Pinion Angle Issues

[Long Island RT]

Here's my situ:

Bad vibrations @ 65mph+ (felt right on the shifter)

With the car on level ground:
Engine centerline = 5° tilt back
Driveshaft = ½° tilt forward
Pinion = 5°tilt forward

As you can see - I have 5½° angle on the front u-joint and 4½° angle on the rear u-joint with the biggest problem being that they are NOT opposite!
I jacked the back of the tranny until it hit my floor tunnel and got about ½" higher on the mount.

Now:
Engine centerline = 3½° tilt back
Driveshaft = ½° tilt back
Pinion 5° tilt forward

3½° now on the front (better) but now 5½° on the rear.  I didn't get a chance to drive it tonight because of the rain so I'm not sure if it helped.
From everything I read - I still need to get the angles opposite each other regardless, I just don't know how. 
If I shim the pinion up - then I'll lower the rear angle but make the front angle greater.
If I shim the pinion down - then I'll help the front angle but bring the back angle past 6 or 7° - and yet still opposite the front!
I could shim the pinion way up - like 3½° - but that'll put the rear angle in the wrong direction!
I really don't want to raise the rear-end of the car because I'm diggin the ride height.  All these lowered cars must being doing something to correct this. 


What I really need to do is get the tail shaft of the tranny up a LOT higher, but not only will that create some clearance issues on my floor tunnel - I'll have exhaust issue clearance because I have barely ¼" clearance to the floor boards.  Besides - I don't think that a 3½° engine tilt back is out of the ordinary.

What Can I Do?

[greenpigs]

Try this for a start and a few other recent posts on this subject now at Moparts: http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=6271812&an=0&page=0#Post6271812

[Long Island RT]

I did try searching there as well.  Problem is that I never saw any examples where the angle at the tranny joint goes up!  If you think about it, only cars with severly pointed up pinions could cause that or somebody who's car is very low.
Does anybody know what the angle of the engine should be relative to the chassis?  Where would I even measure the body from?

Thanks in advance.

[greenpigs]

It should be parrel to the transmission or 0 degrees, the pinion is what you adjust. Not sure if that is what you are asking?

[elacruze]

Your problem is more likely caused by an out-of-balance tire or possibly driveshaft than the angles themselves.
U-joint angles have to be close, but they DO NOT have to be opposite. To be clear, your transmission tailshaft and axle pinion are usually near parallel, but for instance on industrial and farm equipment a driveshaft may well carry power around a corner. The important thing is that the U-joint angles are near equal and IN THE SAME PLANE.

In the case of an automotive installation, some driveshafts have angles in two planes, vertical and horizontal if the pinion is offset to one side.

Back to your problem. Did you have a new driveshaft made? The yokes must be in line with each other so the front and rear variances are cancelled at the trans and pinion ends. Was your shaft checked for balance and true? Does the vibration go away at 70-75mph? What is the frequency of the vibration? A driveshaft vibration @ 65mph will be a buzz, a tire vibration will be a wiggle.

Driveline vibrations can be difficult to find, but it's only time and science to do so.

[Long Island RT]

Thanks for your responses.

I did do some other tests not mentioned above.  I didn't want to make this into a too long a post so nobody reads it

I read every post hear that had the word "pinion" and "vibration" in it, and there's some real informative stuff.  I learned a lot from RECHRGD's: http://www.dodgecharger.com/forum/index.php/topic,63413.0.html

I also learned a lot from Hurst (formerly Classic Motorsports).  That's where I purchased the TKO 600 and all the accessories to go along.  They have two very good articles on the topic here:
http://www.hurst-drivelines.com/files/Driveline-Vibration-FAQ.pdf
http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdf
That's where I read that the angles need to be OPPOSITE.

Greenpigs - In order to get the pinion parallel to the tail shaft I'd have to point it UP!  The angle on it would be the wrong way.

Elacruze:
My driveshaft was custom built by Inland Empire Driveline- part of the package from Hurst.  Supposedly they electronically balance to 10,000 rpm and use premium Spicer slip yokes and u-joints.  I was going to have it pulled and rechecked locally but then I started measuring angles...
I start to feel the vibration at 65 mph.  At 70 the shifter has a good buzz on it.  At 75 the shifter handle is blurry.  At 80 my rear view mirror is fuzzy.  At 85 the entire car starts to hum.  at 90 I feel like something is going to explode.  My driveshaft is spinning at about 4000rpm at 80mph.  I have not gone over 90 yet.

I have not tried taking off the rear wheels and running it up to speed on jack stands (boy that sounds dangerous).

Hopefully tonight I can give her a spin and see if my tranny shim helped or not.

