Diff. Bushings

About a month ago I pulled the plug on the Z1 urethane differential bushings for my bone stock sport sedan. My stock bushing had not blown yet (which I only found out after I drilled into the rubber and was blasted with oil) but it had deep cracks forming in the rubber. I just put the subframe collars in yesterday.

Installation was grueling to say the least. I am not experienced when it comes to jobs like this but I was not expecting it to take me 10+ hours in total without using Z1’s removal tool. Because of this, I would not recommend getting these unless you absolutely need new bushings, are already doing work on your differential, or are planning to have a shop install them

I ended up using an air chisel to roll up the metal outer sleeve of the rear bushing, and pry the front bushings out. A 10 inch hex bolt, some nuts, and the old bottom washers from the front bushings were used to make a tool similar (and much cheaper) to the one Z1 sells. Even with this tool the rear bushing was still a pain to finally get in however, the front bushing went in easily by hammering them in.

Driving with only the differential bushings installed, I did not notice any increase in NVH. The rear did feel tighter and the torque came on harsher, but it was not a grand difference. Body roll was seemingly increased substantially.

Subframe collars

Installing these was a breeze compared to the differential bushings, and took me a little over an hour. Even though they do require quite a bit of force to insert, this was probably the easiest install I have done yet.

After driving about 15 miles city and 15 miles highway with both the collars and bushings installed, the rear end has become noticeably tighter. I was pleasantly surprised by how much body roll was eliminated, and how instant the torque was felt. The increase in NVH was not as pleasing though. I expected there to be some increase, and hopefully this is due to an easily fixable error I made while installing, but at low speeds and accelerating from a stop metal rubbing against metal makes it sound like I’m driving the most neglected beater imaginable. It is not noticeable outside the cabin, but inside it is quite loud.

Overall I recommend both of these as a combo. In my opinion, unless you need to replace your differential bushings replacing them with these is not worth it on their own. The subframe collars however, I feel made a great difference in handling, and are easy to install.

 

Good review.

Right or wrong, I've always had the opinion that Z1's subframe collars are more effective for a car that's somewhat tired. That said, how many miles on your old sedan? Shame about the NVH from the collars, this is the first time I've heard about that (no pun). Don't beat yourself up too much about how long it took to get the diff bushing installed. Even an experienced mechanic could spend half a day on that stuff, really inflating labor costs.

If you're good with where you are on these mods, I'd recommend poly motor mounts in your future. All these little incremental suspension mods add up, and eventually transform an otherwise comfortable sport sedan into a fairly aggressive driving experience. That's the compromise... once you go stiff, you can't just turn it off.

 

It is a 2013 with 76k miles on it. I have seen a few other reviews that stated there being squeaks and increased tire noise after adding the collars. Both have been true so far, but the squeaks have subsided some after about 120 miles. Long term, I do plan to make the car fairly stiff. But next, I’ll be adding an oil cooler and a better radiator to help ward off this Texas heat.

 

I was told to stick with rubber bushings because polyurethane stiffens the ride considerably and are noisy; they can squeak.