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"Ever go to do research on something and find your self, smack dab in the middle of a huge debate?? I recently did. I was trying to decide what I wanted to do about the pinion angle on my Jaguar IRS install." |
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| The Jaguar IRS assembly. |
Yet again, "And
finally another update to this web page":
- Page
IV of my Jaguar IRS project was a long time coming and page V
seams to
have taken just as long. It always seams that there is some other
project that is in more urgent need of my attention and so the IRS
install has been continually put on hold. I have recently 04/09/10 been
able to push the IRS install back up to the top of the list and hope to
get it in the car sooner rather than later. In the past I would do the
work and then the web page would follow some months later, but as many
of you have emailed me wanting more information on the final install, I
am going to take a different approach. This page will be a work in
progress; my plan is to update the page as the install goes. When I
rite I like to spend a lot of time rereading the work and laying it out
so it is easy to follow which I will not be able to do until the
install and subsequent web page is finished. Also I am a
horrible
speller, so until the page is finished and finally formatted and edited
after whole thing is done you may find some issues... OK lots of
issues, but I don't think you have been reading this for the spelling
or writing quality.
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04/03/10 The debate over
pinion angle:
- Ever go to
do research on something and find your self, smack dab in the middle of
a huge debate?? I recently did. I was trying to decide what I wanted to
do about the pinion angle on my Jaguar IRS install. There is a
5-degree slope milled in to the top of the differential that could
easily be used to set the pinion at a 5 degree up angle. (perfect since
the T5 in my Mustang hangs down 5 degrees) The cage on a Jaguar IRS
unit however has the opposite 5 degree slope in the differential
mounting
section which cancels out the 5 degree slope on the differential and
sets the differential up with the pinion flange perpendicular to the
ground. I completely understand the importance of setting up the
correct pinion angle but Jaguar had set the system up with 0 degrees
pinion
angle on th XJ6 when there transmission angle is around 3 degrees. This
made me
wonder what others had done: mount it with a pinion angle
parallel to the transmission or
mount it with the pinion flange perpendicular to the ground.
- As I began to read up on the subject I found several long debate threads on several forums. The debate was as heated as the one we in the Mustang community seen between modified and original. One thing I learned is that Jaguar rear ends have been set up both ways and in both types of instelation seams to be working just fine. |
Other
Tech Articles @ www.dazecars.com - Putting
Independant Rear
Susprnsion or IRS in
a classic Mustang
Page
I : Why make
the upgrade and Fords original IRS design
Page II : Where to find a unit, taredown, and cleaning. Page III : Narrowing of the LCAs and half shafts and converting the Jaguar bolt pattern to a Ford bolt pattern. Page IV : The differential rebuild, the drive shaft rebuild, and the rebuilding of the hubs. Page V : Installing the IRS unit in the car -
Retro fitting modern seats in
a classic Mustang
- True ram air ( Thunderbolt style ) - Increasing horsepower "Efficiency -vs- Volume Increases" - performing the UCA drop AKA Shelby Drop, or Arning drop on a classic Mustang, Cougar, or Falcon - Improve Mustang suspension by building a set of Roller Spring Perches - Putting a modern Mustang E-brake handle in a classic Mustang. - Understanding Bump-Steer and eliminating it or reducing it effects. - Suspension 101 Understanding the basic concepts of Mustang Suspension including most of the aftermarket kits and options. - Building a bolt-in spring compressor or ball joint tool. - Fabrication process for building a 9" rear end for a 1964.5-1966 Mustang |
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Roller spring perches T5 Hydraulic Clutch Brackets DIY Roller Spring Perch Master kits Steel UCA Drop Templates 17/32" Drill Bits for UCA Drop CSRP Disc brake kits |
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| Argument for setting up a
