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BUT....I've read so many other articles and I'm getting a different math formula on how to calculate it. That link says (rearend angle)-(driveshaft angle)=(pinion angle). On another site, it says to just add them both together.
So which way is correct? Is that 2 degree difference between the rear and ds necessary?
I have a -3 rear angle, and -1 driveshaft angle. WHAT IS MY PINION ANGLE!?!?!
I'm trying to figure this out because on deceleration, it seems like my car bucks and has this tight load feeling. I'm not getting any vibrations though, so that's good. I have a MWC 9" with the adjustable short arm if that helps
1. measured the vibration damper machined surface to get the crank centerline - which carries allt he way through the trans ouput.
2. measured the bearing cap with a socket as a spacer on the yoke side of the rear U joint.
3. DID NOT MEASURE DRIVESHAFT
4. Worked to get the angles in 1 and 2 identical, and then adjusted up and down from there. At 4.2 degrees on the tailshaft and 3.7 degrees on the yoke, I call this -0.5 degrees.
This is an attempt to depict the angles that worked for me. The angles are all relative to level with the earth.
Here is an alternate configuration I've seen people use and swear by. I
could not get mine lined up like this, so I went with the prior post:
1. measure the angle at the damper as before
2. measure the angle at the yoke u-joint bearing cap as before
3. measure the driveshaft angle
4. make the interior angles match
Again, all angles are relative to level with the earth. In this arrangement, you want both interior angles of the U-joints to match - in this example, the angles at both ends of the driveshaft are 1.2 degrees.
Set the pinion to 0 deg, then check the degrees relationship to the drive shaft. Think about it this way, how many degrees do have to raise the pinion to make it run parallel with drive shaft. Ride height affects adjustments from car to car because the driveshaft height will be different in relationship to the pinion. What is your tire diameter and rim diameter?
If those angles are in collation with the center picture in the diagram provided then yes you'd have -3.5.
Yeah that's a little too much for my liking.
I actually just removed the torque arm and slightly rotated the diff housing to set the pinion at 0. I then installed the torque arm back on making sure the measurement stayed at 0. I put the driveline back on and the angle for the driveline is at 0 also. I'm going to test drive it right now to see how it feels.
Is it normal for the pinion and DS to both be at 0?
I actually just removed the torque arm and slightly rotated the diff housing to set the pinion at 0. I then installed the torque arm back on making sure the measurement stayed at 0. I put the driveline back on and the angle for the driveline is at 0 also. I'm going to test drive it right now to see how it feels.
Is it normal for the pinion and DS to both be at 0?
Are you measuring with the suspension loaded? Id leave it at zero if its a DD. I put mine at -2 since I track mine
Are you measuring with the suspension loaded? Id leave it at zero if its a DD. I put mine at -2 since I track mine
Yes it's loaded. I have the car sitting on ramps on all 4 corners, car is sitting leveled. It drove fine after the test drive and seems a bit "smoother". My car is a weekend warrior and not a DD so I'll probably add -1 to see how that does.
GM wants 1.5 degrees in a u joint working angle. If there is 0 degrees then the u joint will not roll the bearings and will lead to an early failure.
The crankshaft centerline and the pinion centerline should be the exact same angle regardless of the number. The crank at ride height should be higher off the ground than the pinion, therefore resulting in the "negative angle" at the rear joint. We generally setup most cars at 1.5-2.0 degrees depending on the application.
The crankshaft centerline and the pinion centerline should be the exact same angle regardless of the number
^^This^^
In general, when you hear people say a "Zero pinion angle" this is what they actually mean. The difference between the crank centerline angle and the rear pinion angle is zero (or pretty close to it). May not be technically correct, but is usually what is meant.
Re-read post 3 with SSVERT99's quote in mind.
FWIW, I don't even measure the driveshaft angle - I just make sure it is visibly at a slight angle at both ends. If the crank and pinion are parallel, the interior angles will match and vibrations will cancel out.
Ok I'm starting to get it a little. Sorry about all the questions and confusion.
So according to post #3, I measure the crank pulley with the angle finder (which should be same measurement as transmission output). Then measure pinion angle. Subtract the crank number from the pinion number and that will give me the pinion angle? And not measure any angle off the driveshaft right?
Pictures do help me out, so I appreciate it. I must be overthinking this too much
Ok I'm starting to get it a little. Sorry about all the questions and confusion.
So according to post #3, I measure the crank pulley with the angle finder (which should be same measurement as transmission output). Then measure pinion angle. Subtract the crank number from the pinion number and that will give me the pinion angle? And not measure any angle off the driveshaft right?
Pictures do help me out, so I appreciate it. I must be overthinking this too much
Yep, that's how I set mine up. Easiest way to think of it is the pinion should be parallel to the crank centerline. Start there, and most of your vibrations are probably gone. I still had a very slight vibration at heavy throttle, so I messed with the angles until my pinion was -0.5 relative to the crank angle, which gives me no vibrations under throttle or coasting. The driveshaft will naturally end up at a 2 degree angle on both ends, so no need to measure it.
The best place to measure the rear pinion I have found is the U-Joint bearing cap on the yoke side of the joint (get it on the bottom of rotation), using a socket as a spacer to get it level. If you have clips blocking it, then use the machined surface on the yoke, but be aware there could be a slight error. You'll still be very close in the end, though.
Don't use the housing of either the transmission or the diff. They aren't quite true with the centerlines.
OK so I have a moser 9" that I have had for awhile with a new spohn pro series torque arm that I just added. I have been having vibrations with the last torque arm (bmr long arm) or so I thought, ever since I put this set up in my car. My vibrations are on exceleration at 70+ mph, in any gear seems like. And horrible vibrations on deceleration. I did as this thread said on adjusting my pinion and I'm still having the vibrations.
I've been having some issues with the car so I decided to take the tranny out ( RPM level5 t56) even thought it shifts and drive fine. I drained the fluid and it looked metallic. So I took off the front plate and seen that there was metal shavings on the magnets in the tail shaft. So I took the tail shaft off and cleaned the **** out of the tranny with brake fluid. I reassembled the tranny because the gears and bearing looked fine from the outide lol (I never tore down the tranny all the way). The car shifts fine still but I'm thinking that it might be the cause of my vibration since none of this piece ion stuff helped. I really dont know what to do next. I know I need to send the tranny to RPM for a refreshing but it's just lot of money for something that I don't even know will fix my vibrations
05-27-2015, 01:55 AM
Pinion Angle question 
