Pinion Angle, vibration, confirm my thinking

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aengineguy

aengineguy

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Hi All,

I have extensively read all the threads on pinion angle settings. Experiencing a pretty good vibration at WOT towards top of second gear in a 904. Surely seams like @ drive shaft speed, not wheels and diminishes a little after shifting to 3rd. I can rev this thing to over 6K in neutral, smooth as silk.

Checked my angles last night according to all the info. At front end, Trans up .5 degrees, shaft down 1.4 degrees for a 1.9 degree difference. At the back, shaft up about 1.5 and pinion down about .5 for a 2 degree difference. Therefore currently I am setting at trans to pinion angle of about parallel, which I am thinking is not good static.

I am running Caltracs, so thinking that I have to shim for the pinion angle to rotate down another 2 to 3 degrees to compensate for torque wrap, which should put me back to parallel under hard accel.

Please confirm my thoughts....appreciate it!
 
Changing the pinion angle is an easy way to test your theory. Though this pinion angle caused problem is normally more associated with total shaft RPM, not engine RPM. How is your engine balance? Correct harmonic balancer and/or flex plate weighting? Was your engine recently rebuilt or if you recently bought the car, was the engine rebuilt by the PO?
 
aengineguy said:
Hi All,

I have extensively read all the threads on pinion angle settings. Experiencing a pretty good vibration at WOT towards top of second gear in a 904. Surely seams like @ drive shaft speed, not wheels and diminishes a little after shifting to 3rd. I can rev this thing to over 6K in neutral, smooth as silk.

Checked my angles last night according to all the info. At front end, Trans up .5 degrees, shaft down 1.4 degrees for a 1.9 degree difference. At the back, shaft up about 1.5 and pinion down about .5 for a 2 degree difference. Therefore currently I am setting at trans to pinion angle of about parallel, which I am thinking is not good static.

I am running Caltracs, so thinking that I have to shim for the pinion angle to rotate down another 2 to 3 degrees to compensate for torque wrap, which should put me back to parallel under hard accel.

Please confirm my thoughts....appreciate it!
Click to expand...

don`t quite follow u on all the angles, sounds like u need to raise the engine to get the it and the trans-driveshaft level or thereabouts then check the rears angle.????????guess the driveshaft would have to have some down, to be at optimum "level" when the rear kicks up under hard load. I`m interested in this as, I will be checking all this in the future, keep us posted--------maybe some one that knows can enlighten us!:?-----bob
 
I have CalTrac with mono leafs.They recomend 1-2 degrees down pinion angle. The pinion does not wrap much due to the design. I had too much angle and had vibration going down the highway. I now have 2 degrees down angle and no vibration
 
68gtxman said:
Changing the pinion angle is an easy way to test your theory. Though this pinion angle caused problem is normally more associated with total shaft RPM, not engine RPM. How is your engine balance? Correct harmonic balancer and/or flex plate weighting? Was your engine recently rebuilt or if you recently bought the car, was the engine rebuilt by the PO?
Click to expand...

Thanks 68.....Engine balance is good, zing to 6400 in neutral, smooth as silk. I rebuilt the engine myself with all pretty stinking good parts. Hughes did the balance on the rotating assembly, SFI balancer, PTC converter.
 
famous bob said:
don`t quite follow u on all the angles, sounds like u need to raise the engine to get the it and the trans-driveshaft level or thereabouts then check the rears angle.????????guess the driveshaft would have to have some down, to be at optimum "level" when the rear kicks up under hard load. I`m interested in this as, I will be checking all this in the future, keep us posted--------maybe some one that knows can enlighten us!:?-----bob
Click to expand...

Thanks Bob......I spent over 2 hours reading all the info and threads on this yesterday. There is a ton of stuff on it, but I think I am correct in my suspicions.
 
I assume you had the car up off the ground to be able to do this. Did you have the rear suspension loaded, or hanging?
 
Ted Carlson said:
I have CalTrac with mono leafs.They recomend 1-2 degrees down pinion angle. The pinion does not wrap much due to the design. I had too much angle and had vibration going down the highway. I now have 2 degrees down angle and no vibration
Click to expand...

Thanks Ted,

This is what I am thinking. I have sent an email to Calvert so they could confirm also. What I have read here on this board, is that Caltracs need to be down from parallel about 2 to 3 degrees, nothing like SS springs, due to as you mentioned the tightness of the Caltracs.

