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daring to be different rear axle thread

4K views 24 replies 18 participants last post by  smokepedal 
#1 ·
Hi guys, this my first post on the hotrodders forum. I am a member of performanceyears, dieseltruckresource, and dieselplace, so this isn't my first go round being the new guy. I am posting this because I am a little tired of the pontiac only guys, and the closed minded attitude I see over at performanceyears. I am not trying to knock that site, because it has it's niche, it's just that there is a wider sampling of gear heads over here, and that is kind of what I am into.

Here is the deal, I am building my 72 pontiac Lemans into a resto-mod, and with that in mind, I just wanted to get your opinion on my newest hairbrained idea for a rear axle. I want to put a Jaguar jag for search's sake rear axle in my full size cruiser.

The center section is a Dana 44, with a few minor differences to the american version. It has inboard disc brakes, with parking brakes. A dana 44 is as strong as a 12 bolt as far as I can tell, with the exception of the smaller pinion shaft inthe Jag model. I suppose there are some weak points to be afraid of, but I don't think this would be a bad way to go.

My reason for going with this is, when you launch with a normal rear axle, the driver's side tire always tries to plant harder than the passenger's side tire. this is due to driveline torque. With an independent suspension, the torque is transmitted to the frame, and only the torque going with the direction of the tires is transmitted to them. the other deal is a lot of the jag rear ends came with posi, all of them came with disc brakes, and they were mostly in the 3.05 to 3.50 ratio neighborhood. This means I don't have to have axles made, buy a disc brake setup, buy a 9 inch housing or a 12 bolt housing, probably change the gears... I have found like 3 of the jag rearends complete for less than 500 within 50 miles of me. I can fab up the mounts for the axle, and get it set up.

Dealing with my p.o.s. b.o.p 8.2 inch open drum brake rear is out of the question with 450 hp, and about 550 torque.
 
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#2 ·
Most tame the torque transfer problem with an airbag inside the right coil spring. The Jag rear will be alot of work but is do able. Have you thought about an 8.5" 10 Bolt from another car such as Chevelle or Buick GN/T-type, Olds H/O,442? Those are almost as strong as a 12 Bolt. Should find tons of Jag rear Info here.>> http://www.jagsthatrun.com/
 

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#3 ·
I put a Jag in my T-bucket last year after running it for a couple of years with a straight axle. I really like the Jag, very tunable for ride height and ride quality. I don't have posi, but both sides hook well without it. I always leave two stripes on burn-outs! :thumbup:

Are you thinking you will use the stock cage to mount the rear-end in your Poncho? That would be the simplest way to preserve the geometry, which is critical in setting up the Jag. If you mess up the alignment of the various swing axes (plural of axis), you will get binding and a harsh ride, and you'll wear out the bearings in the trunions very quickly. Alignment of the trailing arms (radius rods) is critical also, for the same reason.

The weak links in the Jag are the half-shafts. Supposedly only good for about 300 hp/ft.lb. in a heavy car. You can get aftermarket parts that will handle a lot more power. Here's one possible source... Concourse West Industries

Last comment about Jags... nothing about them is cheap! :pain:
 
#4 ·
The center sections are pretty beefy, but nothing to write home about. They're more on par with the strength of an 8.5". XNTRCI-T is right... the shafts and U-joints are the weak part but that can be fixed.

The Corvette C4 uses a sorta D40/D44 hybrid that has been shown to work well with sticky tires and medium weight cars, but then you're paying 'vette prices.

The Jag is a well-used IRS. You might want to contact Heidt's. They do a lot of this type of thing for rods.

The IRS will have a tougher time planting the torque. The independent travel will make tuning the launch a good bit more difficult than a solid axle, but if you get it sorted out it will be worth it. :)

Good for you... thinking outside the "poncho" box. I have a 66 Bonneville with a 14 bolt FF axle, 3/4 ton front spindles and brakes on modified custom arms, and a Caddy 500 under the hood. Its soon getting either a Duramax or a V10 TDI.
 

