Steeda S550 Mustang Differential Bushing Insert System - Street to Full Race Combo Kit EcoBoost, V6 (2015-2021)

8 Review(s)
$10.00 (4%)
Steeda Autosports has once again taken the S550 Mustang to the next level of performance and comfort with our exclusive S550 Mustang Differential Bushing Insert System - Street to Full Race Combo Kit EcoBoost!

Part Number: 555 4444
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Steeda Autosports has once again taken the S550 Mustang to the next level of performance and comfort with our exclusive S550 Mustang Differential Bushing Insert System - Street to Full Race Combo Kit EcoBoost! This combo kit comes complete with our Urethane and Aluminum Differential Bushing Insert Systems. When our engineers sat down to design these kits, we had to come up with a way to increase performance without sacrificing an ounce of drivability using urethane bushings. Our engineers then also took our hardcore racers into mind when designing our kit which utilizes aluminum bushings.

Unlike our competitors' kits that will absolutely increase NVH (noise, vibration, harshness), take 3-4 hours to install and force you to permanently modify the rear IRS suspension with a Sawzall, Steeda's does not! Our kit installs in under 1 hour, adds little to no increase in NVH , is adjustable and can be easily removed - it simply doesn't get any better than this!

Both our urethane and aluminum bushing inserts aim to minimize pinion angle changes, increase traction, eliminate wheel hop and differential deflection.

Our urethane bushing inserts are made to Steeda's exact specifications and durometers, our kit comes with 3 different bushing options - our red 'street' 80 durometer bushings, our black 'performance' 90 durometer bushings, and our in-house billet 6061 aluminum bushings 'race'. Both urethane bushing options will increase performance with no increase in NVH, a Steeda-exclusive. Steeda's race kit installs in under 1 hour, is adjustable and can be easily removed. Since NVH was not an issue when designing the aluminum inserts, our engineers aimed to maximize reduction in wheel hop and differential deflection.

Steeda's kit adds the strength and support the OEM bushings need to perform the way our customers intended. Once again, this is not a permanent modification - there is no drilling, cutting or pressing required. Simply loosen and remove a couple bolts and this kit installs in less than 1 hour. Bushings are included for both the front and rear differential mounting locations. Grade 10.9 hardware is included with zinc-plated washers.

Note: Does not fit GT350 or Mach 1. Due to changes in the OE subframe bushings, the bushing inserts will not fit 2021 GT500's or 2022 Mustang's.

Product Benefits
  • Limits IRS differential movement while increasing traction and eliminating wheel hop
  • Urethane bushing inserts - little to no increase in NVH unlike the competition
  • Aluminum bushing inserts - designed for the abuse seen racing down the 1/4 mile
  • Easily removable, not a permanent modification
  • 100% designed, manufactured and made in the USA
  • Installs in 1 hour or less

CA Residents: Cancer and Reproductive Harm WARNING

Fitment & Features


Manufacturer: Steeda Autosports
Made in USA: Yes

Installation Information:

Level of Difficulty: Easy
Install Time: About 2 Hours
Tools Required: Basic Shop Tools

Vehicle Fitment:

Fits Model Year: 2015, 2016, 2017, 2018, 2019, 2020, 2021

Customer Reviews

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Average Customer Ratings


The difference is night and day
Hey guys I just recently installed the the Steeda IRS & Differential bushings (red bushings) along with the IRS alignment kit. All I have to say is WOW! I installed it myself in the garage. It was very straightforward and easy. The difference is night and day. The car would have some really bad exaggerated wheel hop. I didn't feel much confidence with the car on launch and handling. I almost started to question my driving skills. On handling you get a lot of the control back. The car becomes more predictable when the rear breaks loose. When launching, it dips and rips off the line with very minimal wheel hop to where the car can grip. It's a very very good confident feeling you get. The wheel hop I would say is about 95% gone. The 5% wheel hop that you do feel is very light and almost unnoticeable. Anyone who is in doubt or questioning on getting the kit, I highly recommend it and it's worth every single penny. You won't regret it!
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I am pleased to say the thud is gone
So I was unaware that people had seen an improvement in the thud after installing the diff bushing so I hadn't really paid attention to it at all. My car is a GT PP with a ver obvious and annoying thud. Well, after paying more attention to it today I am pleased to say the thud is gone. That being said, I did notice a more pronounced shift if that is possible. Maybe a little more notchy, but I like it. Feels like the shifter drops into place easier. Bushings look to be a great investment and mod!
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First time the car hooked up for me without bouncing everywhere
Steeda diff bushings were the biggest surprise. I have the subframe mounts on back order, so I will get them in next week. But I was amazed at the difference the bushings made. Only a slight wheel hop on wet roads. First time the car hooked up for me without bouncing everywhere. Used the red bushings, no noticeable NVH especially with the new exhaust. Can't wait to see how it does with the subframe mounts.
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I am beyond happy!
Got my Steeda differential bushing kit installed today...and I am beyond happy! I decided to go with the red Street bushings because I was afraid of NVH and I'd say the thud is 95% gone. It is at a point that I feel like if the car had come this way from the factory, I'd have never even noticed it. Such a joy to drive now and not hear that damn noise! I really think each car must do it to a different degree and mine was particularly bad because I just can't imagine anyone accepting that sound in a car otherwise so nice. I'm sure that with that kit or the Steeda aluminum bushings the sound would be 100% eliminated but I'm completely happy with it now and with the red Steeda's there is ZERO added NVH. Don't believe those that say you'll have to live with that awful sound. You don't. Haven't tested out the wheel hop but if that's better then that's just icing on the cake!
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Most noticeable improvement in the car
IRS differential bushings, aluminum: Most noticeable improvement in the car. Probably the best suspension mod I have made. Yes, you shift hard you'll feel a slight clunk as power hits to the rear end and has nowhere to go but to the tires, but that's exactly what I want. Car barely squats at this point and yet is still very comfortable for easy cruising. I have noticed a bit of driveline whine since installing them, but it's so light I don't even notice. Besides, I have a Corsa to listen to and that definitely drowns it out.
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I am a Steeda believer
The car is a totally different handling car. Took the wife for a ride today and she said it is smoother than before. Much less bouncy. That is good news to me. Cause if the wife is happy I am happy. But I will say that these mods have really changed my confidence in the car. I had one little 30mile spirited section with S curves on my way home that normally when they say 45mph.. you can take them at 55mph... I took them at 70mph and the car was just planted solid. No roll, no rebound and no breaking loose on the rear when I accelerated from the apex. It just transitioned smoothly and predictably. Now the only thing the wife did notice was the gear whine. Yes the Red differential bushing will cause some gear whine, but I have been told that replacing the stock gear oil in the rear end will help quiet that noise down. We will see as I will most likely change mine out here in the next week. Amsoil or Royal Purple is what a lot of people recommended. So, all in all, if someone is on the fence about these suspension upgrades, just do it. The guys at Steeda are top notch and know their stuff. Almost all of them have Mustangs and the owner even races them. A final shout out to [email protected] What a great help he was. He made sure everything was ready and there, his recommendations were spot on. David, again, Thank you man. I can hardly wait for the next batch of Steeda goodies come out.. Count me in already. I am a Steeda believer.
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Definitely worth purchasing
I installed the red bushings Friday night while installing my Borla S Type cat back. The red have no added HVH. Great street setup. Immediately on first take off noticed the rear axle was more solid. Definitely worth purchasing.
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Solid Mod
Give yourself 3 hours to do this mod. No real increase in NVH Manual drive line slop is reduced further with these. SOLID MOD buy these. Not sure I would ever need the Aluminum ones but I bet I could swap them in an hour now that I'm familiar.
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