Checking Driveling Vibration & Calculating It.
 

First Off
RPM and Drive-line Vibrations - Looking at the Gearing and Engine RPM's

Seeking to Figure - Drive Line - RPM to see If the Drive Shaft may be
an Issue as it is Past it's Design .. Limit ..

I see where a few stated 45 - 48 Mph & 1 or 2 say Run up to 55 Mph
Pumpkin Gear 5:14

1954 4 Speed - with PTO - Type of Transmission .

V8 Spinning 4000 RPM with 5:14's in Third Gear or 4th Gear
Approx what RPM is Drive-Shaft Spinning ?

Re: Checking Driveling Vibration & Calculating It.
 

top gear is 1:1, so the driveshaft speed will be the engine rpm.

if you need a gearing calculator to figure out what the effect the rear axle ratio and tire size will have on engine rpm, I like to use the unix nerd one I found years ago for BMW, easy to change, you might have to do an inch to mm conversion on your tire size if its different than the width in mm/aspect ratio/rim diameter standard though.

enter your tire diameter, enter rear gear ratio, enter rpm and use 4th gear, its 1:1, then select calculate speed. or, if you know speed, enter speed and calculate rpm.

http://www.unixnerd.demon.co.uk/revs.html

working backwards (entering speed and calculating rpm), you can see what the effect of a lower gear ratio will be.

Re: Checking Driveling Vibration & Calculating It.
 

Thank You
Yes those Calu. are Handy :

2.5 Inch Drive Shaft - 54 inches long - Has a Max Safe Limit of 3148 RPM
with 1/2 Critical Vibration Drive-Line being - 2802 Rpm - They are Referring to Harmonic's @ 2802 RPM . .

It Calu. to Potential Speed of 52.0 - 55.0 Mph - depending on Tires Size .
Cruising Speed : 40 Mph - 46.4 Mph - all these being in Safe RPM Ranges .

Now the Other Vibration Drive-Line - Item .. ( It Seems everyone Here on this Site has talked about these Angles )
But No Where did I find anything about the Designed Offset - built into the Rear Gear and Or the Transmission .

Many 4 Speeds with PTO or With Out - look to be - Off Center approx 2 " Out Put Shaft ; and the Rear Gear just looking approx 4 " at Pinion . .
with a Carrier in between . . ( Will Measure Soon ) - these Offsets have a Direct Impact on Drive Line Angles . .

[IMG]http://i1263.photobucket.com/albums/...psmmm7cvlw.jpg[/IMG]

Re: Checking Driveling Vibration & Calculating It.
 

The offset in the plan view can be disregarded because they are equal and opposite; they cancel each other out .

Re: Checking Driveling Vibration & Calculating It.
 

OK - Keith I think I understand the Canceling out Point - in 1 Plane
as We look at it ( Side View ) - how about ( Top View ) or as I always say
The Other Plane `\ : - )

That's the Trans Offset & Pinion Off Set - I'm concerned with ?

So Both the Out Put Shaft on Trans Tail and Input on Pinion - would
need to be Same Dim. Off - ( Center Line of Chassis )
Hence - Top View ..;)

Also - May I add seeing many Trucks have Center Shaft Bearing - Total Length of Drive Shaft would be ( Considered )
Both Half's and ADD .500 to the Dia. - due to extra Support OR
Just Consider the Longest Drive - Shaft - Minus .500 Dia. Due to the Presence of a Bearing Support ?

Above ? is for everyone having Any Experience with these Considerations - as many have Changed Rear Axles & Center sections ..
Chasing Down - Eliminating Bad Vibrations !

Re: Checking Driveling Vibration & Calculating It.
 

Looking down at frame rails, center line of trans and center line of pinion should be in line with truck frame rails. Angles auto-magically cancel. More offset of one to the other doesn't matter. If axle is set back to make big thrust angle, or trans and engine are not parallel to rails, then you might see a problem.