By the way, do you know the guys at Carson Valley Transmissions. When I bought the car in Fresno, CA I was driving back to Illinois and had a Baaad vibration in the original 318 engine. I pulled into their shop and 3 guys attacked it, looking over the externals. Could not find anything. Obviously that engine and trans are long gone. I think those guys were into alcohol drag boats.
 
not to discount your theory on pinion angle but have you inspected your u-joints . I have experienced several instances where the rollers begin to gall into the cups. then you get a vibration that comes in goes at a certain RPM. usually found in your Middle speeds between 40 to 60 miles an hour. this won't show itself on a shakedown you'll have to physically disassemble the joints and inspect the crosses. I hope this helps you good luck
 
funwithfuel said:
not to discount your theory on pinion angle but have you inspected your u-joints . I have experienced several instances where the rollers begin to gall into the cups. then you get a vibration that comes in goes at a certain RPM. usually found in your Middle speeds between 40 to 60 miles an hour. this won't show itself on a shakedown you'll have to physically disassemble the joints and inspect the crosses. I hope this helps you good luck
Click to expand...

Thanks funwith.....

Shaft has about 1500 miles on it, brand new by reputable shop who build racing shafts. Did take it out yesterday and look at the needles I could get to without pressing all apart. everything looks good and the SY moves free without any notching. I went with good Spicer 1350's and Mark Williams forged SY so as not to have worries.
 
Have you checked motor mounts, trans crossmember mount etc.? Is there any play in the output shaft bearing in the trans?

Just thinking out loud here.
 
aengineguy said:
I am running Caltracs, so thinking that I have to shim for the pinion angle to rotate down another 2 to 3 degrees to compensate for torque wrap, which should put me back to parallel under hard accel.

Please confirm my thoughts....appreciate it!
Click to expand...

This is what I would do for your pinion angle.

No comment on your vibration.
 
Thanks to the recent posters......

Supershafts, I am going to at least get the angle corrected and see if there is any improvement and then go from there.

Bad Sport, almost unperceivable play in the bushing, mounts are new and good. Although, got me thinking, I do have a tight torque strap on it.

Thanks Cracked....
 
Do you notice the same vibration at speeds of multiples?

In other words, you notice the vibration at 35 mph, do you also notice a similar vibration at 70 mph?
 
Hyper-Performance said:
Do you notice the same vibration at speeds of multiples?

In other words, you notice the vibration at 35 mph, do you also notice a similar vibration at 70 mph?
Click to expand...


No, vibration is only at WOT, coming in at the top of second gear. I could not tell much in third, because I was over the century mark and let off. No vibes in third part throttle at about 80 or anytime, any gear below that speed.
 
I am getting the same thing, ever since I swapped out my pig.

I get a bad vibration under heavy load, which would be when the angle would be the greatest.
 
trapster said:
I am getting the same thing, ever since I swapped out my pig.

I get a bad vibration under heavy load, which would be when the angle would be the greatest.
Click to expand...


If you got the same thing since you changed it, then something is wrong when you put it back in since you didn't have it before.

The angle doesn't change when changing the center.

The vibration would be at it's worst in 1st, that is where the load would be the greatest.

.
 
Supershafts said:
If you got the same thing since you changed it, then something is wrong when you put it back in since you didn't have it before.

The angle doesn't change when changing the center.

The vibration would be at it's worst in 1st, that is where the load would be the greatest.

.
Click to expand...

u ain`t got the cal tracs loaded to hard do u ? wondering ,-bob:eek:ops:
 
aengineguy said:
Hi All,

I have extensively read all the threads on pinion angle settings. Experiencing a pretty good vibration at WOT towards top of second gear in a 904. Surely seams like @ drive shaft speed, not wheels and diminishes a little after shifting to 3rd. I can rev this thing to over 6K in neutral, smooth as silk.

Checked my angles last night according to all the info. At front end, Trans up .5 degrees, shaft down 1.4 degrees for a 1.9 degree difference. At the back, shaft up about 1.5 and pinion down about .5 for a 2 degree difference. Therefore currently I am setting at trans to pinion angle of about parallel, which I am thinking is not good static.

I am running Caltracs, so thinking that I have to shim for the pinion angle to rotate down another 2 to 3 degrees to compensate for torque wrap, which should put me back to parallel under hard accel.

Please confirm my thoughts....appreciate it!
Click to expand...

Your crank/trans centerline and pinion angle are parallel. This can cause harmonics and increased u-joint wear. You are right to shim the pinion 2 degrees down.
 
jbc426 said:
Your crank/trans centerline and pinion angle are parallel. This can cause harmonics and increased u-joint wear. You are right to shim the pinion 2 degrees down.
Click to expand...

They are SUPPOSED to be parallel. Only reason its recommended "down" from parallel is that it will run OK at 2 or so under light (cruise) loads. Under WOT, it's "estimated" that the pinion will wrap up to "nearly parallel."

What they are NOT supposed to be is "in the same plane." That is, aligned not only parallel but forming one single straight line, IE both joints operating at zero angle

A little reading from Dana / Spicer

[ame]http://www2.dana.com/pdf/J3311-1-DSSP.pdf[/ame]
 
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