Bad vibrations (Part 2!)

[Dave145]

Yes I'm very sure I Know how to measure pinion angle.

I will get one when I get out there soon

 

[Dave145]

Here is one of the axle in the saddle.

 

[Dave145]

Here is the pinion and driveshaft

 

[5.7 hemi]

Holy ****! Hit that with a power washer and degreaser!! Do it, do it noaw!

It’s pointed up, get some shims.

 

[Dave145]

Yeah that thing is sludgy. Yet the underside of the car is clean as can be.

I loosened up the rear end and rocked that car back and forth and now see what everyone means by axle shims. The resting angle off the pinion is 3.5° upward. From the sounds of it, I want about 4° or so downward...correct? Just trying to figure out what thickness of shim I need.

 

[5.7 hemi]

Correct.

 

[Dave145]

What degree shim would you personally put under this car first to establish a base line angle? Seems like a 7° shim to tilt it downward, but would a 4° final downward angle come up enough under acceleration and cruise conditions to satisfy the u joints in their 1-3° angle range?

 

[5.7 hemi]

Street car with leaf springs 4-5*, 4 link 0-1*, so if yours it at 3.5* up a 7* shim should put you at 3.5*-4* down. This will allow the pinion to rise as normal and not vibrate making your u-joints happy.

 

[Dave145]

Awesome I will see if I can find a set and report back!!

 

[Sixpactogo]

Dave,
I would not start out with a 7 degree shim. 4 degree shim is about all you can put in there without adding a longer bolt thru the spring because you won't have enough stud left to fit in the perch.The other option would be to cut the perches off and re weld them. I would try a 3 or 4 degree to start with. Also it appears you will need a pinion seal too since it appears to be leaking.

 

[Fran Blacker]

deleted

 

[Sixpactogo]

As for your pinion seal. I'm guessing your 3rd member is a 741 case. Make sure you get a seal for the correct case. They are not all the same.

 

[747mopar]

This shows the importance of correct angles.

 

[Dave145]

Yes the pinion seal does seep and it's rather annoying. I've been putting off replacing it until I rebuild the rear end to get rid of the 2.75 gears back there. Yes it's a 741 case...good call!

Supposing I get a longer center stud, which I'm not adverse to doing, would the higher degree shim still be adviseable? How much does the rear end move when the car is driving? A 4° shim would net me with a total of -1° at the pinion. Would that still be enough to make it go down the road smooth?

 

[5.7 hemi]

A 3-4* shim would only bring to O*. He needs to get nose down, so if there isn’t enough center pin for a 7* shim, it’ll be cut off wheel time.

 

[5.7 hemi]

It would be better, but not ideal.

 

[Dave145]

My new springs appear to have a bolt in the center, as there is a nut hanging down. Couldn't I just take the nut off and use a punch and hammer to pop it out?

 

[5.7 hemi]

The top will be a “cone”.

Help me out here, is this the first Mopar you’ve owned? I’m asking cause a lot your questions seem to geared toward someone that is new to these cars. Not a big deal either way, cause hey, if ya don’t ask, how do ya learn?

You can use some vise grips to hold the top and zip it off with an air gun, but use a clamp to hold the pack together.

 

[Dave145]

I have owned a few, but i have never dealt with driveline issues before. I can handle motor/trans work fine amongst body and paint stuff, but driveline stuff is pretty new to me.

I used to own a '72 D100 with an 8' step side. Neat truck, but the PO ghetto rigged it so terribly that it was falling apart. Sucks, because I have yet to ever see another one.

I also still own my '76 Dart. It was totaled last year due to some dumb broad on her cell phone rear ending it at 45mph and making the spare tire well meet the gas tank. The wreck stuffed the rear doors into the quarter panels so I can't even get them open. The rear frame horns were mangled above the rear axle. The car took the hit really well FWIW, and both my passenger and myself walked away from the wreck.

This '64 Polara has been a real learning curve for me!

 

[Paul_G]

http://www.wolferacecraft.com/pinionangle.aspx

Guys, slow down here a little. There is incorrect information being passed out. The link above is very important. The angle of the transmission yoke and the angle of the pinion yoke only have relation to each other, not the ground. The pinion yoke does not point down in relation to the ground. The picture of the differential above means nothing in relation to the ground. The pinion will never point down in relation to the ground.

With relation to the ground the transmission yoke will point down in most cases, about 4 degrees, the pinion yoke will point up in most cases usually about the same amount, 4 degrees. The two yokes must be at an equal but opposite angle to each other. Trans pointing down, pinion pointing up, both by the same amount but opposite. Because the trans is generally higher in the chassis than the rear axle, the drive shaft then will have a natural pitch down toward the rear axle. The angle between the drive shaft and both of the yokes must also be considered. Keep it under 2 degrees.

Because leaf springs will wrap, drag racers like to have the pinion a few additional degrees down in relation to the trans yoke. When the springs wrap up under power the pinion will naturally rise and correct to the desired angle, which will make the two angles equal but opposite, and only under full load, a drag car. A street car is different than a drag car. Because the springs will naturally wrap somewhat, it can be wise to give the pinion an extra couple of degrees down in relation to the trans yoke, but no more than that.