WRT to vertical plane, pinion angle is not parallel to ground, trans angle not parallel to ground, shaft must be installed so angles cancel.

Re: Checking Driveling Vibration & Calculating It.
 

This is correct on all counts (except for the "magic" part ;)).

When I referred to the "plan view" that is the "top" view (plan view = view from the top).

So we've answered your question twice now, in a couple different ways.

It is a geometric principle that if a line bisects two parallel lines then the opposing angles will be equal. In the diagram below angles "A" are equal and opposite, as are angles "B". So the offset doesn't need to be the same; only that all of the components need to be square to the vehicle centerline.

Also - the u joints can easily tolerate a difference of +/- 3 degrees; considering the amount of offset compared to the length of the shaft(s) the resulting angle is usually much smaller than this and does not result in a disturbance.

That's why the angles in the top view are generally discounted and all of the focus /discussion is on the view from the side.

Variations of shaft length (in fractions of an inch) are not significant in terms of effects on U joint working angle. Increasing the length of the rear shaft in the basic design can affect launch shudder (a u joint disturbance that manifests itself upon initial acceleration from a stop).

The working length of the shaft is from the center of the u joint cup (front) to the center of the u joint cup (rear).

K

Re: Checking Driveling Vibration & Calculating It.
 

Take a look at this and see if it helps.

There is a section on two piece drivelines but I did not include it here; I try to avoid two piece applications (both at work and at home) and order my trucks such that they get a one piece shaft.

http://67-72chevytrucks.com/vboard/s...d.php?t=522180

If you can follow the logic shown in the flow chart you can fix any driveline problem.

I have a little bit of experience with these considerations.

K

Re: Checking Driveling Vibration & Calculating It.
 

You'd the Man
I understand all Your Input . - I'm stuck with a Two Pc. Drive Shaft - Unfortunately .

Also the Tail Stock on Truck Drive-Line is Not Centered - Neither is Pinion on Rear Gear.

But , from what I'm seeing so Far on this Truck - I can only Hope !
Hence the ?'s - Before I Go and Investigate Deeper .

Thank You - I have just started to set up , some Measuring Equipment .
Currently the Rear Bolt Mounts to the Trans - Are Not Even Bolted Down
NOT SURE - what those Intentions Could Be , so Digging In !

Re: Checking Driveling Vibration & Calculating It.
 

Still Checking Vibration - may have found some Good Vibrations : :lol:
[IMG]http://i1263.photobucket.com/albums/...ps7hoj5g8m.jpg[/IMG]

Re: Checking Driveling Vibration & Calculating It.
 

Looking at all the Angles : Pumpkin Offset 5 inch approx - Pinion comes Back
2.25 Approx . - Picking up that Center Line - to Check - All the Way
Tail Trans Area :
[IMG]http://i1263.photobucket.com/albums/...pslxzndj0v.jpg[/IMG]

Re: Checking Driveling Vibration & Calculating It.
 

Trans _ C/L _ Mission : Nailed It !

[IMG]http://i1263.photobucket.com/albums/...pstgftsqx3.jpg[/IMG]

Re: Checking Driveling Vibration & Calculating It.
 

Same: Center / Line = C/L

Viewed Now on the Carrier or Mid Bearing :

[IMG]http://i1263.photobucket.com/albums/...pszdiuez8d.jpg[/IMG]

Then it's just Steel Rule to Frame and Math , all done . For that Plane !

Re: Checking Driveling Vibration & Calculating It.
 

More Disturbing was the Carrier Bearing Mount with Bearing is Bolted
Square to the Frame - when Nothing Else is ? Seems a Bit Odd ..

Possibly You'll see it these Photo's :
[IMG]http://i1263.photobucket.com/albums/...psckoq1koi.jpg[/IMG]

This one for Sure - Easily Pass Finger on 1 side - No Way on Other ..

