- Thread starter
- #101
landtank said:
I deleted those because I want to re-look and answer correctly. Please stand by.....thanks!
Front DC drive shaft vibration:
- Thread starter ShottsUZJ100
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I deleted those because I want to re-look and answer correctly. Please stand by.....thanks!
- Thread starter
- #102
Here's the best pic I can do right now. I took a yard stick and carefully lined it on the front diff flange then took a pic at the T/case. The line to the T/case looks pretty close.
NOTE: I know when we measured the SLOPE of the DC shaft on it's shaft it was 9*. Had a STOCK shaft been in there it would have been LESS degrees slope because the D/C CV head is bigger and the shaft begins it's slope farther from the T/Case flange which increases the slope number. This could be why we measured we'd still needed a 2.5* correction. We might actually be really close and that D/C shaft may be the culprit?
So, my thinking is that:
We know:
T/C is 3.5* UP
FRONT PIN is 6.5* UP
Actual slope is LESS than 9* if measured via a direct line from the center of the flanges or with a standard shaft in. Let's say it's only 7.5* slope then? I'll buy an inclinomter tomorrow. How does that measure up?
NOTE: I know when we measured the SLOPE of the DC shaft on it's shaft it was 9*. Had a STOCK shaft been in there it would have been LESS degrees slope because the D/C CV head is bigger and the shaft begins it's slope farther from the T/Case flange which increases the slope number. This could be why we measured we'd still needed a 2.5* correction. We might actually be really close and that D/C shaft may be the culprit?
So, my thinking is that:
We know:
T/C is 3.5* UP
FRONT PIN is 6.5* UP
Actual slope is LESS than 9* if measured via a direct line from the center of the flanges or with a standard shaft in. Let's say it's only 7.5* slope then? I'll buy an inclinomter tomorrow. How does that measure up?
Uncle
- Thread starter
- #104
Looking at this worksheet:
http://www.pirate4x4.com/tech/billavista/PR-shaft/worksheet cv.jpg
Calculating using the slope measurement of the D/C shaft:
9 + 3.5 (TC up so you add the #) = 12.5 CV angle
(12.5* easily handled by a D/C shaft)
9 - 6.5 (pinion UP so you subtract the #) = 2.5 pinion joint angle
(Ideal pinion joint angle is 0* though that is at Cruise Throttle which can vary by 2* because the front pinion angle comes down when on the gas. Since I'm parked, my 2.5 might measure 1.5 or 0.5 at cruise throttle...pretty close)
NOTES:
"The second operating angle, the pinion op angle, should be within 0.5° (1/2)° of zero (0°) AT CRUISE THROTTLE. This is a critical point. virtually every axle (to a greater or lesser degree, depending on power and suspension) will experience some "axle wrap" or pinion rotation ( pinion rotates up in rear axle, and down in front axle) depending on acceleration and to some extent braking torque. This will of course alter the geometry of the pinion, and therefore the whole driveshaft! Since the driveshaft will presumably spend most of it's time (and therefore the effects of it's vibrations will be most annoying and damaging) in a cruise throttle condition, it is standard practice to set driveshaft geometry for this state Generally, for most cars and trucks rear axles, at cruise, the pinion will rotate up 1-2° from its static position. As such, it is common practice to shim the axle or adjust the links, rotating the pinion and changing the pinion slope at rests, such that the pinion slope is 2° lower than that required to achieve an operating angles of zero at rest. Read that bit again, carefully! It's a bit of a juggle, because as you adjust the pinion slope itself, so you also actually alter the driveshafts slope, which directly affects what your pinion angle must be, in a feedback type loop. Once you get close though, you will easily end up at the correct balance point. The point I'm making is, don't just make a whopping 20° change to the pinion angle, then weld those spring perches on and call it done. That big of a change will have effected things, so you'd have to measure and re-calc all the slopes and op angles again, as you hone in on the final setting."
Now...let's take into consideration that the true slope of a needed driveshaft for my Lexus is actually less than the 9*. That DC measured slope is falsely increased because the CV head is so large and the shaft itself begins it's slope FARTHER out from the T/C flange than the pinion flange which has a small u-joint on it. Follow me?
