Pinion angle help

olblue68

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I just bought a 68 Coronet 440/727/8 3/4 that has set in the garage for 10 years due to some electrical problems.

I have got it back on the road but due to sitting way to high in rear I removed the helper springs and installed 1.5 lowering blocks and 1.5 degree shims and it has vibrations at 30 mph and up.

I never drove it before lowering it, I had driveshaft balanced with new ujoints. There is no play in output shaft and pinion bearing feels fine. The engine and Trans mounts are good torque convertor bolts are tight.

I ran car on jackstands with no wheels or brake drums and vibration still there.

The pinion angle is 3 down at Trans 3 up at rear and .5 center of driveshaft.

Help :)
 

Lefty71

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I have to grab the bag of popcorn on this one because I'm right about to the point where I need to check mine....
My understanding is that the front should be 2.5 degrees or less, but not zero.... the rear could be 2-5 degrees nose down depending on suspension and use. These numbers are in relation to the driveshaft, not to the level ground.
I do not understand what you mean by driveshaft at .5.
Hopefully someone that does this often will chime in.....
Also, bear in mind, vibration could potentially be unrelated to this setup of the rear suspension.
Oh, and welcome to the group. Pix are required lol. :drinks:
 

33 IMP

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Which way have you got the shims? If they aren't now, I would put them in to put the nose of the rear down.
Whichever way they are, changing them is a no-cost experiment.
And I'd try it without the lowering blocks too.
Mine, with SS springs.

20191124_100126.jpg


20191124_100112.jpg
 
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olblue68

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Actually did shims both ways and then took them out and nothing changed

I am truly in love with this car but it is killing me
 

Gus chiggins

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Which way have you got the shims? If they aren't now, I would put them in to put the nose of the rear down.
Whichever way they are, changing them is a no-cost experiment.
And I'd try it without the lowering blocks too.
Mine, with SS springs.

View attachment 1342384

View attachment 1342385
Never like lowering blocks. Maybe it's just me, but it felt like driving a mack dump truck.
 

olblue68

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Lefty the driveshaft was only .5 degrees down at the center which pretty sure that means it needs more angle

Here she is

20220814_142009.jpg


20220814_141941.jpg


20220623_193002.jpg
 

69L48Z27

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Tremec has an iPhone app to check driveline angles. Uses the built in level function of the phone, tells you where to place it then tap to record. Once you do all three places it will give you feedback of what’s good and what’s bad.

I would run the pinion nose down 4-5 degrees. The trans and pinion are all relative to height of each. Lowering blocks can change that relatively. Having 1.5-3* at each intersection is what you want. Straight and over 5* are where problems start.
 

Lefty71

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was only .5 degrees down at the center which pretty sure that means it needs more angle
To put it a different way.... how is the trans shaft angle in relation to the pinion angle?? Parallel, like on the same plane but at different heights now? Beautiful car BTW.
 

66/440

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Did you remove the drive shaft when you did the work? Is the drive shaft phased correctly?
 

69 Sleeper Bee

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Looking at your cars ride height now why would you need shims at all ?
Do lowering block kits say to add them ?
 

olblue68

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Looking at your cars ride height now why would you need shims at all ?
Do lowering block kits say to add them ?
I originally ran without shims and had the vibration so did shims hoping that would fix it which it didn't
 

olblue68

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To put it a different way.... how is the trans shaft angle in relation to the pinion angle?? Parallel, like on the same plane but at different heights now? Beautiful car BTW.
pretty sure mine is like the top one right now

phasing.jpg
 

hunt2elk

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Did you remove the drive shaft when you did the work? Is the drive shaft phased correctly?
What do you mean by "phased correctly"? Flip it 180 in the pinion yoke I am guessing? I have never heard anybody having to do that with a balanced driveshaft.
 

FrankenBee

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pretty sure mine is like the top one right now

View attachment 1342493
The lower picture is definitely what you want to strive for. It is important that the center line of the Engine/Transmission centerline is relatively parallel to the centerline of rear differential. For drag racing, you would point the pinion down slightly to account for axle windup under full send, but not necessary on a street car. Axle windup, or a pinion angle that is pointed too far upwards will generally cause a shudder under moderate to hard acceleration from a stop. This being said, it is definitely best to have a little bit of working angle in the U-joints. For process of elimination, make sure the weight of the car is on the rear axle when checking the pinion angle, as with leaf springs the angles will change through the arc of travel. If you have done this and there is not enough working angle in the joints, you could shim the transmission up and rotate the pinion down accordingly. If the vibration still exists, it could be in the shaft, one of the rear axles, or wheels. Phasing of the u-joints refers to the "Clocking" of the saddles welded to the shaft, they should be oriented at 90 degrees to one another. I have seen where shafts have been cut and welded and the saddles are inline, or at a random orientation and this will definitely produce a vibration. Hope this helps.
 

INTMD8

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How about some photos of your angle checking?

Don't see how pinion can be 3deg down, trans 3deg up but also looks like the first photo which is opposite.
 
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