[IMG]http://i1263.photobucket.com/albums/...psafql82dw.jpg[/IMG]

What the Hell ?

Re: Checking Driveling Vibration & Calculating It.
 

In the Area - so - Why Not ! "INSPECT" other Items .

https://youtu.be/fuTFBxxk9Fk

Had .018 T.I.R Before - Adjustment .

https://youtu.be/fuTFBxxk9Fk

Re: Checking Driveling Vibration & Calculating It.
 

Rotated Rear Driveshaft 180 Degrees - Tested - seems a little Better . .

Also Found 1 Bad Tire and Rim - Inside on Dual Shot .. 5/8 inch - side to side
1/4 Up & Down . . that certainly does help ..

Re: Checking Driveling Vibration & Calculating It.
 

Found a Nice Drive Line Angle Site . .

http://spicerparts.com/calculators/d...gle-calculator

Re: Checking Driveling Vibration & Calculating It.
 

That site covers everything you could want to know.

Re: Checking Driveling Vibration & Calculating It.
 

I noticed that the spline in your pic is a bit rusty.
I would take it apart, clean it, inspect for wear, and grease it going back together.
Maybe the vibration has something to do with the spline joint not sliding in and out or the rubber in the center bearing support is old and weak, and allowing the driveline to move around?
Sometimes old shock absorbers are sticky in their movements, and bind, causing the rear not to float with the springs as designed.

I just changed the shocks on my tahoe, and sure enough, one of them wouldn't compress. I even put it under the jack point on the rear of the car, and the tire would not touch the ground because the shock was holding solid. Even with the weight of the vehicle.

Would seem to me that if it was designed to be there, then the change that takes place is wear, contamination and age.

1. wear
Check the U joints one at at a time by pulling off the caps, and checkiong the stub ends for wear.
Check the splines for wear
check the trans spline for excessive wear and in the yoke.
2. Contamination
Check that the little boots on the u joints are really sealing out the water, and keeping dirt and other things out.
check the grease in the splines by feeling the lube as it comes off the splines and u joints.
Check for any water getting in where it is not supposed to be.
3. AGE
As we all know, parts that are moving, wear. the wear is exaggerated by the things I mentioned above.
Sometimes parts like rubber and leather, grease, dry out and do not perform like when new.

Like on the cooling system..... Just keep trying things.

Re: Checking Driveling Vibration & Calculating It.
 

Once I straighten the Rear Axle the Spline Joint went back 1/2 inch Farther , then in
Position in Picture Above ( You Mentioned ) - it's almost like the Original Slip Joint
was replaced as it looks to be too Short for a 1 Ton ..
Center Lines is 5.875 - 6.0 it looks to be able to take 7.0 inch Slip Joint - Now ..
U Joints all look Good & Seals ..

Center Carrier is Positioned a Bit Off , as it Not Turned Facing the Pinion enough ..
it's more Sq.
I'll Know more once My New Tool gets here ..

Re: Checking Driveling Vibration & Calculating It.
 

OK Rechecked the Angle again in another Manner to Double Check .

1. First Off - the Center Carrier Bearing Hanger seems a Bit Low .
2. Center Carrier Bearing has .040 Slop - I can shake it .. Up & Down
3. Seals on Joints all seems OK

[IMG]http://i1263.photobucket.com/albums/...psgjkqfxms.jpg[/IMG]

Large Carrier Space - Now Axles is Correctly Located :

[IMG]http://i1263.photobucket.com/albums/...psqehz8dsi.jpg[/IMG]


See Pic's of Angle Checking _ Trans -Bolts you'll see 2 Pic's in Both Directions , also checking My Second Set Up . . ( Making Sure ) Never Hurts - Going down the Wrong Road Twice - Does Hurt . .

