Rear end ratings.

[chrispy]

Does anyone know of an independent source for ratings on rear ends. Specifically the fords 8.8 inch 9 inch, and the Dana 44 that is in the Jaguar IRS. What kind of torque and HP does each handle.

Came across the Everett Morrison that has an IRS based on the 8.8 inch. At 6' 4" the EM intrigues me with the 3" extra leg room (hate to look like an idiot sitting so high). The 8.8 inch does worry me though. I am sure that the weak link in an 8.8 inch IRS rear is not the pumpkin, but the CV joints, but would like to hear from anyone that is running it.

If I remember correctly the Dana 44 and the ford 9" pumpkins are about the same rating. And I have heard that the Jag IRS weak link is the half shafts. I am also looking at the ERA kit with the Jag IRS and they seem to of beefed up the half shafts, but am still curious as to the HP they can REALLY handle. Heck ERA has the twin Paxton machine out there. I wonder how the Jag IRS is handling it.

Also would like anyone to comment on the Everett Morrison kit. Off the top of my head and not crunching the numbers, it does seem a little pricey. I am sure that it is worth it, but would like to hear from others.

Thanks,
Chris

[Excaliber]

One of the main advantages of a replica is it's relative light weight compared to other cars. Because of this single factor the read end components are NOT subject to the typical stress factors you would see on a standard issue "car". Traction loss usually comes WELL before any serious stress loads are seen.

Now if you want to go dracing with sticky slicks and ultra low rear gearing there is no question which is strongest, Ford 9", end of story! But the 289 and 427 cars, drag or road race, ran well with the original style (Jaguar like in specs) rear suspension. The full blown "drag race" only Cobras had the rear gears heat treated for additional strength and they DID want to run a solid axle (like Ford 9") but Shelby would not allow it. Bear in mind these cars ran gearing like 5:13 to 1 rear ratio and massive slicks!

ERA's approach to strengthening of the half shafts makes them pretty darn bullet proof! I have heard of CV joint failures on other IRS systems, but I would not conclude that is because of excess stress levels (high horse power). It seems to be more about "quality" control and defective parts or installation rather than "broken" parts.

[chrispy]

Excaliber,

Thanks for the insight, very helpful. You did bring it to my attention that we are not launching a 2 ton car, something that I was not considering. I guess we can say that the light weight and the subsequent loss of traction, saves the rear-end.

I am assuming that the Jag IRS has the 8.5" ring gear in the Dana pumpkin. Comparing that to the 8.8" ford I guess they should be the same. Your mention of the heat treating of the gears, makes me think that this is the weak-point. Not too bad.

Like you mentioned "quality". I wonder how strong/quality the Everett Morrison IRS is compared to the JAG IRS setup from ERA?????

Than again as I read through, and do my research, I do not see many people having rear-end problems. Including some of the larger HP Cobras out there. So is it safe to assume that running say 800hp to a IRS (either the 8" or JAG) should not be a problem???

Thanks again,
Chris

[HighPlainsDrifter]

Hi,
You should email Double Venom, he has been there and broken everything so he can tell you what will work.
Good Luck,
Perry.

[chrispy]

Highplains,

Hopefully he has broken a few rear-ends as well.

[Excaliber]

Ha ha,,,oh yeah Ed with his Viper powered V-10 Classic Roadster running LOW rear gears at the drag strip is the KING of breaking them. He's toasted a couple of Ford 9", made 'em look like pretzels! Is that possible?

[427sharpe]

The 8.8 has plenty of parts and pro's out there to make it darn near bullet proof. Witness all the 5.0 Mustangs running sub-10 sec 1/4 miles..with 8.8 rears. The 8.8's big advantage over the other rears you mention..esp the 9"..is efficiency. The 8.8 draws a lot less power out of the motor than any of the others. For sources, pick up any of the magazines that cater to the 5.0 crowd. To simplify, call or check out Currie Enterprises. They are probably the premier differential builder going for retail use.

[Anthony]

Originally posted by chrispy
Does anyone know of an independent source for ratings on rear ends. Specifically the fords 8.8 inch 9 inch, and the Dana 44 that is in the Jaguar IRS. What kind of torque and HP does each handle.

I think the hp/torque rating of rears is primarily a function of ring gear diameter, the larger the radius/diameter, the more torque it can handle. Dana 44 is 8.5", which is what's in vipers. Chevy 12 bolt I think is 8.875". I think a Dana 60 is about 9 1/2", which is what was in hemi cars.

