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Premium Member
02 DubCab 4x4
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Discussion Starter #1 (Edited)
Low Speed Driveline Shudder.....now with VIDEO

Here are some sites that i have felt useful for my education in driveline dynamics.


by the way, we have a CV drive shaft.

http://www.4x4wire.com/toyota/tech/driveline/


and if anyone is wanting to increase the angle of their driveshaft joints

http://www.4x4wire.com/toyota/tech/cvmod/


other vibration issues and solutions
http://townhall-talk.edmunds.com/direct/view/.ef25c2b/6752
http://townhall-talk.edmunds.com/[email protected]@.ef25c2b/6994#6994

http://expeditionportal.com/forum/showthread.php?p=2572


http://www.4xshaft.com/index.html Tom Woods custom driveshafts.


I bet all of this is an out of line driveshaft issue..... I'm gonna check mine tomorrow with what tools I have. I'd be willing to bet that our vibration issues are related to how hard we cranked out rear axles in getting our AAL's under our leaf springs. Those that were more experienced and gentle with their rear ends came out with no or less vibration. I myself was pretty rough with mine. I'd bet i'm just out of alignment and my two joints are running elliptical dances under acceleration. Is anyone out there with me on this?
 

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Mine is better than yours
'06 Dbl-Cab 4x4 Taco
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1,211 Posts
Before I seperated my rear leafs or even loosened the u-bolts I took a straight edge and drew a line from the main leaf vertically to the spring perch with a silver sharpie. That way I was able to line everything back up exactly as it was before I took it apart. I did this with both my '05 and '06 and neither had any vibrations at all.

I went a step further with the '06 when adding the AAL. Everyone that did this themselves I'm sure you saw the thin metal plates between every leaf, keeping the leaves from touching each other. When everyone added the AAL, you now have 2 of the leaves touching each other which may be causing alot of everybodys squeaking rear ends.

When I re-assembled my leaf packs, I made an additional galvanized plate so that none of the leaves were touching each other at the center bolt just like the factory, so no squeaks.

Marc M
 

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Registered
'06 Prerunner TRD
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1,093 Posts
interesting... maybe a one piece drive shaft is the only way to go... I hope not though! DAMN!
 

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Humble Servant
2012 DC PreRun Auto
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1,158 Posts
eyedoc said:
Here are some sites that i have felt useful for my education in driveline dynamics.

by the way, we have a CV drive shaft.

http://www.4x4wire.com/toyota/tech/driveline/


...

His explanation isn't technically precise, but the resulting conclusion is correct.
(The "path" of the U joint doesn't change to an ellipse, but a polar plot of the angular velocity vs. angular position would be elliptical.) To envision what really happens, keep in mind that, for a shaft rotating at constant angular velocity (rpm), a point on the shaft (including the U joint) at a given radius from centreline will remain at the same speed. However, if you move to shorter radius from centreline, the tangential speed of the point is less, and the inverse is true. For the yoke attached to the transmission with a constant speed output, the journal bearings are at a fixed radius from the centreline of rotation, and therefore are at a constant tangential speed. If you displace (pivot) a U joint between the tranny and drive shaft at say, 3 degrees, then the journal brgs in the yoke of the drive shaft will be at the same radius as those on the tranny yoke only when they are 90 degrees to the bend (in most cases, we're talking the 3 and 6 o'clock positions). Here they have the same tangential speed as the journal brgs of the tranny yoke, and the driveshaft, as you would expect, is rotating at the same rpm as the tranny output. But when the shaft rotates 90 degrees, they are at a shorter radius from the centreline of rotation of the tranny output (R x cos 3degrees), and therefore, the tangential velocity of the driveshaft journal brgs is less than those of the tranny. (though only about 0.14% less) But since the driveshaft journal brgs are at a fixed radius from centreline of the driveshaft their tangential speed is proportional to the driveshaft angular velocity (rpm). This means that the driveshaft (at this position of the Ujoint) is spinning at a lower angular velocity than the tranny output (specifically, 99.86% of the tranny output). When the shaft rotates another 90 degrees, the yoke of the driveshaft will again be aligned perpendicular to the pivot angle, and the driveshaft will again be at the same angular velocity as the tranny output. As a result, the driveshaft is constantly slowing down and speeding up relative to the tranny output. If this was conveyed directly to the wheels, it would be very noticeable, and really hard on tires and the mechanical components. But the U-joint at the opposite end is aligned for the exact negative of the angle at the tranny end (the first at +3 deg, the 2nd at -3 deg). Similar to the connection between the tranny and driveshaft, the driveshaft vs. differential input will have the peculiar behaviour of the displaced Ujoint, but the exact negative. (again, the displacement causes the driveshaft yoke brgs to be at the same radius as those of the pinion's yoke (measured from the pinion centreline) when 90 deg to plane of the 3 deg bend, and at a smaller radius when in the same plane as the bend. So as the upper Ujoint causes the drive shaft to slow to 99.86% of the tranny output RPM, the lower Ujoint causes the pinion yoke to speed up to 100.14% of the driveshaft rpm. The result is that the differential's input pinion is spinning at virtually the same rpm as the tranny output, while the driveshaft is slowing and speeding up with every 90 degrees of rotation.