matching pinion angle on any rear end IRS or not: The following info was posted by a 34chip on the NSRA forum: First and foremost a universal joint is NOT a constant velocity joint.(this is where the concern lies). this means if its driving a shaft at any angle other than zero, although the half of the joint that is connected to the transmission is rotating at a constant velocity the other half of that same joint is NOT rotating at a constant velocity it is actually constantly accelerating and decelerating on each revolution as the joint is working itself around the angles .at one point it has further to travel because of the angle and so speeds up and at another point it has less distance to travel and so slows down(relative to the trans speed).this means the prop shaft is rotating in a 'jerky 'movement constantly slowing down and speeding up even though the trans is at constant speed .now down at the diff end this 'jerky ' rotation will be transferred to the diff u joint which will be transferred to the wheels so what we would have is the trans trying to drive the wheels at a smooth constant speed but the u joint is trying to slow down and speed up the wheels. this means they are in conflict together causing stress and vibration. the more the angle the worse this 'jerky movement becomes. now to get over this if the diff pinion is set parallel with the trans the half of the u joint at the diff end connected to the diff pinion is also rotating with this 'jerky' movement, slowing down and speeding up each revolution but its equal and opposite to the trans u joint so they cancel each other out and the result is the diff pinion and trans are rotating together at constant speed however the prop shaft is still slowing down and speeding up. twice per rev in fact .if the diff pinion is not set parallel with the trans then this canceling effect does not take place and so the diff will not be rotating at a constant speed in relation to the trans. it is for this reason front wheel drive cars use constant velocity (CV)joints on their driveshafts not u-joints because if you imagine a front wheel on full steering lock the angle of the wheel compared to the drive shaft would be so great this slowing down and speeding up of the wheel joint would be so severe while the drive shaft is trying to go at a constant speed it would shake the whole thing apart instantly. saying all this because the angles we're dealing with are relatively small compared to the front wheel drive scenario if the diff pinion isn’t parallel with the trans then maybe its not noticeable from a driving point of view but this jerky movement is still going on and can cause premature wearing of the joints but as many rods aren’t driven as much as a daily probably not noticeable. - This info is WHY we need to set up the correct pinion angle in any car, but when you point this out to half the individuals who have put an IRS in their car , truck, or hot rod you get one or all of the following replies, with the first one being the most common: "It doesn't apply because the Jaguar differential is hard mounted where as a live axle differential moves up and down with suspension travel" In my opinion this first response is nothing more than something that "sounds good" to try and justify doing it, but really has no bearing on the issue. As the pinion on a live axle moves up and down the angle (in theory) is not changing and the pinion is remaining parallel to the transmission, further more if the road is smooth and the live axle springs are stiff enough the amount of differential movement will be minimal, but you still want the correct pinion angle to prolong u-joint life. "Jaguar didn't do it that way" This second response, I believe, is the main reason this debate has two divided camps. “Jaguar did it that way so it must be right.” To a point I tend to agree with this sort of thinking. Having no formal training in engineering I must trust the designs of those that do, however this argument is in my opinion only completely valid IF AND ONLY IF you set the system up completely as Jaguar designed it, with a cage, with Jaguar cage mounts that have a specific amount of flex designed in to them, with Jaguar trailing arms, and with the transmission angle at 3 degrees down. The more of these thins you change, the argument “that’s the way Jaguar did it” becomes less and less valid as you are not setting it up the Jaguar did. Coupled in with this, as hot rodders copied the way Jaguar did it, and then helped others do the same thing they said “this is how I did it and it works just fine” "The lower control arms (wishbones) on a Jaguar IRS are perpendicular