So, let's say the TRUE slope is 7.5*. (Nope, I'm not putting a stock shaft back in to measure this 100%) Now let's look:
7.5 + 3.5 (TC up) = 11 CV angle (good)
7.5 - 6.5 (pinion UP so you subtract the #) = 1 (Very close, BUT...add in the 1-2* for cruise throttle angle change and I could be perfect)
Shouldn't I be about perfect for the D/C shaft?
http://www.pirate4x4.com/tech/billavista/PR-shaft/worksheet cv.jpg
Calculating using the slope measurement of the D/C shaft:
9 + 3.5 (TC up so you add the #) = 12.5 CV angle
(12.5* easily handled by a D/C shaft)
9 - 6.5 (pinion UP so you subtract the #) = 2.5 pinion joint angle
(Ideal pinion joint angle is 0* though that is at Cruise Throttle which can vary by 2* because the front pinion angle comes down when on the gas. Since I'm parked, my 2.5 might measure 1.5 or 0.5 at cruise throttle...pretty close)
NOTES:
"The second operating angle, the pinion op angle, should be within 0.5° (1/2)° of zero (0°) AT CRUISE THROTTLE. This is a critical point. virtually every axle (to a greater or lesser degree, depending on power and suspension) will experience some "axle wrap" or pinion rotation ( pinion rotates up in rear axle, and down in front axle) depending on acceleration and to some extent braking torque. This will of course alter the geometry of the pinion, and therefore the whole driveshaft! Since the driveshaft will presumably spend most of it's time (and therefore the effects of it's vibrations will be most annoying and damaging) in a cruise throttle condition, it is standard practice to set driveshaft geometry for this state Generally, for most cars and trucks rear axles, at cruise, the pinion will rotate up 1-2° from its static position. As such, it is common practice to shim the axle or adjust the links, rotating the pinion and changing the pinion slope at rests, such that the pinion slope is 2° lower than that required to achieve an operating angles of zero at rest. Read that bit again, carefully! It's a bit of a juggle, because as you adjust the pinion slope itself, so you also actually alter the driveshafts slope, which directly affects what your pinion angle must be, in a feedback type loop. Once you get close though, you will easily end up at the correct balance point. The point I'm making is, don't just make a whopping 20° change to the pinion angle, then weld those spring perches on and call it done. That big of a change will have effected things, so you'd have to measure and re-calc all the slopes and op angles again, as you hone in on the final setting."
Now...let's take into consideration that the true slope of a needed driveshaft for my Lexus is actually less than the 9*. That DC measured slope is falsely increased because the CV head is so large and the shaft itself begins it's slope FARTHER out from the T/C flange than the pinion flange which has a small u-joint on it. Follow me?
So, let's say the TRUE slope is 7.5*. (Nope, I'm not putting a stock shaft back in to measure this 100%) Now let's look:
7.5 + 3.5 (TC up) = 11 CV angle (good)
7.5 - 6.5 (pinion UP so you subtract the #) = 1 (Very close, BUT...add in the 1-2* for cruise throttle angle change and I could be perfect)
Shouldn't I be about perfect for the D/C shaft?
- Thread starter
- #105
landtank said:
That's OK Rick. Thanks for your help. We'll get it figured out. Until we get a D/C shaft back that is tested as "good" we're all spinning out wheels. I've learned a lot about this topic. By the time it's smooth I'm sure I'll learn even more. I do wish I wasn't "handicapped though".
John , Rick is the guy who can really help you here... a picture is worth a thousand words
Rick - it looked to me in one of the pinion photos that also showed the tcase - that the diff was pointing slightly downward towards the ground. opposite of the tcase
Rick - it looked to me in one of the pinion photos that also showed the tcase - that the diff was pointing slightly downward towards the ground. opposite of the tcase
You're your own worst enemy here. You insist on leading and you have no clue where to go. Simple questions and requests are responded with expeditions down some tangent line of thinking with gobs of information that only vaguely relates to the question posed and further confuses the process of analysing the situation.
Whether or not you solve your vibration problem the greater lesson that needs to be learned here is when asking for help make every attempt to provide the information that person is asking for accurately and concisely.
To answer a previous question, yes I have a set of my plates available, yes I could drill them at 7* if indeed that is what you would need to correct that 2.5* error and no they are not available.
Whether or not you solve your vibration problem the greater lesson that needs to be learned here is when asking for help make every attempt to provide the information that person is asking for accurately and concisely.
To answer a previous question, yes I have a set of my plates available, yes I could drill them at 7* if indeed that is what you would need to correct that 2.5* error and no they are not available.
