Below is my full review of Bruce aka ac427cobra's IRS Delrin/UHMW/Aluminum bushing package.
Initial Impressions:
As I opened the kit the first thing I noticed was that each set of bushings were packed separately with labels text side out in clear zip lock bags. The parts are top quality. In my opinion these bushings are of the same quality as Maximum Motorsports or Griggs Racing's parts. Everything is exactly as pictured in Bruce's pictures and no corners were cut.
Install:
Having done lots of automotive work including nearly every mod done to my cobra, these bushings are not easy to install but that isn't to say that is a negative on them, it just isn't an easy job. But if you compare how difficult these bushings are compared to some others I have encountered I would say they are as install friendly as you can get. Bruce has paid very close attention to detail once again and made many refinements to make things as easy as possible but don't attempt the install unless you have the proper tools, a lot of time, and a load of patients.
Driving Impressions:
The first thing you will notice is the planted dependable feeling the rear end gives you after install. The rear end is now planted and the first test is straight line acceleration.... YES no hop! The car either grips and goes or spins the rears depending on the available traction. I personally spun all the way through first gear and in to second with out a hint of hop. Turning under acceleration no longer feels uneasy. The car feels like you are driving on rails when on smooth roads. Bumps and road irregularities no longer agitate the car, the suspension now absorbs those without transmitting them to the car and the cars manners while on poor roads is that of a true modern sports car. While this may seem counterintuitive to what you would think with solid bushings installed but the bushings allow the suspension to do what it was originally designed to do before the NVH engineers lowered the bushing durometer to that of a marshmallow. While there is a small increase in road noise transmitted to the car, it is not even noticeable when a loud exhaust is present or the stereo is on. The largest increase in noise is from the differential because of the solid mounting but a little gear whine is tolerable. It is akin to the amount of noise increase going from the stock shifter to an aftermarket unit without the use of sound deadening materials. I have been flogging this suspension for weeks now and have yet to find a single flaw. In my opinion this is a must mod for any IRS equipped mustang owner who is serious about their vehicle's performance. If you are willing to put money in to the motor, or the appearance, put a little in to the handling of your vehicle you wont be disappointed.
IRS vs. Solid Axle:
For the last time I wish to say it, though I'm certain I will have to many more times. The ONLY time I believe anyone should swap their independent rear for a solid axle is if drag racing has become more important than any other use of the car and you are willing to make sacrifices in handling and road manners. In my opinion the IRS is the superior suspension system and Chuck Schwynoch, CEO of Maximum Motorsports agrees (link).
Final Thoughts:
I could not be more pleased with this kit. I have been advocating the system approach for years and it is nice to see someone address the bushings and differential bushings with such attention to detail while keeping costs to a minimum. I see absolutely no reason to purchase these parts from any other vendor. These are the best parts and the best deal. To top it off, Bruce is a great guy to deal with and stands behind his parts and is willing to answer any questions you may have, honestly I might add. Your mileage may very but I recommend these parts with no hesitation. I would be glad to answer anyone's questions with regards to my experience with these parts, other questions about the IRS, Mustang suspensions, or any other topic.
Additional Links:
My Technical Write-up on the 1999-2004 Mustang Cobra Independent Rear Suspension
The IRS Tech Article
Full Details on my Car
My Cobra
The Bushing Kit Reviewed Above
The complete IRS Delrin/UHMW/Aluminum bushing package
Initial Impressions:
As I opened the kit the first thing I noticed was that each set of bushings were packed separately with labels text side out in clear zip lock bags. The parts are top quality. In my opinion these bushings are of the same quality as Maximum Motorsports or Griggs Racing's parts. Everything is exactly as pictured in Bruce's pictures and no corners were cut.
Install:
Having done lots of automotive work including nearly every mod done to my cobra, these bushings are not easy to install but that isn't to say that is a negative on them, it just isn't an easy job. But if you compare how difficult these bushings are compared to some others I have encountered I would say they are as install friendly as you can get. Bruce has paid very close attention to detail once again and made many refinements to make things as easy as possible but don't attempt the install unless you have the proper tools, a lot of time, and a load of patients.
Driving Impressions:
The first thing you will notice is the planted dependable feeling the rear end gives you after install. The rear end is now planted and the first test is straight line acceleration.... YES no hop! The car either grips and goes or spins the rears depending on the available traction. I personally spun all the way through first gear and in to second with out a hint of hop. Turning under acceleration no longer feels uneasy. The car feels like you are driving on rails when on smooth roads. Bumps and road irregularities no longer agitate the car, the suspension now absorbs those without transmitting them to the car and the cars manners while on poor roads is that of a true modern sports car. While this may seem counterintuitive to what you would think with solid bushings installed but the bushings allow the suspension to do what it was originally designed to do before the NVH engineers lowered the bushing durometer to that of a marshmallow. While there is a small increase in road noise transmitted to the car, it is not even noticeable when a loud exhaust is present or the stereo is on. The largest increase in noise is from the differential because of the solid mounting but a little gear whine is tolerable. It is akin to the amount of noise increase going from the stock shifter to an aftermarket unit without the use of sound deadening materials. I have been flogging this suspension for weeks now and have yet to find a single flaw. In my opinion this is a must mod for any IRS equipped mustang owner who is serious about their vehicle's performance. If you are willing to put money in to the motor, or the appearance, put a little in to the handling of your vehicle you wont be disappointed.
IRS vs. Solid Axle:
For the last time I wish to say it, though I'm certain I will have to many more times. The ONLY time I believe anyone should swap their independent rear for a solid axle is if drag racing has become more important than any other use of the car and you are willing to make sacrifices in handling and road manners. In my opinion the IRS is the superior suspension system and Chuck Schwynoch, CEO of Maximum Motorsports agrees (link).
Final Thoughts:
I could not be more pleased with this kit. I have been advocating the system approach for years and it is nice to see someone address the bushings and differential bushings with such attention to detail while keeping costs to a minimum. I see absolutely no reason to purchase these parts from any other vendor. These are the best parts and the best deal. To top it off, Bruce is a great guy to deal with and stands behind his parts and is willing to answer any questions you may have, honestly I might add. Your mileage may very but I recommend these parts with no hesitation. I would be glad to answer anyone's questions with regards to my experience with these parts, other questions about the IRS, Mustang suspensions, or any other topic.
Additional Links:
My Technical Write-up on the 1999-2004 Mustang Cobra Independent Rear Suspension
The IRS Tech Article
Full Details on my Car
My Cobra
The Bushing Kit Reviewed Above
The complete IRS Delrin/UHMW/Aluminum bushing package
But the '01-'04 31 spline halfshafts should be sufficient for 90-95% of the people's needs. It's only the guys putting down more than 500 hp and pounding out holeshot after holeshot at the drag strip on slicks or DR's that need them. It is also my opinion that 90% of the broken halfshafts are NOT broken from sheer power. They are broken due to IRS assemblies and differentials gyrating and wheel hopping out of control because of all of the rubber mounts. Plain and simple. 