to the pinion flange so mounting the diff at 0 degrees pinion angle allows the suspension to move perpendicular to the road. If you set the pinion at an angle the wishbones will also be at an angle and move backwards as the suspension compresses.” This third argument seams to me to have the most validity, and I speculate is the reason that Jaguar did things the way they did. If the pinion is perpendicular to the ground the wheels will stay centered in the wheel well, and all forces will be applied vertically. All that said I do not see , with only being 5 degrees off of perpendicular, that there would be that big of an issue. I did a little math and with a 5-degree angle on the wishbones 3” of suspension travel would only result in .262” of backward movement at the wheel. A leaf spring set up moves the wheel backwards at least that much as the spring compresses so I fail to see the issue. With all this in mind I have decided to match the the pinion angle to the angle of the transmission. I feel that u-joint life and reduction in vibration is mor eimportant than the wishbones moving perfectly virtical to the road. If I really thought the angle of the wishbones was a problem, I could order side brackets from CWI that allow you to return the suspension travel to vertical even if the pinion angle is different. They are $200 for a pare but only come in 3 and 6 degree angles. It's all about cost benefit. I have enough $$ in this project that if I thought it would make that much difference I would pony up, but I just don't think it will be that much of an issue. |
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04/08/10 Taking measurements
and Leveling the Car:
- Prior to removing the old system, it is a really good idea to take measurements of how all the OEM suspension parts are positioned. Also taking many digital photos is an added point of reference, should you find you need it during the IRS install. This will give you a relatively good idea of where the IRS components need to be placed in relationship to the rest of the car based on the location of the original suspension. - A tape measure, level, angle finder, and note pad and pencil will be needed to take and then record all the measurements. The basic measurements like distance from the top of the differential to the underside of the car, distance from the axle tubes to the under side of the car, wheels in relationship to the fenders, axle tube in relation to the front leaf spring bolts and any other dimensional measurements can be taken using a tape measure. NOTE make sure all measurements are taken based on a fixed location in the car that will remain intact after the rear suspension has been removed.
- To accurately record all these measurements it is a good idea to draw out a picture and then write down all these measurements on said picture. You may find that there is a slight variation from one side of the car to the other, and if this is the case determine if it is a result of the components being misaligned or if it is something on the actual car that would need to be addressed prior to the install of the IRS unit, such as a bent frame rail. - In order to accurately take measurement of things like pinion angle and transmission angle, it is a really good idea to level up the car. This step is not necessary as you can figure out pinion angle by measuring said angle and then measuring the angle of the cars stance than using the two angles to do a simple calculation, however, by leveling up the car you eliminate the need for calculations. With the car level, you can simply measure at the pinion or transmission. This is not only important during the initial measuring but will also need to be kept in mind once the actual install begins. Having a level car as you fabricate pieces will make it easier to get said pieces correctly positioned. - Prior to being able to level your car you must find a place on the car that would be level if the ride height was the same at both the front and rear wheels. On a mustang the rocker panel offers several locations that this criteria applies to: the pinch welds just under the rocker panel, the flat area next to the pinch welds on the underside of the rocker panel as well as the top of the rocker panel when the door is open and the scuff plate is removed. Keep in mind that any surface imperfections can make all of these places less accurate. There may be adhesive on the top of the rocker panel where the scuff plate was, or the spot welds on the pinch weld may make the lower edge uneven.
