N62 Z3 Part 25: Rear End Refresh

Pretty straightforward at this point. I have the DunkelDiff™ draining

The subframe dropping

...and dropped

Awaiting parts at this point but that's fine as it will give me some time to make some decisions on a few things


I wanted to clean things up a little bit first and that starts with cleaning. I don't love the condition of all this stuff - more rust than I am used to seeing. Most the rust is on the subframe itself so I think I will replace it with a nicer one I have in storage

In fact the rust was so bad that when I removed the springs, part of it remained on the subframe stuck on the spring pad. I have never seen this on a Z3 before. I was eventually able to wrestle it off and get the broken piece of spring out

A local Z3 enthusiast - thanks Brad - brought me some good condition springs! Thanks Brad!

My solid subframe bushings arrived from Turner and it does seem to me they are designed for E30's more than Z3's. The AKG poly bushings are listed specifically for Z3's and 318ti's and they have a different bushing available for E30's. The critical difference is that the Z3 poly bushings have "pockets" on the top of the bushing to slide over part of the stud on the Z3/318ti subframe studs which allows them to mount flush to the subframe stud flange

In my brain this looks to me like a lot of ... I don't even know the proper term for this type of force, I keep thinking "cantilever" but I'm not sure? Anyways. I know they are supposed to be "solid" but I still don't like that big gap there. I am thinking what I may do is get a spacer machined to sit between the bushing top and the top plate


I also installed the DME lid and it cleaned the engine bay up nicely. The big question everyone seems to ask now is "when will the dual intake be reinstalled" and the answer is - once I get an electric fan installed that doesn't protrude above the top of the radiator. So, I don't know. It's not an urgent priority but is on the to-do list

Got the old subframe bushings out. I did end up using a different subframe that was rust-free

The bushings have been sitting in the freezer since I got them...

The aluminum subframe bushings ended up being a massive pain in the ass to install... but I got them in. I won't be doing these again unless I have an extra pair of hands to help hold the subframe in place and good access to my press. My press is in my storage unit right now and it was a huge hassle working around everything while still trying to hold it in the proper position...

Next was new trailing arm bushings - a lot easier than the subframe bushings! The trailing arms also got the rust spots sanded down and a lick of paint applied. Nothing crazy but I wanted to cover and protect the spots I sanded the rust away

I also got the old differential output flange seals replaced as well as new lock rings on the axles

Now it is time for final reassembly!


First was to clean the diff cover mating flanges to get a nice seal with the new gasket

Differential put together... I like the look, silver with black bolts. Matches the "silver and black" theme of the mechanical parts of the car

Then the subframe, differential, trailing arms installed. Little bit funny to think that the only parts that are original to the Dunklenator are the trailing arm assemblies. The subframe and differential are both from different Z3's

Later that night I pulled the diff bolts out one by one to add a little threadlocker and snug em down to the required torque spec of "gutentight" - I also marked the bolts, including trailing arm bolts/nuts with a paint pen to be able to check for anything coming loose (the camera flash did almost completely hide the paint pen though lol)

Last thing I wanted to do before installing it was paint spray some bedliner on the undercarriage back here, I didn't like the gray primer/light misting of green paint that was under there, plus I sprayed the front so I wanted to finish it out to the back


I did mask off the area by the differential mount hanger so I can monitor the area and especially the spotwelds. There were also a few areas I want to spray a bit more, but I ran out of the stuff. I focused on the areas that are hidden by the subframe, the "unfinished" areas can be accessed with everything in place

Installed!

I still need to finish a few things but the bulk of the work is done now... probably only an hour so of work before it can be test driven again! Also I am thinking I will remove the spare tire holder completely... it's pretty ugly and I have never installed a spare tire in any of my Z3's. I want to show off that diff cover!


First was to fill the differential... easy enough

Then out with the old e-brake cables

And in with the new...

One last shot of the rear stuff finished! Only task left is to bleed the brakes... I don't know where my pressure bleeder is (buried in storage somewhere) so I'm gonna go look for it for a few minutes but more likely than not I'll just do it the old fashioned way

Onto the next part!

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