I finally saw a Jag IRS setup

[Yetiman]

Well, breaking the axles can be done.


Happened during an autocross speed shifting very hard from first to second. The car simply rolled to a stop and would not move on it's own power (which kind of surprised me with the limited slip).
This is a 1962 XKE rear, which has weaker axles than the later ones. They were replaced with chromoly axles and no problems since with the same kind of treatment and worse.

[G.R.]

There have to be hundreds, if not thousands, of street rods/hot rods and Cobra replicas running the Jag rearend.... let alone in original Jags since "62 or so.
Sure some have failed...due to maintence, negligence or fatigue .... or ignorance/stupidity on the owners part.

It must be he!! to be an engineer (no offense meant if you are one)
If I worried about every little niggly thing about any car I drive I would never drive it, be it the replica or the daily driver.

[double ugly]

I don't think I would have ever crawled into a fighter if breakage was on my mind. Paranoia sets in much later in life.
John

[Tom Wells]

Yetiman,

The car simply rolled to a stop and would not move on it's own power (which kind of surprised me with the limited slip).

Actually this wouldn't surprise me.

When the axle lets go, my bet would be that the top of the tire gets up against the body.

In my car if the tire leans in toward the center, the top of the tire would quickly come into contact with the seat bucket. This would most likely have two effects: The tire would act as though its brake was applied, and second, it would not lean any further. In my car the angle of lean would be very slight since the tire occasionally contacts the body at that point under full deflection... Other car bodies may be different.

That axle failure is not unusual on Jags - probably more common than the u-joint failure. Glad you only had a "Maalox moment" and did not accrue any personal damage CWI http://www.cwiinc.com/index.html sells HD parts for those axles that help a lot.

BTW, Mustang-type IRSs suffer from similar weaknesses, so drag racers tend to go for the live axles instead, and even those occasionally break. A stick shift with repetitive very hard launches at a drag strip using slicks is not a good application for an IRS.

Regards,

Tom

[rdorman]

If they break, what you say is true. Every one knows what you have pointed out, not an 'ideal' design. Any component, no matter how well designed, can fail. If you are that uncomfortable with Jag rear ends, simply don't get a car with one. To answer your orignal question, "Yes, it is common knowledge that it is not an ideal design" However, it is well executed. Kind of reminds me of the Porsche 911. One of the more interesting ways to describe the basic layout of the 911 I have heard is "A bad idea carried out to perfection" Who ever thought that hanging the motor out behind the rear wheels on a sports car must of been on crack But damn do I love them

[Lowell W]

Old Dog,

I raised the same issue last year sometime and got pretty much the same response: "Well, yeah, it probably could, but I don't worry much about it...".

Some of the Jag-based IRS setups do have an upper link, which seems to me to be a good idea.

Lowell

[badrich]

Yetiman: I used to speed shift regularly back in the day, but the first time I did that autocrossing in my 365 HP Stingray with some brand new 11" slicks, I stripped my spider gears and had to limp home, clunkedy, clunkedy, clunk. I may shift my Cobra quickly when necessary, but now the right foot comes off the gas, ever so briefly. I have beefed up my Jag rear end considerably and so far it hasn't given me any grief. Rich

[olddog]

Well thanks to all who responded. It did help me get some things straight in my head. More comments welcome.

29 years of working under safety taken to ridiculous levels has had its impact. To give you a hint, I can be fired for not holding onto the hand rails, when walking up or down steps. Ladders require three points of contact at all times, both feet and one hand or both hands and one foot.

So the Jag IRS is out for me, and a scatter shield around the clutch. Drive shaft enclosed. Rev limiter about 6500 RPM. What will Ernie think of me now? I must be a whimp.

[rdorman]

One thing is for sure... when you are done with your car, it should be sturdy! Sounds like a street driven spec racer with a solid rear is the way to go for you. Don't forget 'real' seats, the six points and arm restraints Not a darn thing wrong with being safe (of course, consider the source, a guy with no roll bar and a jag IRS).

[427 S/O]

767Jockey, they were purchased and came with brackets for the emergency brakes, I don't recall the manufacture. I'll contact you if I can find my receipt.

