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Is there any company/ person who has fitted an e30 carrier into e21 beam that could offer this service?
Ive got a local guy whos willing to do it but i will have to pay for a jig and will need moch up parts etc
( located south coast of uk)

Can anyone confirm clearance for fiel tanks etc
Whis done this conversion?

The E30 rear is not the optimal trade if you ask me.

I know some guys from Norway who do it. First off you will still have to run the tiny itsy bitsy shafts from the E21. There is also a lot more cutting and welding involved as the sway arms needs to be modified (the E30 has not got coils in the rear) and the fuel tank / tanks (depending on the year of your car) will not fit and you will have to use a boot / trunk located fuel tank.

The only real upside to this build is that you can keep the narrow track of the E21 and you now have access to medium diff´s.

The E28 setup, if you can live with the slightly upped track (you can use E36 high offset wheels to keep the wheels under the car) is the perfect setup IMO. You get rear disc brakes (granted you can get that for the E30 too), you get the medium (or even the big) diff, you get driveshafts twice the diameter of the E21 ones, and you can keep the fuel tanks if your car is originally fitted with dual tanks (later models).

I was just going to use the centre of the e30 beam and graft in into the e21
Then use the e30 shafts ( i have 4 so was thinking of cutting and shutting 2 to make each shaft)

mcjjordan wrote:I was just going to use the centre of the e30 beam and graft in into the e21
Then use the e30 shafts ( i have 4 so was thinking of cutting and shutting 2 to make each shaft)

The E30 shafts don´t fit on the E21 sway arms. So you need to use the E30 ones wich you can´t because they are totally different.

E30 sway arm:



E21 sway arm:



As you can see the E21 is designed to take all of the pressure from a coil strut, where the E30 one is made to even the load out by having springs and dampers in seperate locations. Maybe they could be ok if you just bolted on the coils from the E21 (i really think that it would be ok) but there is no room as the E30 shock is mounted at the bottom of the wheel hub and also would give you a terrible ride height.

So you will need to use the E21 sway arm and then the E30 shafts wont fit, they are not the same length as the E21 ones.

It is possible, and i have seen pic´s of it done, but what you will end up with is basically a E21 frame with a 188mm diff. Everything else will still be E21 stuff.

I recommend that you set up your requirements for this project. What are you planning to achieve with this modification? Stronger shafts, stronger diff, rear disc brakes ? If your goal is just to get access to 188mm diffs then it is a great way to do it. If you want to beef everything up a bit, i´d reccommend doing the E28 swap instead.

I Am thinking you are talking about keeping your e21 beam and trailing arms and fitting the e30 diff carrier.

So you will just shorten a set of e30 axles fit mid case lsd and do skids?

I have read a old thread of a guy fitting a m50 and making this rear work. He was from the Nordic countries.

I have found this


I'm excited to see where this one leads. I lust after e21s on a daily basis.

I hope you have some magic up your sleeve for the diff. I grenaded two open diffs with a woken up m20b25 in my old e21. I imagine the s50 should do a bit more than the wheezing m20 ever thought possible.

I ended up making a franken-subframe of sorts. Combining the bottom half of the e21 subframe, and the top half of an e30 subframe so I could use the physically larger e30 diff. It wasn't particularly pretty (read: it was ugly as SIN and would have no place on a car like this), but it's still on the road. The secret ingredients to take up the extra width of the e30 diff is 2002 half-shafts and e30 CVs, they have the same splines and slip right together.