They're all strong enough.

[chrispy]

So I guess the general thought is that either the Jag Dana 44 IRS, and the EM 8" IRS should not really be a concern.

I think that Excaliber corrected me. I had totally forgotten to factor in the weight. With the Cobra being so less, it really helps with my concerns.

Although I would love to hear from someone that has used the EM IRS behind some serious power. It does seem to me that the ERA IRS has already been proven.

Thanks again all,
Chris

[cobrashoch]

Actually they are all pretty close in ratings in both the aftermarket, or as stock, with the exception of the 9 inch Ford and the Dana 60. The ring gear diameter affects ring and pinion gear wear, because as the ratio goes up, there is more gears and they get finer on the ring. So as the ratio goes up they also have to spin faster. A 4.10 ratio is marginal in all 8.8's for ring gear wear, and ratios past 4.88's are marginal on 9 inch Fords. You can slap anything into a dana 60's 9 3/4 inch ring gear rear end and not even think about ring gear wear.
Of course most guys in lightweight Cobras don't run ratio's past 3.91's so by in large the common 8.8's pig size in most makes, to include the Dana 44 and the Jag is not the problem for a Cobra. At least as in how strong they are. Just remember that generally the larger the ring gear the larger and stronger the guts are in the rear end. And larger usially has more weight too.

But the axle size in rear ends is a BIG problem, togeter with half shaft weakness in ALL, I repeat,,, -- ALL--,, independent rear ends. But that's another topic for another time.
cobrashock

[Excaliber]

Good points Ron. As far as ring gear wear goes I don't think thats an issue with the few miles most of us put on our replicas.

[cobrashoch]

Slick - awwwwwwwww, but it is in reality a factor, at least indirectly. We are talking rear end noise, heat buildup, loss of tranferred power(power soak) just to name a few. All is not in as you percieve things when hot rodding stuff. For example I don't believe a Detroit soft locker is available for a Jag rear end yet. Even if it is out there, you get the idea I think.
cobrashock

[CJ428CJ]

I don't think the Dana 44 used in the Jag rearend is as strong as some might lead you to believe. I've had no problems with mine but Decooney and ERA626 both blew there Dana 44's within just a few months of getting their cars on the road. I think they both tore up the spider gears and twisted the stub axles. So much for breaking the tires loose before anything else breaks. I'm sure they'd both give you some recommendations as to what you need to do to make these rearends stronger.

Chris

[cobrashoch]

Chis - Make me wonder out loud if they did anything to help them
or if they were bone stock when they blew. Dana 44's are a staple in the 4-wheel drive crowd, and some of those guys run 600 cuber blown alcohol engines. Still, as they say, you generally get what you pay for. Maybe their more expensive second experiences with those rear ends are more representative of their potental you think?
cobrashock

[Anthony]

Originally posted by CJ428CJ
I don't think the Dana 44 used in the Jag rearend is as strong as some might lead you to believe. I've had no problems with mine but Decooney and ERA626 both blew there Dana 44's within just a few months of getting their cars on the road. I think they both tore up the spider gears and twisted the stub axles. So much for breaking the tires loose before anything else breaks. I'm sure they'd both give you some recommendations as to what you need to do to make these rearends stronger.

The differential is another story, not necessarily as strong as the ring/pinion gears. I think the differential's vary alot in durability/strength, as opposed to the gears themselves , which thickness/size is determined by its designed location with respect to each other.

[RICK LAKE]

Chris here we go again. What are you going to do with the car? How much power are you putting under the hood? Trans mission? I jag rear will take about 450hp ERA makes stronger half shafts for there rearends. Chromemoly tubing. If you are going for 600hp go to 30 spline stub shafts, Mark Williams makes them, Detroit locker for the rear and a rear cover gridle to help the caps stay in place. Tires? what size are you running and how soft? No rear is going to last with 5000 rpm hole shots. There are cars with 800 hp out there and the rears hold up OK but are check on a regular maintainance check. Change the fluid and look for metal chips. 9" rear is stronger with ahousing support welded to the back. 35-40 spline axles can be gotten. Larger bearings can take more stress. Have you looked into a quick change rear like a Franklin that dirt track drivers use? This has a 9" ring and pininion, IRS setup for better handling and is good for 750hp. Fill in the blanks and we will see what we can do. Gear ratio? Rick Lake ps I bring a spare jag rear when I race, trans too. Have not needed either yet.

