7 Tips and Tricks for E30 Rear Subframe Removal
It's finally come time to replace those 30+ year-old bushings barely keeping your e30's rear subframe and trailing arms in their place. For those of you who are reading this, this is likely your first time taking on this project and you're looking for any piece of information to make this intimidating job a little less so. I'm here to tell you this job isn't easy, but we can make it a little easier and the results are so rewarding.
Tip 1: Penetrating oil and lots of it
This step is the most crucial to ensuring everything goes smoothly. 24 hours before you begin this project, go ahead and take the time to get your E30 suspended safely on jack stands with the wheels removed and soak every nut and bolt associated with the rear suspension. Let it sit and reapply over a 24 hour period as often as necessary.
Take special care to hit these areas extra heavy
- rear subframe mount hardware (secures the subframe to the chassis)
- brake line connections
- sway bar end link hardware
- the hardware securing the rear muffler section of the exhaust (any exhaust hardware that needs removal)
- driveshaft to differential nuts
- hex head rear brake rotor retainer bolts
- diff mount
Tip 2: Drop the Diff
- 18mm nut/bolt securing the differential bushing to the chassis mount
- 4x 19mm bolts securing the differential to the subframe
- 4x 17mm nuts securing the driveshaft to the differential
- 12x E12 torx bolts securing the axles to the output shafts
- 2x 30mm axle nuts one on each hub (socket might need slight modification as pictured below to clear lock ring PN: )
If the subframe is coming out, the differential and axles are coming out too. Taking the extra time to remove the half shafts and diff will eliminate roughly 100 pounds from the subframe assembly making it much more manageable to maneuver when it drops. Use the e-brake to hold the axles while you remove the E12 torx hardware for the axles if you do not have a 3/8th inch impact. Soak the rear axle spline shafts in the hub with penetrating fluid and use a punch and hammer to tap them out if they have seized. The axle spline shaft ends should have a divot to act as a pilot for a punch and hammer or an air hammer attachment. Support the differential with a floor jack while you remove the hardware securing it to the subframe and rear diff mount. Once it is free, tilt the diff away from the driveshaft studs to clear the differential mounting tabs on the chassis and lower the floor jack to remove.
Tip 3: E-brake cables
If your emergency brake doesn't seem to work properly, or at all, then this is a good time to replace your cables and rebuild the rear drums while the subframe is out of the vehicle. Remove the emergency brake trim boot and you will see two 10mm nuts that secure the cables to the handle assembly. With the hardware removed in the cabin, the cables are free to slide out of their sleeves in the chassis. Be sure to check RealOEM with the last 7 of your VIN to make sure you get the correct e-brake parts for your E30 chassis.
Tip 4: Leave the rear shocks bolted in till the end
Like tip 2, this one is short and sweet. Leave the rear shock assembly bolted in at the chassis and the knuckles till the very end. As the rear subframe is hanging there by the last half inch of inner bushing race rusted in the chassis, the rear shocks will act as a support for the rear trailing arms and even out the load on those subframe bushings. Otherwise, the weight of trailing arms hanging down wedges the inner races of the subframe bushing recessed in the chassis making it near impossible to separate.
Tip 5: Hammer Time
Once you have everything unbolted it seems pretty straight forward, gravity should do its job and the subframe should just drop out, right? Wrong, more often than not the studs in the chassis for the subframe have seized to the inner race of the ancient OEM subframe bushings. We have a genius solution implemented by BMW as if they knew it was going to cause problems later. Remove the rear seat bottom and look in the corners of the exposed chassis for a couple of holes with a perfectly round bolt head inside as pictured below.
This is the top of the stud that is pressed into the chassis to secure the subframe. Return to the underside of the vehicle and be sure there is something in place to support the subframe when it comes loose. Thread the 22mm nuts on and give them a couple of good whacks up towards the chassis with a small sledgehammer.
The stud will recede up into the chassis breaking it free from the bushing's inner race. Use a magnet to lift the stud from the chassis after it is broken loose and set it aside.
More often than not, the inner races of the subframe bushings are rusted and seized in the chassis so you will need a 5/8x11 tap to thread the inner race of the bushing about 3 inches deep. Thread a matching 2.5 inch bolt into the bottom of the bushing race to effectively seal it. From the inside rear seating section, proceed to smash using a drift or punch and a sledgehammer to break the inner races free of their rusty perch by knocking the bushings down and out of the chassis.
Tip 6: Cardboard
This tip is more of a personal preference for the shadetree mechanics. Many of us don't have access to a commercial vehicle lift and the specialty tools you would find at a dealership. I've found having a large piece of cardboard to lower the subframe assembly and trailing arms down onto is the next best thing. It makes sliding it out from under the car much easier when those trailing arms want to drag along no matter what surface you're working on. This is especially helpful for you all who are flat-backing it in the gravel.
Safety Note: DONT FORGET TO HAVE A JACK OR JACK STANDS (PREFERABLY BOTH) IN PLACE TO SUPPORT THE SUBFRAME WHEN IT COMES FREE. IT IS VERY HEAVY AND AWKWARD.
At this point, you should have successfully separated the subframe from the chassis and have it supported on a jack. Remove the 19mm bolts that secure the rear shocks to the knuckle and carefully lower the subframe assembly.
Tip 7: Tap the Race
Still having trouble freeing the subframe bushing inner races from the chassis? Find yourself a slide hammer, a large tap to thread the inside of the rear subframe bushing race, and a matching bolt. Once you have tapped your races and attach your slide hammer to the bushing inner races with the bolt. Before you at it, be sure you have something to support the subframe when it drops. It won't take much from the slidehammer to free the subframe so make sure you're out of the way!