Upgraded Axles for a Track Car?

[rhk118]

Hi All, just what the title says...If building a track car, is it a good idea to upgrade the rear axles (IRS) or are the stock FFR ones good enough? In the process of building my car and wondering if worthwhile to just upgrade them now rather than potentially having to replace one later, also a part I have been waiting for from FFR...3.55 rear, close ratio T-56, will likely be in the 450-500 HP range.

[Jim1855]

I have the 2015 Mustang IRS, the new style, and building (slowly) a track/street car. HP in the mid-500 range, same motor from my previous Superformance cars with the older IRS systems. Didn't break anything with the T-Bird IRS except CV boots. The new IRS is supposed to be much stronger. I'm not concerned and even choose the aluminum diff case to save weight, about 25#. But I have no time in operation, so my selection isn't tested.

Tires are usually the weak link in the driveline, drag radials change things and are kinda tough on the system, dumping the clutch starts the process. This isn't the normal for track cars.

Check the Mustang forums, not sure what you'll find but if axles and parts are breaking these are the guys that will know. Downside, they run different axles, ours are shorter so we don't have the same options.

Jim

[Gordon Levy]

I don't see that being an issue.

[edwardb]

This question is asked frequently. Usually the same answer. The ones from FF are fine. They are using the stock CV joints on a shortened axle. Haven't heard of any failures. Keep in mind are designed for a much heavier car. Only issue I've heard about on track cars is boots. Some are tying them up somehow as apparently they can expand and fail. Know nothing about it (and my explanation might be suspect) but I have heard of this from a few builders. So something to check.

[rhk118]

Perfect, thanks guys. Will stick with the stockers. I’m not drag racing and not going to be doing intentional clutch drops, road racing only. Had seen something about putting narrow boots on them Paul.

[Jim1855]

In the past plastic wire ties were used in the inside "v" (small diameter) of the CV boot pleats to minimize expansion w/o or at least minimal restriction of the angular movement. The grease inside the boots acts as a weight, think a bunch of clothes in the washer, and throws things out of balance. Too much grease weight is often the problem and the expanded boot contacts something and wears through during the suspension travel.

Holes in CV boots are a messy problem and a PITA to fix, well at least for the first few times until you get a good system worked out.

Jim