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#5 ·
halfshafts

I looked at the halfshafts, and they did look a little spindly. I was comparing them to axleshafts in my mind, and they didn't seem to be much smaller than regular axle shafts, so until you mentioned that, I wasn't too worried. I suppose they could be a weaker alloy. The corvette rears are going for at least 1,000 and I can get the jags for next to nothing. I can have halfshafts built at a driveline place for around 300 /pair. I did intend to use the stock cage on the rearend, and work it into my frame. I also wanted the jag because it looked a little less complicated than the corvette.

you don't have to tell me about how expensive jags are, because it cost about 450 when I lost the key for my wife's car. she has an 04 x-type. it is a pretty snappy car, but I am not looking forward to replacing parts on it. I had to take the intake manifold off to change the spark plugs, but I suppose that ins't too bad considering some of the abhorrations gm has made as far as maintenance goes.
 
#6 ·
traction

I realize taht you can compensate for the torque on the axle by adding a air bag to the passenger's side, but that puts more pressure on the front left, and right rear tire under all conditions other than a hard launch. A properly set up car should at least try to keep even pressure on all tires, and not just during launch. I realize that you can't set up the rear end to plant harder under the shock of launch, but I am okay with that. I intend to limit the stress on the axle, and instead be hard on tires. I will probably run with 245-40-16 tires or 265-35-16 radial tires. this is a fun cruiser, not a drag car. those tend to be more work than fun, and also I am not going to be able to compete with the extreme guys with only 450 hp, and no more than 500 in the future of this car.
 
#7 ·
I just wonder what the weight of that Lemans compared to the jag. should work out and be different..As far as launch is concerned there is a reason that serious quarter milers stick to a solid rear but for a driver the gains in handling make a lot of sense..

Sam
 
#9 · (Edited)
Just to throw another option out there....I'm planning on an R200 and stock half shafts from an old Datsun + coil overs in my upcoming setup. (or an R230, if I can find one at a decent $$$. R230 has VLSD already installed.) Plus, I believe there is more of an aftermarket for it.

Independent and will easily take 700-800ft/lbs in stock trim. There's a video floating around for a drag guy in NZ using a stock longnose R200 in his 8 second/900hp Z-car.

OF course, a straight axle would be easier...especially for your application...but just throwin' that out there. :thumbup:
 
#11 ·
You might want to try a rear sway/anti roll bar before you go to the Jag. There are several after market ones available and these can really help. The car may over steer a bit but they under steer a lot to begin with so it should help this too.

You will probably need one anyway.
 
#12 ·
I am pretty much sold on the independent suspension, but not necessarily the Jag. I can find some corvette rears as well, and some of them have the dana 44 center section as well. I have a lead on one right now, but don't know how to tell if it is the weaker dana center. I do like the thought of the axleshafts being larger hollow tubes, rather than solid shafts. I have to do some research right now, but I will let you guys know what I decide to do.

Mike

The weaker dana is a 36 right? Whatever, I will figure it out.
 
#13 ·
First off, welcome to the site. Second, "not a drag car. those tend to be more work than fun," that depends on how you look at it. And finally, "I am not going to be able to compete with the extreme guys with only 450 hp, and no more than 500 in the future of this car." I've seen high 11 second door cars beat 7 second dragsters in a bracket race. It all depends on what you want to do, but to me there's no bigger thrill than a tight race.

Bill

 
#14 ·
Just my $0.02.

A properly set up 4 link with a 9 inch is what you want for a drag car.

The IRS advantage is the decrease in unsprung weight. This is a handling issue. Unsprung weight is dead weight. It doesn't "work" the suspension. But even then, Carroll Shelby could have gone IRS on the Cobra, but didn't.

My understanding is that you can't beat the feel of an IRS on the street.

Long story short IMHO, Street car - use an IRS if you can afford it. Track (with turns) car - try an IRS if you can afford it and the rules permit, but you may be disappointed. Drag car - 4 link with a 9 inch (or a Dana - or a 12 bolt - etc.)
 
