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Pinion Angle Question

Need some seasoned expertise.

I have the DSE sub and quadra link rear. LS7, DSE motor mounts, ATS T-56 crossmember.

My Trans tail shaft is 4 degrees down and my pinion on the 9 inch is 2 degrees up.
I used a craftsmen magnetic protractor to check the angles.

DSE told me to set my rearend at 2 degrees DOWN. DOES THIS MAKE SENSE TO anyone? Isn't this a cumulative difference of 6 when 3 or less is desired?

Thanks in advance.

Jim,

I don't have the answer but I saw a discussion a while back and they were using this link. Perhaps it may help http://www.vibratesoftware.com/html_...aft_Angles.htm

It is very confusing. Basically you need to try and get your driveshaft to driveline and pinion angle within .5 degrees working angle if you can. .5-3.5 is the general specs. You need to measure you angles off your u joints with a socket and angle gauge. The lower you car gets the more difficult this becomes if you are using stock components.
For instance I am running DSE half height bushings, g bar, DSE sub, and at ride height my driveshaft is pointing down towards the rear .3 degrees. The driveline angle is 4.5 down leaving me a front u joint working angle of 4.2 degrees which is out of spec. To get to that measurment I have to run 3 degrees on downward pinion angle. So 3 degrees plus a driveshaft angle up of .3 degrees gives me 3.3. I will have to cut my tunnel to get the specs I want. The bottom line is will it vibrate? Not sure yet....if it does the tunnel will be cut.

Quote:

Phasing is a term that describes the alignment of the single-cardan joints on opposite ends of the drive shaft. As discussed above, a single-cardan (or u-) joint does not rotate at a constant velocity if the operating angle is non-zero. The drive shaft speeds up and slows down slightly as it rotates due to the nature of the joint. One way to reduce this is to make sure the joints at each end of the drive shaft are aligned properly. If the yokes on each end of the shaft line up with each other, as seen in the figure below:

http://www.drivelinespecialist.com/t...oint_angle.gif

Quote:

If the shaft is ever taken apart, it is important to get it re-aligned properly when it is re-assembled. One way to do this is to mark both sides of the slip yoke. However, you should check that the joints really do align properly, don't assume they are. The reason for the phasing is that the speed variation of the joint is related to its operating angle and its angle of rotation. In order to get the most effective cancellation, the joint yokes *must* be aligned exactly with each other and the operating angles must be identical. Any variation in either angle will show up as un-cancelled vibration, which will get worse at higher speeds

dse wants you to weld brackets on rear end plumb, when pinion is pointing 2 degree's down, that way you got alittle bit built in so you can keep as many threads engaged in the rod ends as possible

From what I have read, and discussed, there are two main points of view on driveline angles besides the specs and math. And that is should the angles be measured and set STATIC or adjust for DYNAMIC conditions. I have discussed this with Kyle at DSE and I believe his point of veiw is on the side of dynamic adjustment or setting. Static being as the vehicle is setting at ride height without any load. I call this the street rod setting because it looks good sitting still. The Dynamic setting would take into count the type of suspension, bushing, and horse power. The pinion angle is going to climb as the vehicle is loaded. The more load, the softer bushing, or at the extreme leaf springs, the more it will climb. My ChevyII has a "Mule" four bar knock off which is an early version of DSE's swivel link four(five) bar set up and Kyle advised 1 degree neg or down stateing that it would rise under dynamic conditions.

Thanks for the website info. That explains a lot.

My terminology was wrong. I never knew that the trans tail shaft / yoke pointing down below the horizon was actually an up angle.

I set my pinion (by adjusting the swivel arms) to 2 degrees up. I was trying to emulate the "hot rod" style of parallel planes between the trans tail shaft and the pinion with working angles less than 3 on the driveshaft.

According to the website above my set up isn't acceptable as the difference between my working angles is 2 degrees. The website states that .5 is acceptable.
I am going to set my pinon angle back to the starting point of 2 down.

well just in case someones reading this and missing the point, your 2 deg down needs to be from a properly aligned static setup. meaning if your pinion points 5 up, bring it down to 3. if its 2 down, take it down 2 more. you cant just set it at 2 degs down from whatever (level, the frame, the driveway) and call it good.

the 2 degs down allows for the pinion wrap up and will then make your dynamic specs the same as your static specs.

Tim