Help needed pinion angle

[Jc cooper]

Could us some help with pinion angle calculation on 67 Belvedere 440 with 8.750 rear diff vibration on deceleration at 75 mph

 

[493 Mike]

There are plenty of tutorials on line explaining the process.
Mike

 

[Sixpactogo]

There are tons of threads dealing with your issue. First step is to get a digital angle finder and get some angles of the drive line. Off hand, a deceleration vibration tells me you need to tip your rear end up in front a couple degrees.
After mulling this over, I'm wondering if you made any changes, like new leaf springs or something to change the angle. Quite possibly you only have a dried up universal joint if no changes were made.

 

[Cranky]

What are your numbers now??

 

[5.7 hemi]

I like the pinion 3 degrees nose down. What is yours?

 

[hunt2elk]

If it makes noise on deceleration you need to raise the pinion. Pick up a 2.5 or 3 degree and give it a try.

 

[Jc cooper]

What are your numbers now??

4* down on drive shaft 1*up on pinion

 

[threewood]

4* down on drive shaft 1*up on pinion

You need the engine/trans angle and rear dif angle to get a reference. At wot the angles should be parallel. So if trans is down 3° the differential should be 3° up.

Here is how I did mine on my 62...

 

[dvw]

Pay no attention to the drive shaft. Measure the trans. Then measure the pinion and compare. The engine/trans will be roughly 2.5 degrees positive (up in front). Ideally under acceleration the rear pinion should be the same. However leaf springs wrap up. You can easily get away with 3-5 degrees additional negative angle at the pinion. So looking too match the engine/trans center line to the pinion center line, here is the math. Assuming 2.5 positive at the trans (or what ever number you measure). Lets say we want an additional 4 degrees negative at the pinion to allow for wrap up. So +2 .5 - 4 = -1.5 at the pinion (pinion down at the front). Now under acceleration the 4 degrees cancels out with spring wind up and both the pinion and
engine/trans center lines are parallel.
Doug

 

[oldkimmer]

Three wood, that’s totally *** backwards. The pinion raises under acceleration. Tranny down 3. Pinion should be do 4.5-6. Kim

 

[Sixpactogo]

Three wood, that’s totally *** backwards. The pinion raises under acceleration. Tranny down 3. Pinion should be do 4.5-6. Kim

Threewood is correct. His reference is under Wide open Throttle. (wot) Although it is pretty hard to get those measurements at that time, he is saying the angles between engine/trans and pinion should equal zero at wot. Driveshaft angle does not come into play.

 

[bm02tj]

Threewood is correct. His reference is under Wide open Throttle. (wot) Although it is pretty hard to get those measurements at that time, he is saying the angles between engine/trans and pinion should equal zero at wot. Driveshaft angle does not come into play.

If under wot then yes it is correct but he did not say if static or wot

 

[Sixpactogo]

If under wot then yes it is correct but he did not say if static or wot

Read sentence #2 again.

 

[oldkimmer]

And just how is he measuring that at wot? No other way to tell for sure. Unless he has a crystal ball. Kim

 

[Sixpactogo]

And just how is he measuring that at wot? No other way to tell for sure. Unless he has a crystal ball. Kim

I don't think he was measuring the angle at WOT. He was just making a reference to the fact that both should be parallel at that point. Where you guys are getting confused is the fact that he didn't mention axle windup and or adjusting the angle to make up for it. I was just saying that his statement is correct. It just doesn't tell the whole story.

 

[493 Mike]

OK. Let me throw a monkey wrench in here. Can I assume a pinion angle the same as the trans angle if I had a Cal Trac setup?
I think so.
Mike

 

[threewood]

Three wood, that’s totally *** backwards. The pinion raises under acceleration. Tranny down 3. Pinion should be do 4.5-6. Kim

The description is 100% correct. 3° down / 3° up = parallel is ideal at wot.

Axle wrap will be different for different springs and how much power is thrown through them.

 

[oldkimmer]

If the trans is down -3* and the pinion is up +3* u r at +6*, there is no way it will cancel themselves out the pinion is already the wrong way. Am I missing something? Kim

 

[bm02tj]

The point is the center line of trans and center line of diff need to be as close to parallel at WOT so depending on springs and power the pinion needs to be 2 to 6 degrees down to counter axle wrap

 

[oldkimmer]

The point is the center line of trans and center line of diff need to be as close to parallel at WOT so depending on springs and power the pinion needs to be 2 to 6 degrees down to counter axle wrap

U r correct. Kim