Pinion Angle Help
11-17-2011, 12:44 AM
#1
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Pinion Angle Help
Ok long story short, I installed a shaftmaster DS a few months back and have yet to find the proper PA adjustment. After changing it from 1-3 degrees and still having vibrations I am starting to wonder if I am reading the gauge wrong.
I have two gauges, an analog one and a digital one. The first reading from the transmission bell housing base has been zero'd out to read OO. The analog gauge is reading O as well. The car is on ramps and is NOT level.
Now the the reading on the pinion flange with the digital gauge is \/ arrow down 1.0 .... Analog gauge "to the right" 1.5
My confusion is: "is this a negative reading or a positive one?" I feel like an idiot here but everybody I have asked isn't sure either. This setting is slightly longer than the stock piece. I placed it up there and compared.
I have tried 1-3 degrees with arrow pointing ^up and all settings had vibration. So I started doubting my assumptions and had to ask. Most people shorten the UCA to get the proper PA. Thats not working for me as every setting with it shorter produced vibration on decel.
So in the pics is it negative or positive?
I have two gauges, an analog one and a digital one. The first reading from the transmission bell housing base has been zero'd out to read OO. The analog gauge is reading O as well. The car is on ramps and is NOT level.
Now the the reading on the pinion flange with the digital gauge is \/ arrow down 1.0 .... Analog gauge "to the right" 1.5
My confusion is: "is this a negative reading or a positive one?" I feel like an idiot here but everybody I have asked isn't sure either. This setting is slightly longer than the stock piece. I placed it up there and compared.
I have tried 1-3 degrees with arrow pointing ^up and all settings had vibration. So I started doubting my assumptions and had to ask. Most people shorten the UCA to get the proper PA. Thats not working for me as every setting with it shorter produced vibration on decel.
So in the pics is it negative or positive?
11-17-2011, 01:08 AM
#2
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Join Date: Sep 2011
Posts: 1,226
I believe the way the analog one is pointing, assuming you want it to be at 0 too <not sure never done this>
the left side of it needs to go up.
But thats just my forum-warrior guess. Hopefully we have a smart person answer behind me
the left side of it needs to go up.
But thats just my forum-warrior guess. Hopefully we have a smart person answer behind me
11-17-2011, 01:14 AM
#3
I think you are reading the wrong place. Is that the vibration dampener you put the digital level on?
Take a reading on the diff cover surface. Try to place it so that you read the machined back surface of the differential housing.
Then take a reading on the oil pan rail or some other part of the engine that is parralel to the crankshaft. Don't trust the trans pan, though it may be OK. You could use the back face of the block or front face of the trans bell, if either is halfway accessible.
Now about reading the numbers...
If you read a horizontal surface and then a vertical surface, you may have to factor in 90* so don't worry about the number. Your dial face level is the easiest to use. Viewing from the same side of the car, you would expect the needle to be behind the 90* vertical. 3 degrees is a myth, if your crankshaft is at anything else. You want the pinion to match the crankshaft. Make sure you have a full tank of gas and the car is sitting at ride attitude, not jacked up in the rear. You want full weight on the rear suspension. It is also a good idea to put the driver (and passengers?) in the seats.
Take a reading on the diff cover surface. Try to place it so that you read the machined back surface of the differential housing.
Then take a reading on the oil pan rail or some other part of the engine that is parralel to the crankshaft. Don't trust the trans pan, though it may be OK. You could use the back face of the block or front face of the trans bell, if either is halfway accessible.
Now about reading the numbers...
If you read a horizontal surface and then a vertical surface, you may have to factor in 90* so don't worry about the number. Your dial face level is the easiest to use. Viewing from the same side of the car, you would expect the needle to be behind the 90* vertical. 3 degrees is a myth, if your crankshaft is at anything else. You want the pinion to match the crankshaft. Make sure you have a full tank of gas and the car is sitting at ride attitude, not jacked up in the rear. You want full weight on the rear suspension. It is also a good idea to put the driver (and passengers?) in the seats.