The mass of the driveshaft will cause some vibration, but generally this isn't sufficient to cause problems as long as the angle of the Ujoints is not severe. (larger angles will cause wider variation in angular velocity and a larger vibrational output)

The above is why the yokes must be in phase, the angles at the tranny and the diffential kept equal, and the angles not allowed to get too large.


As for a CV joint, I really think my PreRunner DC has Ujoints, not CVs, Although it wouldn't surprise me to learn that the 4x4s may be equipped with CV joints, either in the front drive shaft or in both.

[CV joints, or Constant Velocity joints, are designed to connect the drive shaft with virtually the same angular velocity as the input. They are significantly more expensive and generally a little more susceptible to contamination. They are almost a given on front drive vehicles as Ujoints to two separate driveshafts are difficult to manage given the changes in angles and velocities of the two wheels.]
 

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Premium Member
02 DubCab 4x4
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3,009 Posts
Discussion Starter #6
Ok guys....

I went outside and jacked my truck up and placed the frame on stands. then i jackedup the pumpkin so that the tires were well off of the ground. then, CAREFULLY, I started the truck and put the thing in drive and made sure that the truck still had the low speed vibration by taking it up to a little over 2,000 rpm's or around 30mph.....I was a little scared, but pushed forth. I noticed the vibration and where it happened in the RPM range. then i kept her in drive at idle and got under the truck CAREFULLY and ready to lurch out of there if something unforseen happened....I HAVE VIDEO THAT I'LL POST IN A MINUTE. what i saw under there was that my driveline behind the carrier was not centered and was off center while turning (thus the vibration) and in front of the carrier was perfectly turning. From just looking at the thing while it was turning and my BFG's were turning a few inches from my head, i came to the conclusion that the thing was in a bind. so, i turned the truck off and crawled back under there and loosened the 14mm bolts on either side of the driveline and what did i see??? the whole driveline shifted anterior-posterior and relieved undue stress from the system. I then tightened the two bolts back, torqued them, started the truck and suddenly it felt more smooth through the acceleration back up to 2,000 rpm.....as excited as i was to take the truck on a test drive, i crawled back under the truck and took another video to show how the driveline turn had improved and NO MORE visible stress in the system and she was turning beautifully....I"LL POST IT IN A MINUTE AS WELL. I then took her on a drive and i must say that I noticed a huge improvement. there is still a slight shudder, but nothing like it was. I'm going to measure the pinion angle sometime soon and see if i can install the 2.5 degree shims. So far, i have NO carrier bearing drop and NO shims....... ONLY the toytec 3" lift with 885 coils, OME front shocks and AAL's in the rear with stock TRD shocks....

please, do not try this at home...........THIS IS VERY DANGEROUS and could be life threatening!!!!
 

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Premium Member
02 DubCab 4x4
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3,009 Posts
Discussion Starter #7


notice just after the carrier at the shaft how it is rotating "out of center" on each rotation.







This one is just as it was getting dark outside, i tried to illuminate with my halogen hand light.... but trust me, it turns much more smoothly.





Here is a picture of the carrier as it was before I let the stress out of the system.







And, a photo of the driveshaft now, in line as I EYEball it.






And, here is my pinion angle before the adjustment.

 

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Premium Member
02 DubCab 4x4
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3,009 Posts
Discussion Starter #8
Pumpkin before the adjustment to the carrier... my head was seriously feeling some wind from the rear drivers side tire spinning within inches from my "pumpkin"...whew!





Pumpkin after the carrier adjustment....no real change as i saw it.

