The 300ZX frame bushing repair was surprisingly the hardest repair I ever performed on my two-door Nissan sports car. The rear suspension on the 300ZX Z31 model is quite complicated and very different than your average American car. At the very bottom is an exploded view picture from the service manual so you can see this for yourself.
The rear suspension is completely independent and drive shafts coming out from the differential are actually rear CV axles. The back suspension is completely adjustable including rear castor, camber and toe as well. In fact negative camber is often seen on the older models due to coil spring sag. This can cause tire wear as well as poor handling.
My problem with the rear suspension was the right rear frame bushing deteriorated from dry rot and completely let loose. This is a major supporting point for the rear suspension and is largely responsible for holding everything together back there. Note that in the Nissan service manual they called this item a sub frame member insulator.
Repairing the 300ZX Frame Bushing
I will include some pictures of what the z31 rear suspension looks like (below) on this type of car. But take my word for it this repair was completely necessary. The rear frame bushing looks very much like an engine mount with a steel retainer bonded to a large rubber bushing.
This allows the rear frame member to be connected to the uni-body structure and the rubber provides some insulation between the two hard metal points.
Unfortunately on the Z cars the frame bushing is pressed into the frame member from the factory. Nevertheless, the replacement bushing also needs to be pressed in.
What this means is the sub-frame has to be completely removed from the vehicle. At first glance it doesn’t seem like it would be that hard of a job as in that there are not too many bolts attaching the frame to the uni-body structure.
However, the real problem is that several other items attach to the frame and these need to be removed. For example, the rear control arms and the rear sway bar.
The Hard Part about Replacing the 300ZX Frame Bushings
To make a long story short, the problem with the repair was that nothing wanted to come loose. The vehicle at the time of the repair was about 12 years old. There was well over 150,000 miles on the car. These rear suspension bolts were never disturbed during this vehicles entire life and they didn’t want to be disturbed now.
I soaked everything in liquid wrench for several hours. Finally I had to break out the torch and basically cut all of the bolts off. This is where the problems became serious. Some of these bolts that I had to destroy are extremely specialized cam bolts. Also taking the torch to the rear control arms destroyed the rear control arm bushings.
This meant ordering some very hard-to-find parts from the Nissan dealer. This also puts the car out of commission for a couple of weeks. And this was my daily driver. Also note that when I went to press out the old frame bushings from the sub-frame they also did not want to budge. Again it was necessary to use the torch.
I’m not a big fan of using the torch and I only use it when there is no other choice. Replacing the 300ZX frame bushings left me no choice and also left me without a car to drive for a couple of weeks. If you’re frame bushing separates, deteriorates or plain lets loose like-mine did you’re going to have to replace it. Just make sure that you plan for the worst-case scenario and order all the parts you may need well in advance.
More information and pictures of the this common z31 problem can be seen on this next page about 300zx frame bushing repair (not my website). For more of my recent posts visit this blogs homepage and get some auto repair information.