11-17-2011, 11:23 AM
#4
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11-17-2011, 12:19 PM
#5
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Join Date: Dec 2009
Location: TN
Posts: 671
From everything I've seen, you should read a zero on your pinion flange and a -2 on the driveshaft when it's properly adjusted under a full load with jack stands on the axles and front wheels on ramps distributing the load evenly. Thats pretty standard I think. Hate to see your having problems with that shaft because I haven't had any trouble out of mine. I'm using rear Roush springs that are a 3/4" drop as well.
The mechanical gauge in the pic is showing negative. It's confusing with the red window at the bottom but since it reads to the right of zero with the red window on the bottom of the gauge its negative. If the gauges red window was at the top towards the driveshaft it would read to the left of zero which is negative. Get it? I can't tell if it's negative one or two however but your close.
Thing is...I highly doubt being off a degree or so is giving you the wild vibrations your having.
The mechanical gauge in the pic is showing negative. It's confusing with the red window at the bottom but since it reads to the right of zero with the red window on the bottom of the gauge its negative. If the gauges red window was at the top towards the driveshaft it would read to the left of zero which is negative. Get it? I can't tell if it's negative one or two however but your close.
Thing is...I highly doubt being off a degree or so is giving you the wild vibrations your having.
11-17-2011, 01:04 PM
#6
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Join Date: Mar 2008
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Posts: 153
It's more confusing to make sense of what you've done than it is for me to explain an alternative method of measuring...
Both working angles should be .5-3 degrees and within 1 degree of one another.
Angles sloping in the same direction should have the smaller reading subtracted by the larger reading. Angles sloping in opposite directions should be added together.
Measure the tailshaft angle by turning the output shaft flange so that a ujoint cap is parallel to the ground. Remove the clip and place your angle gauge on the cap. Note the position of the needle relative to "0". This is your first angle reading.
Turn the shaft 90* so that the shaft ujoint cap is now parallel to the ground. Remove the clip and place your angle gauge on the cap. Note the position of the needle relative to "0". This is your second angle reading for output angle. Based on my previous comments about slope angles, either add or subtract to calculate your first WORKING ANGLE. Again, this should be at least .5* to allow the caps to rotate and evenly wear the needle bearings but no more than 3* to prevent binding in the joint.
Perform the same procedure at your pinion angle, measuring the slope of the pinion and of the shaft adding or subtracting to calculate the WORKING ANGLE. Not only should this angle be .5-3* but it should also be no more than 1* greater than or less than the other working angle.
Of course, make sure the entire weight of the vehicle both front and rear is on the suspension and on level ground. Simply putting ramps under the drive wheels will not accomodate the driveline angles properly.
Ideally, this procedure is performed on a drive-on hoist.....
Also, make sure the shaft is not bent and doesn't runout. Imbalance may also be your issue (regardless of how nice the shaft is, sometimes things just aren't balanced properly). A bent or imbalanced shaft will give you a 1st order vibration (1 irregularity per shaft revolution).
Make sure the ujoint flanges are perfectly line up as well. Incorrect phasing (twisted shaft) will create the same 2nd order vibration (2 irregularities per shaft revolution) that incorrect driveline angles will give.
If your working angles are .5-3* and within 1* of each other, the shaft does not appear to runout and the flanges are phased properly - you likely just have an imbalanced shaft.
If you find the right shop, they will have a tool from a company called Vitronix (MTS4000) that can measure the vibration to determine if it's 1st or 2nd order and thus eliminate possible causes. This tool can also be used to balance a driveshaft using two hose clamps (or pinon flange weights). This option is much better than having the shaft balanced individually because when the shaft is balanced on the vehicle (as the MTS4000 does), the entire rotating assembly is matched to the shaft. In essence, you balance the output shaft, drive shaft, pinion flange and pinion shaft.
Both working angles should be .5-3 degrees and within 1 degree of one another.
Angles sloping in the same direction should have the smaller reading subtracted by the larger reading. Angles sloping in opposite directions should be added together.
Measure the tailshaft angle by turning the output shaft flange so that a ujoint cap is parallel to the ground. Remove the clip and place your angle gauge on the cap. Note the position of the needle relative to "0". This is your first angle reading.
