What's different about this Cosworth diff mount?

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cosworth unit


stock one here

[anglin]

The "Cosworth" unit is probably referring to the Grp-N differential mount. The Grp-N mount uses a harder rubber to suspend the metal parts in the assembly. This allows for a notably more responsive rear suspension, since there is less deflection in the bushing. And yes, you will notice an improvement in rear suspension response and control if you install the differential mount only. It is quite amazing.

The differential mount in the bottom picture is an EARLY XR4Ti (and probably XR4i) differential mount. You can tell this because the area around the steel portion in the center is filled almost completely with rubber. This mount differs from the late mount in this regard (and the bolt slots for the mount-to-chassis connection are smaller, too).

The early diff mount wasn't around long. Brad is much more capable of putting dates to the "early" than I am.

The Grp-N mount has the same rubber to metal ratio as the late XR4Ti mount. The early diff mount has a different rubber to metal ratio. You can see the difference in the pictures. The early mount is substantially stiffer than the late mount (not Grp-N) due to the increased volume of rubber filling the space. It may be a poor man's Grp-N mount, assuming you use the correct bolts for the application. However, I'm sure they changed designs for a reason.

The Grp-N mount will look (edit: almost) exactly like a late XR4Ti diff mount.

The problem with the pictures is that they are hosted by ebay. This means when the item gets flushed from the ebay database, we'll lose the pictures. I've taken the liberty to yoink those pictures and post them on my server. Now ebay can't pull them down (without a court injunction). In addition, I've added a picture of the stock mount to compare to the Grp-N.

Early mount:

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Grp-N mount (edit: this is not a Grp-N mount, see later posts):

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Late mount:

[Grayson]

I suspect that "Cosworth" one in the picture is NOT a Group N differential mount, but is merely a stock "late" differential mount. There is certainly no reason whatsoever to associate the word "Cosworth" with "Group N".

[85merwhat?]

Does the flat top on the grp-n make a difference compared to the tapered top on the other mounts?

[anglin]

I suspect that "Cosworth" one in the picture is NOT a Group N differential mount, but is merely a stock "late" differential mount. There is certainly no reason whatsoever to associate the word "Cosworth" with "Group N".

True, Cosworth does not equal Grp-N. However, some folks may associate the two and call it by some inaccurate name. I've never heard mention that a differential mount that came on a Cosworth originally was of harder rubber, like the Grp-N mount. So, if you are interested in purchasing the part as a Grp-N part, you'll need to get confirmation that the mount has the harder rubber.

To make things worse for my original case, here's a link to the auction:

http://cgi.ebay.com/cosworth-rear-diff- ... dZViewItem

I suppose he would have mentioned something about it being a performance part if it had the harder rubber.

Does the flat top on the grp-n make a difference compared to the tapered top on the other mounts?

The top is the same on the Grp-N mount as the others. The angle that the picture was taken at just makes it look different.

If I could get my hijack on for just a second... the seller of that diff mount has some interesting stuff; including this Grp-A 9" diff ring gear set.

http://cgi.ebay.com/cosworth-group-A-ra ... dZViewItem

[XR4Timan]

Guys, sorry to burst your bubble but that diff mount off Ebay above is the IDENTICAL one off your Merkur Having sold over two dozen diffs, I know.

You would have paid a crazy exchange rate and expensive shipping for the same thing that you can get from any Merkur

[anglin]

Guys, sorry to burst your bubble but...

There was a bubble that was going to get burst? Nah. Pretty sure we have this one figured out.

[anglin]

I went back and checked my pictures of the real Grp-N mount that I have, just for the sake of comparison. Wow, I apparently wasn't paying attention to it at all. There are several details of it that are different. Assuming all Grp-N mounts were built in an fashion identical to this one, they should be reasonably easy to identify in a picture.

Here's the actual Grp-N mount. It's clearly patterned after the stock late mount, but not identical.



I have all these pictures for reference. Maybe I should refer to them, huh. Oh well.

[Ray]

With the pricing and quality of your aluminum / polyurethane rear diff mount, why even bother looking further?

[xrian]

Ditto that thought!!

With the pricing and quality of your aluminum / polyurethane rear diff mount, why even bother looking further?

[anglin]

With the pricing and quality of your aluminum / polyurethane rear diff mount, why even bother looking further?

Word.

BTW, tomorrow I'll finally be picking up the solid aluminum differential mounts from the anodizer. That's the very last step in the process before they are available for purchase. It's about time. I finalized the design 10 months ago then did the prototype testing. They are finally ready. Phew. The rear end in my racer is reasonably well controlled. This year it is going to get crazy. I can't fleepin' wait.

[Ray]

just to bump this back up --

i just finally installed the rear diff mount from MC2Racing since i put my merkur back on the road yesterday.

it was quite possibly the easiest mod i've done to my car. i've never done one, and it took me less than 45 minutes total. the fitment is perfect, the quality is amazing. anyone considering this piece -- you wont be disappointed. my car is awaiting a full suspension transplant soon, and even with the OEM completely worn bushings, soft springs, and dampers that are cushy, it feels better.

[thesameguy]

Is there any downside to the solid mount? I'm interested in replaceing mine if it does indeed improve rear-end response, but as always curious why one part is better than the other, and why Ford did it one way...

[vcallaway]

Think of it as a vibration damper.

replacing the diff mount with a solid one and not doing the other bushings is asking for trouble. The beam bushings and trailing arm bushings all have give in them. If they are old and the diff mount is solid you have placed a tremendous amount of stress on those mount points. Busting a diff case is not high on my things I want to do list.

Personally, I would only use a solid diff mount combined with a solid beam bushing. And only for racing.

[Ray]

I have the polyurethane (not solid) rear diff mount, and i'm going to be replacing all the bushings in the car in the coming weeks with polyurethane and nylon. (i dont drive my merkur often).