Does anybody know what the engine tilt should be relative to the chassis?  Maybe I just need to jam that tranny up into the floor some more, but that just doesn't seem right  My driveshaft is already tucked way up into the tunnel.
My car is not even THAT low - maybe 2-3 inches n the back over stock.

More info:
I am using super stock springs that have the front hagers modified to get the ride hieght where it is now.  I have 28" diameter tires that sit about 1 inch up into the wheel weels.

LIRT

[elacruze]

That's good stuff. Just to be clear about your current setup;

Trans output is lower than engine front
Pinion points towards ground not up to car
Driveshaft axle end is higher than trans end

Angles measured from horizontal plane?

With your current untested change, if the difference of angle is to blame I'd expect the problem to get much worse. If it does, then you need to adjust the pinion to match as precisely as possible the angle from the transmission to driveshaft. That is to say, it is the difference of angle from pinion/shaft and shaft/trans that matters, not the angles to horizontal or vertical. Equalize the shaft/axle/trans angles and see if that helps. If not, you may be into some weird balance issues such as in the other links, and you'll have to try the hose-clamp balance method to find that out.

[Long Island RT]

That's good stuff. Just to be clear about your current setup;

Trans output is lower than engine front    Yes - the tilt compared to my level garage floor with the car resting on the wheels is now (after the shimming) about 3° back (meaning the tail shaft pointing towards the ground).  My car does have a rake to it - not sure how to measure rake though.
Pinion points towards ground not up to car  Yes -  rear pinion is now pointed down 5° (again with car planted on wheels in my garage)
Driveshaft axle end is higher than trans end Yes - and that's seems to be the big problem

Angles measured from horizontal plane? All angles were measured with the front wheels on ramps and the rear axle supported by jack stands with the rear tires the same height off the ground as the fronts.  All done on my garage floor.

Thanks again - I see the sun just popped out so a highway jaunt will be in my near future.

[firefighter3931]

If you have the SS springs installed in the upper hole of the hanger to reduce ride height you will have a problem....i had similar issues and ended up installing on the lower hole. 

I'm pretty sure the aftermarket 5 speed transmissions lower the tailshaft to clear the floorpan, which will mess with pinion angle. The simple solution is to measure closely and have the spring perches cut off and rewelded to achieve the desired pinion angle....which is 5-7 degrees nose down with SS springs.


Ron

[greenpigs]

  So Ron what about a lowering block between the third member and spring? I am tempted to get some SS springs but do NOT like rear end in the air that these springs seem to provide.

[Long Island RT]

The test drive went well.

I noticed a big improvement with regards to vibration on the shifter.  There's no loud buzzing or a fuzzy rear view mirror.  Got it (carefully) up to triple digits with no major issues.  Looks like my slight tail shaft shim helped but I'm far from out of the woods.
Now I can't close my hood with the air cleaner on - it must have been very close before!
I still have vibrations - very slight in the shifter but now more pronounced in the seat of the pants.  The vibration this time starts around 65 and stays constant from there on up.
I'm thinking I need to improve the 5½° angle in the rear universal joint.  Problem is, the smaller I make it, the bigger I make the front angle.  Also - I have to lower my trans mount slightly to get my hood to close, making things worse again.

Are there other motor mounts I could use that are thinner?  I think I'll take off the drivers side mount and bracket and see if I can modify it somehow.  Ideally if I could drop the motor about ½" in front, it would help out tremendously.
I really want to get this think butter smooth at all speeds.  With the dough I dropped into this drive train it would be a sin not to have work correctly.

I will try the driving in the driveway thing with no back wheels to eliminate a rear wheel imbalance.

Ron:
I was afraid that might be the issue.  I not only have the springs mounted on the upper hole, I've got a custom bracket the puts the front of the spring even 2 inches higher than that.  All for the same reason greenpigs mentions - I want the traction from the superstock spring with a lower ride height.  And the 5-7° down on the pinion - is that for best traction performance?  Will less put a bigger strain on the u-joints under hard acceleration?
I think it will be impossible to keep my ride height and have a 5-7° angle at the rear pinion while having a vibration free drivetrain...

What springs would you recommend for a 99% driven street car with eventual Mickey Thompson ET Streets out back?  (The old cake and eat it too thing....)

Any other suggestions would be welcome.

Thanks
LIRT

[greenpigs]

I think I'll take off the drivers side mount and bracket and see if I can modify it somehow.  Ideally if I could drop the motor about ½" in front, it would help out tremendously

Ron did that with the Black Pig, 1\2 spacers between K frame. Maybe he will chime in where he got them or they shouldn't be too hard to fab.

[FLG]

You could go mono leaf with caltracs 

[thedodgeboys]

 

[Long Island RT]

Whats the recommended pinion angle with Caltracs and thier mono leaf?

