JBR 2016+ MX-5 Rear Differential Mount

Took the car to Streets of Willow, and immediately felt a difference from the OEM set up. I have an OS Giken, supercharger and the AWR engine mounts on my ND1, there was quite a lot of wheel hop and odd behavior before, this dramatically reduced the wheel hops and the odd judder when exiting a tight corner (the bowl section in streets). My speculation is due to the stiffer AWR mounts, the PPF would twist more w/ the soft OEM diff mounts.

Installation was relatively easy! I know some people are having issues installing it, but I was able to get the old mount out and the new mount in w/o removing the subframe and even disconnecting the axles and drive shaft. I only removed the PPF and that was it.

I WOULD RECOMMEND this product for those that exclusively drive their cars on the track. My car is mostly 90% track time. Having said that NVH is pretty extreme, would suggest wearing some good ear protection when driving the car.

-- Joel C., Long Beach, CA ( 2016 Miata ) February 2024

I purchased this and installed it just before my trip to Miatas at the Gap in August. I also installed it with an OEM LSD swap I had planned. I noticed the performance improvement immediately. The wheel hop at launch is virtually gone. It is a month later and the NVH is very noticeable especially with the top up. So if you like a quiet car I would consider powerflex or energy suspension bushings instead. I made this upgrade primarily for performance improvements for autocross and TT. My next upgrade will be a full set of AWR Motor Mounts which compliment the JBR diff mount well. Overall I am very pleased with the JBR diff mount.

-- Robert L., Wilmington NC ( 2016 ND GT ) August 2023

Well made product, but NOT EASY TO INSTALL without dropping the subframe.

I didn't wanna mess up my alignment so I didn't touch my subframe, and this led to very tight space to:

1) reaching the 4 bolts on the top of the differential. Get an extra long arm flex head box wrench to make this much easier.

2) wiggling the stock brace out and putting the new brace in. Without lowering the subframe, you have to do both from the driver side. And I recommend removing the level sensor to create more space.

Overall, I like how the gear shift is noticeably more precise (no more guessing game on getting into gears). There's a bit of wining noise after 4-5k rpm, but it doesn't bother me at all.

If your stock diff mount is good, I wouldn't recommend doing this. If yours is bad like mine, then this is a cheap and nice upgrade for sure. My car is 50% track 50% street.

-- Curtis Z., Cupertino, CA ( 2017 Miata Club ) February 2023

A couple more notes on the installation for the 124 Spider. I dropped the subframe about an inch by partially unscrewing the 6 subframe nuts to give more room to the top nuts on the stock differential bracket. The top four nuts are extremely difficult to access on the differential bracket (particularly on the passenger side). These nuts on my car were so tight as to be nearly impossible to remove without a lot of patience and ingenuity (my solution:17mm wrench + carefully placed crowbar for leverage). As written above, moving the fuel vapor system integrity control module out of the way is necessary for massaging the stock unit out. Removing the stock bracket requires patience and can only be done towards the driver's side of the car. I did not move any fuel (or other) lines. The JBR unit is smaller and much easier to get in. Again, tightening the top four bolts is very challenging. It is impossible to get a torque wrench on the top four bolts without removing the subframe. I would guess the whole thing took me 3 hours with my car on jack stands. This is one of the few jobs I would outsource if I had to do it again.

-- Darren B. ( Fiat 124 Spider Classica ) January 2023

The mount made a noticeable impact to the rear end feel, giving more direct and planted on acceleration. Since I'm mostly driving mountain roads and canyons that are less than smooth, the feel translates into a lot more confidence and less bucking feeling/wind up when coming on and off throttle. I paired with with the front subframe bracing and strut tower bracing and this really helps the rear end achieve a similar feel and confidence on higher speed mountain roads from front to rear.

In terms of possible negatives, the initial noise from the drivetrain is pretty noticeable in terms of lower speed clunks such as when shifting and higher speed differential gear whine (over 80mph) but the sound doesn't bother me and it adds a bit of race feel.

-- Justin S., San Mateo, CA ( 2017 MX5 RF ) May 2022

Installed this brace a few weeks ago. There was initially a lot of driveline noise, but most of it has settled down. I can still hear clunking when shifting, but that is normal and not a big deal to me. The car definitely feels a bit more planted under acceleration, especially out of curves. Install wasn't bad at all. I recommend!

-- Nicholas W., Raleigh, NC ( 2017 Fiat 124 Abarth ) January 2022

This modification is a true game-changer. I can feel a little less drivetrain loss in both straight-line acceleration and corner exit. Much more consistent delivery of power to the rear wheels. A bit more gear whine and slight noise and vibration (but not harshness) coming from the diff. It increases the drama of revving out the motor above 5K rpm, but is not noticeable under 4,500 rpm. This noise and vibration may calm down after a couple hundred miles. Car feels a bit quicker in a straight line. The gearbox feels slightly more substantial and meaty with changeups, though this could be a placebo effect. Much more feedback from the rear axle under acceleration, compared to the mushy-feeling OEM differential brace. For the changes this brace has made to the performance and feel of the vehicle, this mod is a total bargain. Install is easy, although requires careful and patient hands and removal of the muffler. I cannot wait to try this mod out on track this Friday at Streets of Willow.

-- Chase E., Orange County, CA ( 2020 MX-5 RF GT ) April 2021