- Keep such imperfections in mind and eliminate theses issues as best as possible. A good example would be to scrape the adhesive off of the rocker panel. Another way to help eliminate issues caused by imperfections in the rocker panel is take lots of measurements from lots of different areas, using several different measuring tools. The more information you collect the better opportunity you have to make sure you have the car as close to level as possible. I used several levels and my angle finder to get my car correctly orientated. After each measurement, to actually adjust of the cars stance and level it up I simply let a little air out of the tires, took more measurements and then repeated the process until I had the car level. NOTE Keep in mind the car needs to be level in all directions, not just front to back. - Once I had the car level I was able to use the angle finder to check pinion angle at the differential and more importantly the angle of the transmission. As talked about in great detail above, the transmission angle is critically important to achieve the correct pinion angle on the IRS unit for the purpose of insuring long u-joint life. In order to measure my transmission angle I used an old slip yoke that had an inner surface that was perpendicular to the mane shaft of the yoke. To get it truly perpendicular I had to lightly run a file over the surface to remove a bur. With the yoke in place I was able to take the measurement and found that the T5 transmission in my car hangs down at an angle of five degrees. 4/12/10 removing the OEM parts : - There is not a lot of technical skill needed to remove the OEM parts. There are however a few things to keep in mind prior to the removal of the parts. First penetrating oil is your friend!!! Several days before I removed the rear end, shocks, and leaf springs from my car, I applied liberal amounts of penetrating oil to all the bolts and nuts that would need to be removed. This step was done many times and made the removal easier, but I still had some difficulty removing the nuts from the u-bolts on the underside of the leaf springs. - The other thing to consider is make sure the car is solidly supported so that the rear end parts can be safely removed. To accomplish this I placed jack stands under the rear pinch weld at the jacking notch as well as a cross support under my sub frame connectors. Supporting the car at just the pinch weld or at just the sub frame connectors probably would have worked, but there is no reason to support the car in just one location if you can support it in several. This will add extra stability, and in turn make working under the car safer. With these simple things in mind I was able to easily get all the old parts out and take a good hard look at what I would need to fabricate to install this unit. My plan has always been to make this install a complete bolt in and with all the original parts out of the car I was able to confirm that this plan will be easily attainable. 4/14/10 Why make it a bolt in? - There are lots of reasons. Will I ever remove this set up and go back to OEM equipment?? Probably not, than why make it a bolt on?? Well it’s like this: - First, some day the car will no longer be mine. Hopefully that won't be for another 50-70 years, but the reality is some day I will be dead and gone and the car will hopefully belong to my daughter or one of her kids. With that in mind, even though I love to modify things I try to make all my modifications easily undoable. This way if I change my mind in the future or some future owner wants to do something different they easily can. - Second, Ford did it that way. The IRS Ford designed for the Mustang was built with the idea of it being a dealer added bolt on and even though my install will not be exactly the same, in as many ways as possible I am trying to emulate that original design - Third, and this is a big one, strength. The rear frame rails on a Mustang are way to thin IMHO. If I weld mounting brackets on to the frame that would put a lot of stress on the middle section of the frame, and more specifically on the thin frame walls. I know the weight of the, back half of the car can easily be supported by the leaf spring mounting locations so I want my set up to attach there - Forth, mounting bushings. As you know Jaguar put all the parts in a self contained cage and then used rubber bushings to mount said cage to the car. By using the stock leaf spring mounting locations I can easily use leaf spring bushings to accomplish the same thing. Leaf spring bushings are durable, easy to find, availably in several different materials depending on desired stiffness, and will work well in isolating the mounting frame from the chassis. - Fifth, I like a challenge… enough said 04/14/10 Building a pattern for the side mounts: NOTE prior to beginning the fabrication phase of the install make sure the car is still level. Changes in the weight of the rear half of the car may cause the front suspension to shift and the car may need to be re-leveled. In fact it is a really good idea to make sure the car is still level at the beginning of each and every work session. - As I said above, this install will be a bolt on utilizing the original leaf spring mounting locations to attach my IRS support system to the car. To accomplish this I needed to make a frame that bolts in said location and runs along the curves of the original frame rails. Rather than start with the actual material I will be using for said supports, I decided to make a pattern using some .75" X 1.5" tubing with 18 gage walls as it was scrap I had laying around, was easy to work with and was light. - As I started to build the patter, I relied on my tape measure, and trial and error to come up with the correct angles. After about an hour I realized that I could easily get the angles I needed by using my angle finder in the mustangs frame rails. With an accurate way to measure the frame the piece came together quickly. - As you can see it fits well and the design provides a nice level center section to weld in tubes that will connect the two brackets together. From there I can hang the Jaguar parts from the cross tubes. - The pattern will be used to make the final units out of 1.5" X 2" rectangular tubing with .120 walls. As I was building the pattern I was trying to decide weather to notch the tubing, bend it, then weld it back together my self, or have it bent, at a local shop. Even though the bent tube would probably be cleaner I decided I want to keep this a DIY as possible so I will use the notch and weld method, besides then it will match my sub frame connectors. |
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