on May 25, 2010, 8:23 am, Daze wrote:

You are correct that the diff being offset added to the complication of setting pinion angle, but not if the diff and trans are both parallel to the car and thus parallel to each other. I once herd a guy say, when looking at this exact problem that "with the pinion being offset you will have problems even if the pinion and trans angles are parallel because u-joints don't like multiple angles" At the time it struck me as kind of odd because the the driveline only sees one angle which is a combination of the angles and the distance between the parallels. Make sense?? (assuming no limitation on u-joint bends) It doesn't matter where the transmission and pinion are located in relation to each other as long as they are parallel on ALL planes. For two u-joints to cancel each other out they must be opposite angles at all times and as long as the transmission and pinion are both parallel with the car, and set at parallel angles then there over all angles will be opposite and cancel each other out. This is a tall order as most Mustang dont allow the transmission to be parallel with the car. I tried for years to square mine up and was not able to do it until I got adjustable engine mounts and now it lines up perfect.

In this case my over thinking, and the part I would like your thoughts on (I do appreciate your thoughts on pinion angle) is weather the suspension should travel perfectly vertical or if there would be any problem with it having a few degrees of positive caster. Other then the wheel moving slightly back during suspension travel I don't think it will be a problem, but I am still striving for perfection

on August 16, 2010, 4:20 am, tyrellracing wrote:

Ideally you always want the center line of the crank/transmission to be at a complimentary angle to the center line of the pinion so when viewed from the side and viewed from above these lines will be parallel. With these planes of rotation parallel and a balanced drive shaft there will be no measurable vibration. Any deviation from this will generate vibration. Passenger cars are for the comparison are light and use a drive shaft that is proportionally light so the vibrations created by 1,2 or 3 degrees of misalignment will be absorbed by the mass of the rear end housing and/or the mass of the trans/engine. This does not mean the vibration does not exist it is just nullified by pounding on parts with enough mass and strong enough anchorage that the driver cannot feel it. Now when we place a semi in this same scenario. The 50 lbs added weight to the drive shafts create vibration so bad at 2or3 degrees of misalignment that ring and pinions can be destroyed and transmissions can have gears friction weld them self's to the journals they ride on. At 5 degrees or more misalignment, things come apart violently. period. If you install the Jag dif too far off the correct angle and have some vibration, try installing a aluminum drive shaft. The reduced mass will hide a world of misalignment. All the manufactures know this fact all too well so when you find a factory setup that was built out of alignment by 3 degrees or more and no double cardan joint, it is either sloppy work or they determined that the parts being pounded on were strong enough to survive to the end of the factory warranty. I took a class provided by Spicer years ago and this is what was taught. I think you can still find proof of this somewhere in their website.

on August 17, 2010, 12:10 am,  tyrellracing wrote:

The primary reason the OEM's started using aluminum drive shafts is to comply with federally mandated fuel mileage limits. The less weight in your drive train the less HP required to turn it. all items hat rotate at crank shaft speed have the most drag on power. overdrive transmissions rotate the drive shaft faster than crank speed making it a serious threat to gas mileage. This is why the OEM's use aluminum drive shafts. One enormous draw back is the critical speed and fatigue strength. goto go more later

on August 17, 2010, 3:00 am,  tyrellracing wrote:

Sorry about the typo's Critical speed of a drive shaft is the relation between the two factors of drive shaft design. This is only the fundamentals. The diameter of tube v.s. length. The longer the drive shaft the larger the tube must be. All drive shafts will begin to vibrate like a guitar string with high enough rpm's. If rpm's continue to climb the vibration will be followed by catastrophic failure.The test videos Spicer played had about 10 examples of critical speed failure. The high rpms combined with the harmonic vibration creates an instability in the center of the shaft that can only be described as a fragmentary explosion. The point where the harmonic vibrations begin is the critical speed. This is not due to an imbalance it is a by product of the tube drive shaft design. The longer the length, smaller the dia. the lower the critical speed. Shorter length and larger tube dia. the higher critical speed. The rpms required for critical speed are much lower than most people are aware. I have a drive shaft calculator made by spicer so I will throw out a few common sizes and diameters. These speeds are the highest speeds spicer recommends these slip yoke type shafts be run: A 3 inch dia,50 inch long shaft has a cs of 4800 rpms. A 4 inch dia,50 long has a cs of 5800 rpms I use a 3 inch dia.48 long shaft with a cs of 4800 rpms. Get this, my engine has a red line of 7500 rpms and a overdrive trans and have had it up to 184 mph. I know this seems like a red herring but steel has a much higher fatigue strength than aluminum and my drive shaft had to have been doing some wild things at 184. Aluminum would not have made it on that run. Aluminum work hardens so easy that 10 or so trips above cs would harden the tube enough to start a crack. The OEM's know this and in applications where they know they will go beyond cs and still use an aluminum shaft they will use a carbon fiber reinforcement tube bonded to the outside of the aluminum tube. This combination works better than steel in cs performance. On PU. trucks with aluminum shafts they will use a very large dia tube (6+ dia)to combat cs. This dia is impractical for any app but trucks.

on May 26, 2010, 8:14 am, Daze wrote:

I may have a solution what about double u-joints on each end?? If the problem with a u-joint is that they travel and varying speeds as they spin and it takes two at the same angle to cancel each other out, than why can't a person put two joints at each end and be done with it?? than the pinion could be set at 0 and the transmission could be at what ever angle it happens to hang down at. It is my understanding that two u-joints at each end would give you a CV joint rather than a u-joint. I was thinking a person could get 4 of the driveline flanges that bolt to the differential and have a ring machined so that two could be bolted together. Than you could have slip yoke, u-joint, H piece, u-joint, drive line, u-joint, H piece, u-joint, flange, and then the differential. I don't know if that is a really good idea or an accident weighting to happen, I simply don't know enough about drive-shafts.

on May 26, 2010, 3:34 pm, Daze wrote:

thing is, wouldn't you need two?? one at each end and if so how does that effect... the slip yoke?? as you know the OEM mustang slip yoke was designed to accommodate the differentials movement but with a Jag I believe everything was mounted solid so I wonder if the slip yoke will cause problems?? Also seams like the Jaguar driveline was attache to the underside of the car to keep it from flopping around.

on May 26, 2010, 7:12 pm, Daze wrote:

Take a look at this web page. I have not looked over all of it... but what I have looked over seams like good info. It is geared toward 4X4 applications, BUT most of it should apply directly to out situation. I am especially impressed that there is References at the bottom

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Double-Cardan-Measurements

on May 27, 2010, Daze wrote:

joe, what was your doner IRS cars year and model?? I have been trying to find info on Jaguar drivelines and non of the ones I have found have been double cardan

Last edited by Daze (10/27/2011 1:53 pm)

Reviving this thread so it can be moved to the current topics forum.

Double-cardan joints I think have rotational-speed limits, so do your calculations on what the driveshaft RPM will be at the max speed you want to be able to run.

Many cars these days use Rzeppa-type ball-and-cage CV joints in the driveshafts, BMWs typically have one at the rear for instance, the '08 GT500 shaft I've got in the shop has one BMW-type non-plunging CV at the rear and a big Porsche-axle-type plunging CV in the middle.