#15 ·
I think you are overestimating the benefit of an IRS. Check out Club Cobra for input on IRS and drag racing( several Cobra kits are based around Jag IRS), it's not all you think...a solid axle will be stronger and better. The main advantage of any IRS is ride quality...it's not traction under drag racing conditions...look at how many IRS drag cars there are... I would venture only the ones required to maintain their stock ones under the rules. In a lightweight T-bucket they offer a better ride, but in a heavier vehicle I think you'll find that you have spent a lot of money and time for a step backwards.
That excludes the fact that the brake calipers are prone to seizing up after time, the brake pads are a pain to change and the discs are solid and close to the center section so run hotter because they get little air flow, meaning more frequent pad changes.I am speaking from experience with Jags, which are similar in weight to what you are building. They were popular at one time under T's because they looked really good from the rear and improved ride quality( you are setting almost on the rear axle in one).
In the 60s, they were considering putting an IRS under the GT350, even built a prototype or 2. It showed no signicant improvement in lap times over the solid axle, although it may have had a better ride.
 
#16 ·
mycarisfaster455 said:
I am pretty much sold on the independent suspension, but not necessarily the Jag. I can find some corvette rears as well, and some of them have the dana 44 center section as well. I have a lead on one right now, but don't know how to tell if it is the weaker dana center. I do like the thought of the axleshafts being larger hollow tubes, rather than solid shafts. I have to do some research right now, but I will let you guys know what I decide to do.

Mike

The weaker dana is a 36 right? Whatever, I will figure it out.

all manual transmission corvettes came with the danna 44
I'd go with the c4 IRS unit if you can figure out how to do the fabrication
 
#17 ·
I did it.

I bought a Jag rear with 3.05 gears and posi. It was out of an 87 xj12 and the track width is perfect. The axleshafts are about 1 1/4" thick, so I don't think they will break. I found out they are forged steel shafts too. I mounted it with no problems. I had to move the frame mounts out about 3/4 inch each side.
I took the trailing arm mounts off the donor car, and everything looks like it was designed to fit right in my Pontiac. I didn't have a driveline made yet, because there are too many other irons in the fire right now. I did use a conversion u-joint to go between the two styles, and hopefully it will be strong enough. I don't think I will have enough traction with 245 tires to break anything. The only people I have heard of blowing these up are running blown engines and 18 inch wide radial tires. I will have some pics up soon.
 
#19 ·
Actually, it is not planting the right rear. The car is trying to rotate the right rear into the wheel well. Someone makes a bracket that adjusts the mounting point to correct the four-link. I have a Moser 9" that has the correct geometry built in. Launches like a dream.

Rick
 
#20 ·
two things,
first I am north of san diego about 30 miles in oceanside.

second, you are right about lifting up on right rear and planting left rear. I had my directions mixed up.
If you think about it, preloading the right rear spring slightly stiffer such as with adjustable coilovers will help with traction in a high driveshaft torque situation, but in the inverse when you are hitting the brakes, you will not have the same weight on the left rear and the right front as the left front and right rear. it works great for drag racing, but the IRS is better for street use. It rides nicer, and is just cool, so I did it.

I bought the whole rear end and mounted it for under $600. If I wanted to put a strong straight axle with posi and disc brakes in my car I would be easily over 1500. I would also have to get better control arm bushings, beef up the lower control arms and after all that work, I would have the same axle everybody else has.
 
#22 ·
dude that 66 bonneville with a 14 FF 10.5" under it wow very cool i have never seen a 14 FF under a car ever until now haha thats great

is it narrowed or anything ?

ive owned alot of 3/4 and 1 ton trucks with the 10.5" axle but under a car thats just so odd looking but cool lol :evil:
 
#23 ·
jag irs

the irs can handle more than 300hp/lb the standard xjr-s v12 was 333hp and twr and lister tuned the v12 to 500hp with torque to match and they all used the standard irs rear end.
Its not actually a Dana 44 its a Salisbury, it has some small differences to the Dana 44 the ring gears have larger bolts and the yoke is smaller but dana 44 stuff can be made to fit. Jag did use the dana 44 for 2 year i think 86-88 it was is ment to be weaker but i don't know for sure

could a Detroit locker for the dana? fit has anyone had any experience with this set up i know the jeep guys use them

check out www.jag-lovers.org it has lots of info on the jag rearend
 
#24 ·
Yeah, this rear end is out of a 87 xj6. So I am pretty sure I have the Dana 44. They call it a Salisbury to differentiate it from a standard Dana 44. That name comes from the Dana plant in Salisbury England.

I have it in the car now and love it. I will post some pics when I get a chance.
 
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