[IMG]http://i1263.photobucket.com/albums/...psru7fptgx.jpg[/IMG]

Sec. Check - Reversed Direct of Set Up .
[IMG]http://i1263.photobucket.com/albums/...psateri42m.jpg[/IMG]


Doubled Checked Both Directions & Methods - On Differential .
just Posting 1 Pic.
[IMG]http://i1263.photobucket.com/albums/...psmm9i0yl1.jpg[/IMG]

Re: Checking Driveling Vibration & Calculating It.
 

Now this is Relative to the Ground and Chassis is Sitting on Current Stock Ride Height .
This Doesn't allow for Rear Suspension Compressing over the Last 60 Plus Yrs.

OK so the Numbers as Read :

1. Eng. Trans . 3 Degrees Down
2. 1st Drive Shaft Driven - Trig. Out the Angle to be 4.854 Degrees .
3. 2 sec. Drive Shaft Driven Trig. Angle to be 3.7456
4. Rear Diff. 3 Degrees .

Using the Link I Noted a few post back : Gives
Operating Angles of : 1st 1.85
2nd 1.1
3rd .75

Trig. the Carrier Mount _ to be 3/8 inch Shorter the First Driven goes to 4.35
the Second Drive Shaft - would - move to 4.0 Degrees seeing it's almost Twice longer it moves Less .
This would change the Numbers Too : ~

1st Operating 1.35
2nd Operating .35
3rd. Operating Angle 1 Degree .

Please Add You Comments & Corrective Inputs ..
I Might also be able to Lift the Rear Chassis 1/2" _ 5/8 "at least by Adding Spring Assist Shocks . .
Axle to the Carrier bearing being approx 62 inches . .
Which would NOT change the Trig Angle going to Ground - But - Seems like it would change Chassis Position
Which in Turn Should Rotate the Bearing Carrier just a - Nudge - Less on Driven 1 & More on Driven 2

Re: Checking Driveling Vibration & Calculating It.
 

Made Corrections - Gee'ssss No One caught the 3.3 Degrees - that was in Black & White Guys ` \ : - )

*** Section above is Theory

LOL - I Posted it and even threw up the First Numbers , Haaa Ha at Myself - I Generally always Add the 2 Numbers when
Doing Two Measurements of same Item then Divide them 2 to get more Accurate Number of Item being Measured -
When Measuring from or Going to Items that are a little Difficult to measure or Set up . . Due to Location of Set Up ..
LOL - I was going over the Center Bearing Math - Hit Me - If I add those Two Readings on Transmission shown in Pictures
etc. Those average 270 Degrees ( Which is NO Angle at All ) "AAaannttt" - Tilt - Aaanntt " Tilt !
3.3 Degrees for Engine & Trans

Re: Checking Driveling Vibration & Calculating It.
 

I skimmed through quickly and noticed a couple things:

a) Angles relative to ground do not matter. The u joint working angle is relative to the components affecting the joint (ie, engine trans angle vs shaft angle, or shaft angle compared to rear angle pinion nose angle). Normally one checks off the u joint cup; rotate the shaft 90 degrees and check the angle of that cup and subtract the two. I try to explain the angle directionality as either "holds water" (ex: \/) or "sheds water" (ex: /\).

b) You must have the suspension compressed to the normal ride height. You can't have the rear suspension hanging or all your efforts are wasted.

K

Re: Checking Driveling Vibration & Calculating It.
 

In Your Example Your using the Nose of the Pinion - I Guess - for a Plane then
Checking the Working angles of the Joint ..

In the Real World - We have to Pick a Plane - seeing True Ride Height and Normal Load
would be Std . Stance with Vehicle on the Ground .

Hence the Use of that Plane ..

Trig. the Differences over a 43 " or 25 " inch Shaft and the Height Gage doesn't Lye
it's just Simple Math - U Joint Cups - are Directly Attached too & Aligned with Shaft.

In Case You didn't see the T.I.R - https://youtu.be/hCJSTlRw7Jg

I already had done the T.I.R. of those Area's Several Post Back .. Signalling Good to Go . . for Direct Measurements !