Turn the shaft 90* so that the shaft ujoint cap is now parallel to the ground. Remove the clip and place your angle gauge on the cap. Note the position of the needle relative to "0". This is your second angle reading for output angle. Based on my previous comments about slope angles, either add or subtract to calculate your first WORKING ANGLE. Again, this should be at least .5* to allow the caps to rotate and evenly wear the needle bearings but no more than 3* to prevent binding in the joint.
Perform the same procedure at your pinion angle, measuring the slope of the pinion and of the shaft adding or subtracting to calculate the WORKING ANGLE. Not only should this angle be .5-3* but it should also be no more than 1* greater than or less than the other working angle.
Of course, make sure the entire weight of the vehicle both front and rear is on the suspension and on level ground. Simply putting ramps under the drive wheels will not accomodate the driveline angles properly.
Ideally, this procedure is performed on a drive-on hoist.....
Also, make sure the shaft is not bent and doesn't runout. Imbalance may also be your issue (regardless of how nice the shaft is, sometimes things just aren't balanced properly). A bent or imbalanced shaft will give you a 1st order vibration (1 irregularity per shaft revolution).
Make sure the ujoint flanges are perfectly line up as well. Incorrect phasing (twisted shaft) will create the same 2nd order vibration (2 irregularities per shaft revolution) that incorrect driveline angles will give.
If your working angles are .5-3* and within 1* of each other, the shaft does not appear to runout and the flanges are phased properly - you likely just have an imbalanced shaft.
If you find the right shop, they will have a tool from a company called Vitronix (MTS4000) that can measure the vibration to determine if it's 1st or 2nd order and thus eliminate possible causes. This tool can also be used to balance a driveshaft using two hose clamps (or pinon flange weights). This option is much better than having the shaft balanced individually because when the shaft is balanced on the vehicle (as the MTS4000 does), the entire rotating assembly is matched to the shaft. In essence, you balance the output shaft, drive shaft, pinion flange and pinion shaft.
Last edited by 1990lxhatch; 11-17-2011 at 01:12 PM.
11-18-2011, 01:23 AM
#7
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I appreciate all the input guys. Timmbo, I originally had a setting where the uca was little shorter than this, it gave no vibes but did have a lot of noise over 95 mph. Me wanting perfection started to mess with it and kept making it shorter which always gave me vibrations. Now I am going the other way and making it longer. This is slightly longer than a stock uca. Whether the gauge is reading + or - is what's been confusing. So for now I'm saying forget the #, let's find the right position of the uca.
I have had my car on ramps all week. It's down, the angle is set and I have races to run Friday and Saturday night. It the sob vibrates too much after my first qualifying run I'll just jack the bitch up and give it some turns. Its not the space shuttle, it's a mustang muthafukka! Lol
I have had my car on ramps all week. It's down, the angle is set and I have races to run Friday and Saturday night. It the sob vibrates too much after my first qualifying run I'll just jack the bitch up and give it some turns. Its not the space shuttle, it's a mustang muthafukka! Lol
11-19-2011, 01:42 PM
#10
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Took it to the track Friday night. I felt vibrations on the way there so I got under there and made an adjustment to the uca before my first race. Then after the next three runs I made more. The up side is I have done this so much, even with working around the hot exhaust pipes and differential I can get in done in less than 10 minutes. LOL The downside, I'm not sure I will ever find a sweet spot. If it was giving me better times I could see the advantage, but my times have not improved.
Even with all the vibration BS I still had a great time and even qualified #1 with a near perfect light .501, (perfect being .500) but then lost two rounds later with a .496 light.
NHRA Napa driver Ron Caps is coming tonite to sign some autographs and is gonna race somebody. Too bad he is a dodge guy or I would offer to let him run my car.
Even with all the vibration BS I still had a great time and even qualified #1 with a near perfect light .501, (perfect being .500) but then lost two rounds later with a .496 light.
NHRA Napa driver Ron Caps is coming tonite to sign some autographs and is gonna race somebody. Too bad he is a dodge guy or I would offer to let him run my car.