Polyurethane Differential Bushing Insert Kit for NA and NB

I am very happy with the results of installing this easy to install bushing insert kit. The car just feels more settled to me. Great value for little money.

I installed these over the weekend. Installation was 3/10. Had to drop rear tie and FM butterfly bracing and undo the muffler from the midpipe (I have the FM Catback) to give enough flex to the unbolted differential housing to be able to slip the poly doughnut rings (top part of the insert) into their intended locations. Of course, unbolting everything took longer than installing the parts.

Driving impressions are positive. No detectable NVH and more precise shifting. 1-2 and 2-3 are the most noticeable. Downshifting through all the gears feels tighter with much less bounce (when not done perfectly).

I'm a very satisfied customer.

Installed these last November when I installed a rebuilt diff. Drove it for the first time last week.

My car has 50k on it and the original bushings are in pretty good shape. These still made a good impression during shifting. I am very satisfied with the performance.

These were inserted in a 1999 10AE that is naturally aspirated and is never tracked but instead is driven at 7 to 8ths on the road when appropriate. My Rear Differential Bushings are OE, in good condition and I've never tried anything else but OE rubber RD bushings. All that said, these inserts changed the entire nature of the car with regards to the way it handles, how tight the overall feel of the car is and how it shifts. I've replaced the motor mounts, installed Paco Strong Arms and am running a FM level 2 suspension along with a short throw shift kit, along with the FM Happy Meal. All this is to say that this is a very worthwhile installation and I'd recommend it for three simple reasons: 1) the price point; 2) the results mentioned previously; 3) not needing an open flame during installation. As for the installation it took about an hour at my ASE shop of choice on a hoist, so it wasn't impossible but I wouldn't have wanted to do this in my driveway. In closing, the greatest trouble I've had with these part were finding them on the FM website; have to do a "bushing insert" search to find them; doing so through the drop-down menus would have been too challenging and taken too long. In short, buy these parts, do it now and reap the rewards of a better Miata (NA or NB).

tl;dr: Get them! Easy to install with a noticeable impact. (If you need new bushings all together however, these are more of a band-aid fix.)

96' NA, 118k miles. Before the fillers, the powertrain always felt a little "dampened", with them in, there's definitely an improvement! (I think I just need new bushings though). The power feels more "direct", and starting from a stop has been much easier. No noticeable NVH increase, however my car is pretty rattly as is, so hard to tell. If yours is a DD, I doubt it would be noticeable.

Install took about an hour total (plus an hour for the penetrating oil, 30 mins rummaging through tools, etc). Very easy to install, I opted to support the diff with a jack, remove the two brackets, and install the part that way, no removal required! I did end up cutting the top pieces in order to get them around the bolt, as I doubt this would impact performance too much, and I wasn't in the mood to remove the exhaust and/or PPF.

If I were to go back to before I bough them, would I buy them again? Defiantly! Cheap parts with a noticeable impact and easy install are the best parts.

Useful notes: The flat side of the top piece faces up. On the bracket, the middle nut is a 17mm, torqued to 69-75 FT/LB, the two 12mm nuts are torqued to 18-22 FT/LB. Use some penetrating oil and wait at least an hour before install (a broken bolt/stripped nut turns a 1 hour job into a 2 day ordeal).