[firefighter3931]

Whats the recommended pinion angle with Caltracs and thier mono leaf?

Calvert recommends 2-3* nose down.

  So Ron what about a lowering block between the third member and spring? I am tempted to get some SS springs but do NOT like rear end in the air that these springs seem to provide.

I'm thinking that the same problem would remain but i don't know for sure....never used lowering blocks 



Ron

[firefighter3931]

The test drive went well.

I noticed a big improvement with regards to vibration on the shifter.  There's no loud buzzing or a fuzzy rear view mirror.  Got it (carefully) up to triple digits with no major issues.  Looks like my slight tail shaft shim helped but I'm far from out of the woods.
Now I can't close my hood with the air cleaner on - it must have been very close before!
I still have vibrations - very slight in the shifter but now more pronounced in the seat of the pants.  The vibration this time starts around 65 and stays constant from there on up.
I'm thinking I need to improve the 5½° angle in the rear universal joint.  Problem is, the smaller I make it, the bigger I make the front angle.  Also - I have to lower my trans mount slightly to get my hood to close, making things worse again.

Are there other motor mounts I could use that are thinner?  I think I'll take off the drivers side mount and bracket and see if I can modify it somehow.  Ideally if I could drop the motor about ½" in front, it would help out tremendously.
I really want to get this think butter smooth at all speeds.  With the dough I dropped into this drive train it would be a sin not to have work correctly.

I will try the driving in the driveway thing with no back wheels to eliminate a rear wheel imbalance.

Ron:
I was afraid that might be the issue.  I not only have the springs mounted on the upper hole, I've got a custom bracket the puts the front of the spring even 2 inches higher than that.  All for the same reason greenpigs mentions - I want the traction from the superstock spring with a lower ride height.  And the 5-7° down on the pinion - is that for best traction performance?  Will less put a bigger strain on the u-joints under hard acceleration?
I think it will be impossible to keep my ride height and have a 5-7° angle at the rear pinion while having a vibration free drivetrain...

What springs would you recommend for a 99% driven street car with eventual Mickey Thompson ET Streets out back?  (The old cake and eat it too thing....)

Any other suggestions would be welcome.

Thanks
LIRT

Ideally, the front and rear angles are supposed to be equal under full acceleration. For example ; if the trans tailshaft was 5* up you would need the pinion at 5-7* down. Your situation is compounded because of the aftermarket trans and the lowered crossmember which aims the pinion down...at least that's what i'm reading correct ? 

As stated before ; the easiest way to fix this is to measure the front angle and figure out exactly what you need out back and reweld the spring perches with the corresponding pinion angle to achieve the desired result. It certainly can be done. 

The Caltrac system is an excellent option but you will run into the same issues that you currently have, i would think.....



Ron

[Long Island RT]

Ideally, the front and rear angles are supposed to be equal under full acceleration. For example ; if the trans tailshaft was 5* up you would need the pinion at 5-7* down. Your situation is compounded because of the aftermarket trans and the lowered crossmember which aims the pinion down...at least that's what I'm reading correct ?    YUP

No matter what I do - with where my tranny is now - and how low my rear is tucked up - I will never get equal but opposite angles on my driveshaft - It's just impossible.   
I'll have to shoot for equal yet the same - but as small as possible.....


So this is what I'm going to try:
1 - Shim the k-frame ½" from the chassis -that will almost put my transmission to driveshaft @ 0° and let me close my hood again.  How that effects my alignment and handling geometry - who knows?
2 - That should move my pinion angle to about 6½° (I'm guesstimating since when I moved the tail shaft up ½" before - it changed the pinion by 1°)
3 - Get a set of shims - I 'll try 2° and 4° out back and see what happens.  One of them should get both angles between 2-3°.

Since the car will not be tracked with slicks and 60 foot times are not nearly as important as vibration free highway cruise- hopefully I can get away with only 2-3° of pinion angle.  If that does work - I know I can switch to the caltracs - Which I think will give me a better ride anywho (if you loosen them up for cruising - right?).  The SS springs do have that dumptruck feeling over the bumps...

[elacruze]

So much has been asked and answered in so many places, I thought it appropriate to add some information directly from the Horse's Mouth, so to speak. From the Spicer website;

"When you rework a chassis or install a new driveshaft in a vehicle, make sure that you follow the basic rules that apply to universal joint operating angles:
RULE 1: UNIVERSAL JOINT OPERATING ANGLES AT EACH END OF A DRIVESHAFT SHOULD ALWAYS BE AT LEAST 1 DEGREE.
RULE 2: UNIVERSAL JOINT OPERATING ANGLES ON EACH END OF A DRIVESHAFT SHOULD ALWAYS BE EQUAL WITHIN 1 DEGREE
OF EACH OTHER (ONE HALF DEGREE FOR MOTOR HOMES AND SHAFTS IN FRONT OF TRANSFER CASE OR AUXILIARY
DEVICE).
RULE 3: FOR VIRTUAL VIBRATION FREE PERFORMANCE, UNIVERSAL JOINT OPERATING ANGLES SHOULD NOT BE LARGER
THAN 3 DEGREES. IF THEY ARE, MAKE SURE THEY DO NOT EXCEED THE MAXIMUM RECOMMENDED ANGLES."

