Cudafacthackjob with his typical drive by with the Red X and no explanation. 
driveshaft angles
- Thread starter str12-340
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Yes it is! With this Ford 9" I am building to go under Vixen for example. I did the same with it that I do with any other rear axle starting from scratch. When locating the perches, I get the location and width correct and then rotate the housing so the pinion ends up 5 degrees nose down and make my welds. Done many like that and they turn out spot on every time.
Things can change when you set you're lard *** in the seat, or mine.
I used the Tremec app on my phone, hoping they know what they are doing.
You do need to be careful (as I'm sure that most on here could figure out) not to have your phones buttons affecting your readings.
https://www.tremec.com/menu/tremec-toolbox-app/
You do need to be careful (as I'm sure that most on here could figure out) not to have your phones buttons affecting your readings.
https://www.tremec.com/menu/tremec-toolbox-app/
Big time. If you've ever seen a rear end hard launch with a go pro or some such, you can see just how much the rear axle rolls up. It's pretty dramatic. Even with a warmed up street car, it's more than you might realize.
Phreakish
Well-Known Member
I used that too and found it very important to make sure to keep the phone facing the same direction for each measurement. If your screen if facing the drivers door when measuring the engine, then it should be facing the drivers door when checking the rear. I initially just ran around the car and got measurements that were way off... but it had the angles swapped on the rear end with regard to the engine.
Phreakish
Well-Known Member
5 down relative the engine, or relative the ground? I think a lot of the confusion comes from exactly how the angle is measured.
Maybe I should have explained it a little more.
and maybe I wouldn't have gotten a red x . lol
CudaFactHackJob
Well-Known Member
What? 5-7 degrees down is INSANE for the street. That's a race car only scenario. Is that better than just a red "X"? But now I have to listen to your opinion about my opinion...
Tell us how it's done pal, instead of doing the drive by X.
If I remember right angle should be same as pinion angle. (Opposite to be more accurate.) Race typically 2°-3° Street 5°-7° This is final starting points with driver in seat. "Starting point" being the important factor. Each car is a little different. The shorter the wheelbase typically means slightly higher angle required.
No rule is ever 100%. So share any discoveries you find.
No rule is ever 100%. So share any discoveries you find.
5 down relative to the ground. This is with the rear axle on jack stands, flipped upside down.....so essentially it's 5 degrees "UP" but of course ends up 5 down since it is flipped back upright and installed.
You have to understand how it's done. Every single stock Mopar rear axle will measure between 2-5 degrees pinion down in relation to the spring perches, from the factory. When the rear axle is installed on the springs, then you measure relative to the drive shaft angle. So normally, when you set the perches with the pinion 5 degrees down relative to the GROUND, it ends up about perfect when installed, since normally, the drive shaft angle from the transmission is between 2-5 degrees, depending. Then if you need to fine tune (I rarely have had to) you can use pinion shims under the perches. Geeze yall, this is grammar school geometry. It's not difficult.
For those that might not know, Just remember to get shims with centering holes the same diameter as the leafspring bolt, not ones with too big of a hole.(cheap shims typically have big centering holes) You need to remove the leafspring bolt and bolt down the shim as part of the leaf spring pack. Depending on shim size you may need longer bolts. And use a C clamp to keep the leaves compressed when removing the bolt.
I dunno, A body has the perches level and the pinion pointing up 5*.
If the trans output is at 0*, regardless of position with the ground, the pinion should be in the 2-4* down position to account for roll up under cruise.
Anymore than 4* usually starts to strain the U-joints
JMO and this
If the trans output is at 0*, regardless of position with the ground, the pinion should be in the 2-4* down position to account for roll up under cruise.
Anymore than 4* usually starts to strain the U-joints
JMO and this
I couldn't have written it any better. 
mopowers
Well-Known Member
That's how I've always done it. Make the pinon parallel with the trans/engine centerline and rotated it down 2-4*. Easy peezy.
