentially the same part.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

billy bee
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Re: E12 Project help needed - e28 rear end swap

Post by billy bee » Tue Sep 03, 2019 5:21 pm

TernandoFoledo wrote:
Sun Dec 16, 2018 9:59 am
PS: Since I started this research, an E28 rear (without shocks) appeared to me. I'm still trying to negotiate, and check if it would be "doable", since I have to import a whole rear end and might cost a fortune. The e28 rear is just just plug and play? Does it need a lot of adaptations?
It's do-able. We just got it done. I posted it up here and on BigCoupe.com. We swapped an E28 rear subframe into a 1981 E12-based E24 633CSi. It went smoothly and should not cost too much. We did it for about $20. plus some materials we had kicking around the shop. Not easy, but completely do-able.

Feel free to PM me if you have any questions. Happy to help.


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Re: E12 Project help needed - e28 rear end swap

Post by TernandoFoledo » Wed Oct 23, 2019 3:19 pm

Hey everyone, just wanted to give a return here!

After many research, time and all spent, we came to a solution.

The E28 rear swap was a 'no go'. The only one available was too expensive, due to the fact that as I mentioned earlier, here in Brazil we simply dont have these generations (E12, 24 and 28).

We then moved to the E36 swap idea, which was the most wanted and seemed to work in 2002's and some E12s that I saw. But there was a huge error in the projects we saw - even the ones sold pre-made by some folks - that could compromise the security of the car. Basically, it takes off a lot of 'fixing points' of the E12 rear end layout.

Then we came to the only last solution: a new crown set to the original diff.

We found a 3.45 ration, which was the one I was looking for, and got it shipped.

Now I'm considering reinforcing the diff mount spot, since its a known weak point.

Thanks a lot for everyone that helped and, if possible, lets share our discoveries here to help others :)


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