- Thread starter
- #108
GOT OFF THE PHONE....HAVE IT FIGURED OUT!
IF there's vibration when the DC shaft is re-installed, finding the solution is easy:
The goal is to have a matching D/S slope and front pinion angle. I am off the 2.5* like measured.
First...measure the static lift amount as is (like at my front bumper).
Second...we will slightly lower and raise the front end (via weight or jack) until the SLOPE and PINION ANGLE is 1* HIGHER (compensating for cruise throttle correction as front pinion drops down 1-2* on throttle).
Once the "corrected" height of the front end is set we will re-measure the lift height then adjust the total lift up or down accordingly with the needed pieces. (Trim packs, spacers, removal of such, etc.)
This will then set the CV slope directly at 0 degrees on throttle.
IF there's vibration when the DC shaft is re-installed, finding the solution is easy:
The goal is to have a matching D/S slope and front pinion angle. I am off the 2.5* like measured.
First...measure the static lift amount as is (like at my front bumper).
Second...we will slightly lower and raise the front end (via weight or jack) until the SLOPE and PINION ANGLE is 1* HIGHER (compensating for cruise throttle correction as front pinion drops down 1-2* on throttle).
Once the "corrected" height of the front end is set we will re-measure the lift height then adjust the total lift up or down accordingly with the needed pieces. (Trim packs, spacers, removal of such, etc.)
This will then set the CV slope directly at 0 degrees on throttle.
lets start a pool on where Shotts ends up in height using that method.
I'll take 7" of total lift.
I'll take 7" of total lift.
He is in Transmitt only mode Rick.
Romer said:
is that like running around the room with your fingers in your ears yelling "NA NA NA NA NA NA " ?
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ShottsUZJ100 said:
Correct.
ShottsUZJ100 said:First...measure the static lift amount as is (like at my front bumper).
Second...we will slightly lower and raise the front end (via weight or jack) until the SLOPE and PINION ANGLE is 1* HIGHER (compensating for cruise throttle correction as front pinion drops down 1-2* on throttle).
Once the "corrected" height of the front end is set we will re-measure the lift height then adjust the total lift up or down accordingly with the needed pieces. (Trim packs, spacers, removal of such, etc.)
This will then set the CV slope directly at 0 degrees on throttle.
That may work, but remember the arms are connected to the frame, as you lift the frame you lift the rear of the arms, rotating the pinion up.
If you only need 1.5 degrees, the first thing I would try is, loosen the 4 bushing bolts holding the arms to the axle and force the pinion down and the front of the axle up to remove the play in the bolts, tighten them and see how much improvement you get.
When I was playing with mine, I used 1/2" bolts that are threaded all the way with nuts as jacks to move the axle, the bolts go through the holes in the brackets and push on the arms. With the front bolts removed this allows you to move the axle, measure and see where it needs to be.
Mine needs a bunch!
On yours, if it dosen't need much, use a die grinder to slightly egg shape the holes in the axle bracket to allow the movement, torque the bolts and you maybe good to go?
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clarkrw3 said:
Or something!
ShottsUZJ100 said:
"Seek first to understand before being understood."
-B-
sleeoffroad
Supporting Vendor
All I can say is if you sent back the DC shaft last week, we could have had it tested and checked out by now. This is web truck building at its best.
sleeoffroad said:This is web truck building at its best.
Or perhaps it's Munchausen by Proxy.
-B-
I have a quick question. John, you say you 'can't' remove the wheel and take a pic. Are you physically incapable? If so, why are you trying to build a truck? Why not pay someone to do it right?
-Spike
-Spike
- Thread starter
- #119
-Spike- said:
Yes. If it's work-related or if it's tire changing, I'll save my arms for work and pay others to do my labor. Life sucks.
I'm not sure I understand this: "If so, why are you trying to build a truck? Why not pay someone to do it right?"
Oh...I follow you. Yep, I've been paying somebody. That's why things are taking forever. Drop off....get a ride....pick up....doesn't work....now what....crap...take back....order more parts....
Last edited:
- Thread starter
- #120
sleeoffroad said:All I can say is if you sent back the DC shaft last week, we could have had it tested and checked out by now. This is web truck building at its best.
I sent it Saturday. It was re-packed better than original.
Before ya send it back please let me know the results. Thanks!