[427 S/O]

767jockey, the calipers are wilwood forged dynalite.

[avanti-176]

427 S/O-767jockey,
I think these are what you are looking for.....

http://www.cwiinc.com/brakes.htm bottom of page.

I just talked to them the other day and the setup is about $700. I will probably get it within the next month or so.

Dan

[427 S/O]

Mine are a little different and cost much less.........

[avanti-176]

Originally Posted by 427 S/O

Mine are a little different and cost much less.........

really?? Boy,if you could dig up the info I would really appreciate it. This is the only kit I have been able to find.

Thanks,
Dan

[427 S/O]

If I can find the receipt I'll pass it on...

[Tony Ripepi]

Hi Guys,

I had a Jag rear end in my Unique with a 427/Tremec combo, upgraded axels, rear link and beefed up the mounting and it worked great. George Petrus in SoCal company name Accurate Machine makes a version on the JAG rear that takes it a major leap forward from there.

Take a look at these.

http://www.cobraracing.com/ProductsAMP.html

TR

[427 S/O]

Nice stuff TR, IMHO it's more for a show car than a driver. I purchased some high end center section bolts from CWI a couple of years back, during the phone order I ask which rear end was best, they said the 89-95 HE was much stronger. I picked up one at a local salvage yard for $500, it has the aluminum cover.

[Anthony]

Originally Posted by olddog

Are there any modern cars being produced today with this type of design?.

Corvettes, from 1963 up to ?1996, or whatever the prev gen vette, used the half shaft as the upper control arm as well.

From my memory, about 10 yrs ago, at run-n-gun, a contemporary had an exle fail at speed, the back end of the car leaped up, slammed down, ruptured the fuel tank and caught fire. I think it was caused from a faulty weld?

At as autocross, or highway speeds, the failure I would think be more controllable, but at 100+ mph, it could be a problem.

I do know there are thousands of replica's with this rear suspension set up, some of them running more than 700 hp with no failures. Like was said before, make sure you have quality halfshafts and U-joints.

[Gary Essex]

Hi

I have always had a concern with the drive shafts and the function they play with the Jaguar setup. My concerns were realised a few weeks back after playing on the 1/4 mile. One hard launch on a hot day with sticky Avon tyres resulted in a loss of drive when I hit second gear, diff blown was my first thought.

Car was duly towed back to the pits and left for a few hours, while waiting for a recovery truck I tried moving it under its own power and strange as it was it worked. Drove it straight onto the truck when it arrived and off at my destination.

Inspection revealed one drive shaft twisted 45 deg, the other had sheared off completely. Fortunately the sheared one was in a sort of cone shape at the point of shear and the weight of the car pressed the two parts together.

My shafts were from and E Type and not shortened, they have since been replaced with a pair of 2.5inch tubular shafts.

Lucky escape.

[cobrashoch]

Olddog - I too understand your concern with the Jag setup and in my mind it is valid, SORTA. Yes these guys are right, there are few failures reported on the Jag setup, but if that's your only problem with this setup then you can tie off the upper hub with saftety cables to keep the wheel upright if a halfshaft breaks. Another solution would be to to fabricate a upper control arm to the hub or some kind of trailing link. Of course there are other double/wishbone arm setups out there, but that's another thread. My question is this though. Why a Jag setup in the first place? I will repeat what I have said many times and I know this will draw fire. The only advantage ANY independent setup has over a live axle setup is it gives you more suspension travel for when things get really rough. PERIOD! Virturially everything else is compromised a bit with independent setups, from a hot rodders viewpoint. A fact not lost by the NHRA or the SCCA for that matter. So if the ride on your solid axle car is rough, the chances are it is in a overspring condition, or something else is wrong, because even they can be made to both ride soft and perform. Don't forget that Factory Five spec racers use a live rear end setup most times, as does several other sports cars. For further example, the majority of the pro street rods out there use a mono spring setup for heavens sake, and some of those cars are both heavy and have well over 1,000 horsepower.
So my question to the original question is still valid. Why the Jag setup in the first place, over other designs? As with all engineering designs there trades to be made. So you do's your research, pays your moneys, and takes your chances. The Jag setup is relatively inexpensive and has history, but its not perfect.
cobrashock