Why even include the driveshaft in the equation?
Has anyone ever attempted a harmonic type balancer for a driveshaft? This of course wouldn't replace having a balanced shaft. But a balanced shaft is still static. It certainly doesn't take into account thermo, or lateral stresses. Would probably be more effective for high speed applications.
Remember. There are no dumb ideas. Just dumb people posting them!
Remember. There are no dumb ideas. Just dumb people posting them!
Ford used balancers like that on drive shafts for decades.
I know they were big on split driveshafts. Never seen a balancer on a single shaft. (But that just demonstrates my lack of on hands experience with Fords.)
I'm sure it's been thought and tried. Everything has these days. Lol.
Phreakish
Well-Known Member
All my driveshaft have been dynamic balanced. Second order vibrations can be a killer.
A truly vibration free shaft would simply use CV joints at both ends, or those rubber donuts the eurocars love so much. Not sure either is a good idea for but power cars with traction..
A truly vibration free shaft would simply use CV joints at both ends, or those rubber donuts the eurocars love so much. Not sure either is a good idea for but power cars with traction..
Just to be clear what my situation is. The car is on a 2 post lift that is adjusted so that the flat bottom of the rocker panels is flat (0 degrees). The back of the car is supported on tall jack stands under the rear housing tubes so that all the weight of the back of the car is on the springs. When in this position, the trans is also at 0 degrees and for reasons that are too involved to go into here it would be difficult to change. In this position the pinion angle is 3 degrees down. The driveshaft is 5 degrees down from the trans to the rear end. This means that overall the pinion is 3 degrees out of parallel with the trans. Therefore the angle between the trans and the driveshaft is 5 degrees down and at the pinion and driveshaft it is 8 degrees up.
After reading all these posts and looking at the diagrams and going to links to video explanations of how this should work, it seems that what should happen is to shim the pinion up 3 degrees so that the driveshaft angles are approximately 2 degrees up and 2 degrees down and the transmission shaft and the pinion are parallel. I throw this out there hoping to get some specific input on WHY this ISN'T what I want to do.
The only thing that I haven't been able to factor in is how much the pinion angle would change driving on a flat road at 60 mph. If it matters the leaf springs are new 6 leaf ESPO springs.
Unrelated to my situation, does anybody know what the angle of the original transmission is on one of these cars from the factory? I'm trying to figure out what people are saying regarding the pinion angle from the factory and how this translates to all the driveline angles from the factory.
Thanks for all the input
After reading all these posts and looking at the diagrams and going to links to video explanations of how this should work, it seems that what should happen is to shim the pinion up 3 degrees so that the driveshaft angles are approximately 2 degrees up and 2 degrees down and the transmission shaft and the pinion are parallel. I throw this out there hoping to get some specific input on WHY this ISN'T what I want to do.
The only thing that I haven't been able to factor in is how much the pinion angle would change driving on a flat road at 60 mph. If it matters the leaf springs are new 6 leaf ESPO springs.
Unrelated to my situation, does anybody know what the angle of the original transmission is on one of these cars from the factory? I'm trying to figure out what people are saying regarding the pinion angle from the factory and how this translates to all the driveline angles from the factory.
Thanks for all the input
Phreakish
Well-Known Member
At cruise power, you'll roll the axle up 3-5 degrees more, usually. That's why the comment is usually to start 3 degrees "down"
The problem with trying to use OEM angles, is that once the driveshaft has changed length or the location of the output has moved, it's all moot.
Engine should usually be about 2 degrees nose up (damper higher than trans output). Actual angle varies though depending on trans mount, engine mounts etc. We all shim out junk to make headers fit or because of aftermarket parts, etc.
I HAVE explained it. More than once. You set it like you want. I hope it doesn't vibrate. Good luck.
CudaFactHackJob
Well-Known Member
What is this "grammar" school you speak of? Inquiring millennial minds want to know...Please use "gee, I'm a tree" in a sentence.
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