 

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Trevor
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2,026 Posts
Ok first, very nicely done on the write-up and vids.:thumbup:
Secondly though, you're nuts! To be crawling around under your truck with your truck on jack stands and the wheels spinning that fast. That's a news headline just waiting to happen.:eek:
 

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02 DubCab 4x4
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3,009 Posts
Discussion Starter #10
Adventure North said:
Ok first, very nicely done on the write-up and vids.:thumbup:
Secondly though, you're nuts! To be crawling around under your truck with your truck on jack stands and the wheels spinning that fast. That's a news headline just waiting to happen.:eek:

Trust me, i know.... I ran it a couple of times through the rpm's to make sure it was stable. I checked and double checked the jack stands and lift under the rear end......AND I used the zoom on my camera so i wasn't so close as the video seems. I also knew it might help other TN members to have video to reference in the future.
 

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i give you credit for having the balls to stick your head infront of a moving tire while the truck is on a low capacity jack.
 

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'06 Prerunner TRD
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holy crap! you have some serious stones man! you may just be the dumbest smart guy I know! actually, that was a great idea... glad you didn't get hurt... and I will be doing this adjustment tomorrow!
 

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'06 Prerunner TRD
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Just did this myself and started from a stop about a dozen times and couldn't feel ANY shudder at all any more! AND it's kind of chilly outside, which usually makes my shuddern worse! HAHAHAHA I am so happy right now!!!!!!!!!!!!!!!!!!!

eyedoc- I owe you lunch and some beer man because you just saved me a couplle hundred bucks on a one piece drive shaft!
 

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02 DubCab 4x4
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Discussion Starter #14
pointerDixie214 said:
Just did this myself and started from a stop about a dozen times and couldn't feel ANY shudder at all any more! AND it's kind of chilly outside, which usually makes my shuddern worse! HAHAHAHA I am so happy right now!!!!!!!!!!!!!!!!!!!

eyedoc- I owe you lunch and some beer man because you just saved me a couplle hundred bucks on a one piece drive shaft!

Awesome..... glad I could help! This may end up biting me in the A** from those more experienced than I......... but, sometimes the most complex problem has the most simple of solutions. There is a Law or Principle named after it....can't remember it right now.....Hmmm
 

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Theatre Nerd Person...yea
Tacoma
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eyedoc said:
Awesome..... glad I could help! This may end up biting me in the A** from those more experienced than I......... but, sometimes the most complex problem has the most simple of solutions. There is a Law or Principle named after it....can't remember it right now.....Hmmm
Would it be KISS? KISS = Keep It Simple Stupid
 

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Humble Servant
2012 DC PreRun Auto
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1,158 Posts
Right on.

That's the fundamental rule of forensics as well- look for the simplest/easiest/cheapest first. (Well, actually, in forensics, the cardinal rule is to do the least destructive testing first, but, given you weren't planning to cut your truck into little pieces -yet...)

If I understand your notes correctly, the carrier bracket was either off center or off-angle from alignment btwn the output and the differential's pinion input. In addition to putting the system in a physical bind, it would likely put the two U-joints in a position where the angles didn't cancel, and the alternating portion of the driveline would be additive instead of cancelling at the last Ujoint.

Congrats.

OH, and yes, you are a little crazy. But thanks for sharing.
 

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'06 Prerunner TRD
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the Pricipal or law you are talking about is Ocham's Razor... where the simplest solution is most likely the correct one... and thanks again!
 

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02 DubCab 4x4
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Discussion Starter #18
pointerDixie214 said:
the Pricipal or law you are talking about is Ocham's Razor... where the simplest solution is most likely the correct one... and thanks again!

There ya go!!! that was on the movie "Contact" right?
 

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well, latest news... I still have a minor shudder after this. However, it is MUCH less noticible (I can only tell every now and then) and I did this last night in the dark so today with some daylight I will do it where I can see to line up the angles... I am pretty sure it will work...
 

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02 DubCab 4x4
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Discussion Starter #20
pointerDixie214 said:
well, latest news... I still have a minor shudder after this. However, it is MUCH less noticible (I can only tell every now and then) and I did this last night in the dark so today with some daylight I will do it where I can see to line up the angles... I am pretty sure it will work...
Yea, same here.... I have to REALLY feel for it. I'm wearing my brakes out starting and stopping and accelerating to feel the darn thing....I'M HAPPY NONETHELESS... I don't have to buy a one piece driveshaft any longer.

I do want to find some way of lining up my driveshaft though in a lateral way so that it shoots straight back to the punkin'. And I want to do more than "eyeball" my pinion angle to see what it is, remembering to keep it around 1 degree under.
 
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