PDF Spicer Driveshaft info;
http://www2.dana.com/pdf/J3311-1-HVTSS.PDF

Now we're faced with a conflict-whether to align the u-joints at cruising conditions or under full power. For me personally, I'm going long mile cruising so I'll align my shaft at perhaps 1/2* pinion down while static so that under cruising power it will be as perfectly aligned as I can make it.
For those who are more concerned with 1/2 a tenth at the track, the 2* pinion down angle applies because the axle rotates up under hard acceleration.

This is a perfect example of 'can't have your cake and eat it too'.

[firefighter3931]

This is a perfect example of 'can't have your cake and eat it too'.

Exactly ! What works for a hard acceleration blast at the track will not necessarily be perfect for everyday driving. There has to be compromise somewhere. 

No matter what I do - with where my tranny is now - and how low my rear is tucked up - I will never get equal but opposite angles on my driveshaft - It's just impossible.   

That's not true at all. A guy i know had the same issue ; pinion angle fubarred up with SS springs mounted in the top hole. He cut the perches off & rewelded removing 11* of pinion angle and the car drives fine now. If the angle is that far out of whack then messing with axle shims won't get you where you want to be, inmo.

I lowered my k-frame with 1in spacers but had to re-align the car. It feels fine at 130 mph on the track. Lowering the k-frame is supposed to improve bump steer from what i'm told but i don't drive mine hard on the street.

The Caltracs when pre-loaded are harsher than the SS springs....that i know for sure.  I haven't tried backing the bars off to compare the ride, however....that'll be next year. Mine has the Mono leafs on it, fyi 



Ron

[Long Island RT]

Thanks guys - I am really learning a lot here 
It's all part of building something custom.  I learned from the beginning that anything custom translates to "does not work until you fix it"!

That's not true at all. A guy i know had the same issue ; pinion angle fubarred up with SS springs mounted in the top hole. He cut the perches off & rewelded removing 11* of pinion angle and the car drives fine now. If the angle is that far out of whack then messing with axle shims won't get you where you want to be, inmo.

Ron,
I see your point with the shims.  I'll use them for testing but once I have the angles worked out, I'll re-weld some new perch's on.  No matter what - with the SS springs I'll need some amount of lowering blocks to get the ride height to my liking.  Then I can always get the monoleaf caltrac system made to order.

LIRT

[greenpigs]

I lowered my k-frame with 1in spacers

Thats what I was trying to say and in my case the wrong word mattered.

[bigbluedodge]

This is a perfect example of 'can't have your cake and eat it too'.

Exactly ! What works for a hard acceleration blast at the track will not necessarily be perfect for everyday driving. There has to be compromise somewhere.  

No matter what I do - with where my tranny is now - and how low my rear is tucked up - I will never get equal but opposite angles on my driveshaft - It's just impossible.  

That's not true at all. A guy i know had the same issue ; pinion angle fubarred up with SS springs mounted in the top hole. He cut the perches off & rewelded removing 11* of pinion angle and the car drives fine now. If the angle is that far out of whack then messing with axle shims won't get you where you want to be, inmo.

I lowered my k-frame with 1in spacers but had to re-align the car. It feels fine at 130 mph on the track. Lowering the k-frame is supposed to improve bump steer from what i'm told but i don't drive mine hard on the street.

The Caltracs when pre-loaded are harsher than the SS springs....that i know for sure.   I haven't tried backing the bars off to compare the ride, however....that'll be next year. Mine has the Mono leafs on it, fyi  



Ron

I agree with Ron

I'm thinking the pinion angle for racing with super stock springs is 5 to seven degrees nose down.....that is, the pinion angle is 5 to 7 degrees down from the centerline of the transmission output shaft.

Now, I know for a fact that when I raised the front spring eye on my stock springs the pinion angle got all screwed up. I wound up using 1" lowering blocks instead. They work fine, even when I added Caltracs.

The idea is to have the centerline of the transmission and the centerline of the rear pinion parallel under load (not lined up but parallel). Any difference in the angle the U Joints make could cause a binding vibration. Also, check to make sure your driveshaft is not to long. It must have some free front to rear movement on the splines in the transmission, I think about 3/4 inch.