I am the one that engineered the mc²racing aluminum & polyurethane diff mount.

The diff mount is a tremendously important mount to upgrade, and it is often overlooked. On our autocross Merkur XR4Ti, we were having a lot of trouble with rear suspension deflections - which in our case was on the order of inches. We minimized this problem by installing a Group N (909) diff mount, and I have been a HUGE fan of the Group N diff mount ever since. Last year I wanted to pickup a second Group N diff mount, but when I went to order one from GGR I discovered that Ford had discontinued them! To the drawing board I went.

Now, I modeled the aluminum & polyurethane diff mount after the Group N diff mount. The critical dimensions are 100% identical, and the effective stiffness and NVH are identical. I went through several test bushings with a variety of different durometers and tolerances before selecting the one that is currently in production. I can say based on first-hand experience that you can not tell the difference between a vehicle equipped with a Group N diff mount and one of our diff mounts, which means that I accomplished my goal.

Of course, our diff mount has many advantages over the Group N diff mount since I don't have any bean counters watching over my shoulders like the Ford engineers do. Our mount is about half the weight, yet is quite beefy. Our mount is also cheaper. I paid $180 (£97.3 today) for my Group N diff mount 5 years ago, yet I sell our diff mount for $160 (£86.5 today). Finally, you can replace the bushings. When the Group N diff mount goes bad, it's bad forever. When our mount goes bad, you just stick in two fresh bushing "halves", which cost about $25 (£13.5 today) total.

We do have the solid diff mounts available also, but those are for cars that do not see street duty at all. If you ever drive your car on the street, use a polyurethane diff mount. If you never drive your car on the street, use a solid diff mount. It's that simple, and there are no exceptions.

I just finished up a design last week for a weld-in plate and sleeve kit to allow the rear beam to be solid-mounted for a much lower cost than using alloy beam mount bushings. The kit includes two upper circular weld plates, two lower circular weld plates, and two stepped center sleeves. The material is 4130, which is very strong and easy to weld. This is a better solution than alloy beam mounts, as it is cheaper and stronger. Alas, it is not a reversible modification.

We do manufacture alloy beam mount bushings upon request - I keep material on hand at all times so that I can make them in a hurry - but they are not cheap. We use a billet design that does not use any of those retarded spacer rings, so there is gobs of machine work involved. They do go in nice though, and of course this modification is reversible.

Pretty much everything people have said in this thread has been sensible. Good job guys!


Grayson
www.mc2racing.com