[chrispy]

Rick,
I assume that your Jag rear end is holding up?

Mind you I am still in the planning stage at the moment. Lot more details to work out than I thought. But it is fun, albeit costing me more ever turn.

I definitely am leaning towards an IRS kit. The ERA intrigues me the most at the moment. Although the EM is becoming interesting as well. Mostly street driven, occasional drag, or circle, but not much. I am looking at something similar as Rick's setup. Alum 427, stack injection, and supercharged.

Tranny I have not figured out yet. Of course the top loader would be ideal, but I am leaning towards a 5 or 6 speed thanks to the gas prices. Same with gear ratio. Working on that soon, but it would be in the streetable range.

800hp might be way on the high side, but seeing that KC just got 710hp out of a similar setup without the charger...... I figure I would play it safe and call it 800. Street tires BTW.

With the kit cars for example, it would be hard to beef up the rear end as they are included in the kits. Than again, maybe not, and this is something that I should look into further.

I have looked at other IRS rear ends, not only are they costly they also would need to be customized as well as the chassis that it is going into. Something that I am not looking forward to doing.

Hope that answers all of it.

[427sharpe]

Actually, one of the most important things in determining strength is the pinion ratio or how high or low the pinion rides on the ring gear. This is what makes the 9" so strong...and also what makes it soak horsepower. As for durability, there is a reason why the 9" is still the top rear end...BRUTE STRENGTH and balls on reliability. NASCAR anyone? Still using 9" rearends basically lifted from a '65 Galaxie (layout) and still never breaking one. Gearsets are still plentiful and reasonably priced and the diff is very easy to set up. Not bad for a rear end that last saw a production line over 20 years ago. I would say if a solid axle is the choice and you want reliabilty behind a lot of torque and in front of slicks, the 9 is the way to go. If you are a cruiser that will see ocassional track, the 8.8. In IRS, I have built a number of setups for all kinds of cars, and the 8.8 has been excellent. In a Cobra, I would say that the differential mounting would be the most imnportant factor, as the TBird diff has relatively weak mountings. If you go the 8.8 road, use an Explorer diff and axles, as they are much stouter than TBird/Cougar/Mk VIII. A big plus, parts are readily available anywhere, and practically any full service garage can fix a problem...can't be said of Jag stuff.

[hoppy]

Originally posted by RICK LAKE


[ I jag rear will take about 450hp ERA makes stronger half shafts for there rearends. Chromemoly tubing. If you are going for 600hp go to 30 spline stub shafts, Mark Williams makes them, Detroit locker for the rear and a rear cover gridle to help the caps stay in place. [/b]

If you have a lot of torque you will definatly want the Mark Williams 30 spline stub axels. I just had my suspension worked over by Tom Barnard and when he found the rear seals leaking and had the diff. taken apart the stock stub axels (Jag IRS) were twisted and bent. This is from a relatively mild 428SCJ. It's an expensive fix but cheap insurance compared to shearing one off.

[Excaliber]

800 horse on "street" tires aint gonna cut it. You'll need Yokohama Auto X tires, BIG letter bias Goodyears (thats what I run), Eagle F1 or similiar. OK call 'em "street" but they better be awesome.

With 800 horse I'd lean toward a straight axle all right, a Ford 9" to be specific. But the ride is SO much better with IRS, I can understand wanting your cake and eating it too.

Rear gear ratios:
With that kind of horse I would go with a HIGH rear gear, like the typical 3:31 ratio common to Jag IRS units. It's just much easier to "control" horse power with a higher gear set AND you GOT to have great traction as well! But with the high rear gear NOW you got a problem with that 5th or 6th gear Overdrive. Shooting for 800 horse means you gonna have a NASTY cam and turning 6500 rpm or so. The motor is NOT going to like highway "cruising" at the lower Overdrive rpm range (unless your hauling ass).

Yeah, you got to work out the details in a number of areas. The cam selection is CRITICAL to overall drivability. The rear gear in large part should "drive" the cam selection. The BIG horse power will soon enough FORCE you to seriously consider the right tires. The trans gearing needs to be worked out. What you DON'T want is 1st gear so freakin' low it's a joke and unusable. That happens a LOT.