Axle perch angle

[Ceedawg]

what is the degree, from pinion centerline, to weld spring perch on housing? B-Body
Thanks

 

[5.7 hemi]

If you’ve got leaf springs, go 3-4 degrees nose down. If a 4 link, 0-1 degree down.

 

[Don selleck]

 

[Glenwood]

depends on the angle of your transmission. My 64 stock rear points up 5 degrees with perches level because my transmission points down also and the angles want to be parallel under acceleration more or less. Also depends on the horsepower being applied and if this is for racing or street. 5.7 Hemi & DVW are good sources for guidance.
I went through this last year when changing perches on a '70 rearend I installed in the 64. No vibration in mine after the change. Check out my thread starting about post 749.

 

[Don selleck]

interesting, I assume type of springs and a pinion snubber would have an effect on the equation? mine is set a 1.34 up and trans is 1.68 down have not tested yet. mine was down at 4. something after i changed to stock springs from super stocks. so according to drive shaft harmonics i shimmed up and got the 1.34.

 

[dvw]

Best to measure. Most perches from the factory are about 5 degrees nose up. Leaf spring race application the pinion needs to be about 5 degrees down compared to the trans output shaft. Zero on the perches should be close. Personally I clamp the loose perches with the housing in the car. Set the car on the ground. Measure and pry or tap on the housing to achieve the correct angle. Then tack weld. Remove the housing and stitch the perches with 1" welds, cooling in between welds. A full weld will warp the housing. If you're making power gusset the ends of the perch at a 45 degree angle to the housing.
Doug

 

[5.7 hemi]

If the nose of the rear is to start with, it will move up more under acceleration. That’s why for a street car, it’s nose down so when you get on it, it meets the level of the trans. Now a 4 link doesn’t “rise” like a leaf spring car, so that why 0-1 degree down is best.

 

[Ceedawg]

Thanks, couldn’t remember whether 3 or 5% This is a street car and every one from the factory where this way, just didn’t have one out where I could measure. The reason Chrysler made those beveled shims was to get it angled back down for racing.
While we’re on the subject, I’m using a 70 b-body Dana in a 66 car, will I have a clearance problem with the 5/8 wider housing?

 

[5.7 hemi]

I don’t think so. But that’s really gonna depend on tire and rim size, back spacing etc..

 

[Don selleck]

 

[Dipstick]

From Doctor Diff:

A-body perch (level): pinion 5 degrees up
B-body perch (level): pinion 4 degrees up
C-body perch (level): pinion 3 degrees up
E-body perch (level): pinion 6 degrees up
FL perch (level): pinion 3 degrees up

 

[Ceedawg]

Thanks, I’ll write that down in a safe place

 

[5.7 hemi]

Why would you want to set pinion angle upwards? When ya nail it, the pinion is gonna rise.

 

[Ceedawg]

The spring is not level at the center bolt, it’s angled up towards the rear of car when loaded, so if you put them level pinion would be pointing into the ground. Measure the front bolt from ground then the shackle at the back. Higher at the back. Also the springs are designed to be run straight (spring eye to spring eye) at normal ride hight

 

[Don selleck]

From Doctor Diff:

A-body perch (level): pinion 5 degrees up
B-body perch (level): pinion 4 degrees up
C-body perch (level): pinion 3 degrees up
E-body perch (level): pinion 6 degrees up
FL perch (level): pinion 3 degrees up

Not to disagree with this maybe i'm overlooking something else that was changed?
at the 1 degree up on my pinion angle i removed the adjustable snubber because it was touching the stop, i have about 3 inches now which seems to be less than i need. at 4 up mine would be nearly touching again. stock springs and shackles. ?

 

[oldkimmer]

The Dr is saying that’s where they were factory, not to put them there.wherever the trans is at the pinion has to be lower a few degrees on a leaf spring car. Example: if the trans is down 3 degrees then the pinion needs to be down 6 or 7 degrees. Pinion always rises up. Kim

 

[bm02tj]

https://www.google.com/search?q=u+j...jAhVriFQKHVoMCesQsAR6BAgEEAE&biw=1440&bih=708

Ujoint angles need to cancel each other or it will vibrate
But you need to keep in mind axle wrap

 

[Crackedback]

From Doctor Diff:

A-body perch (level): pinion 5 degrees up
B-body perch (level): pinion 4 degrees up
C-body perch (level): pinion 3 degrees up
E-body perch (level): pinion 6 degrees up
FL perch (level): pinion 3 degrees up

Yes, this is the perch level and the angle of the pinion which has zero to do with pinion angle in the car. Pinion angle will vary from car to car and is a function of where the trans tailshaft and pinion are pointing in degrees from level.

Sorry Kimmer, If the trans is down 3* you DO NOT want the pinion pointing down 6-7*... that's a net negative 9-10* pinion angle. That setting will wear out u-joints and likely cause vibration issues. I've had some SS spring cars want that much, never saw any street time though, only 1/4 passes.

 

[dvw]

Dr diffs angles are a great starting point for a stock vehicle. As stated the leaf spring (where the housing attaches) does not set parallel to the ground. If you are going to drag race then you need to lower the pinion C/L (down in front) in relation to the trans C/L. 4 degrees works well and doesn't cause vibration during street driving. In the previous example the trans is 3 degrees down in the rear. To obtain 4 degree difference the pinion would point 1 degree down. Thus under load the pinion rises (now 3 degrees pointing up) cancelling the 4 degree split between the 2 angles. Pay no attention to the drive shaft itself. It will only cause confusion. Just work with the trans and pinion C/L. As the rear suspension changes and becomes stiffer less extra pinion angle is needed. IE such as ; 4 link, ladder bar, Cal track cars.
Doug

 

[Don selleck]

wow all over the board, guess it depends on what your using it for, and how much flex you have in the springs that allow the pinion angle to rise under acceleration.