Correct pinion angle and how to read it

[shadango]

Well, winter is getting close to an end....

That means I will soon be ordering my new rear chunk with 3.55s/SG in it.....

To go along with that I am planning on having my driveshaft balanced....

Also, last fall I found a (really) bad rear ujoint after only a summer or two.....I am wondering if my using the add-aleafs in the back , which gave me more lift than super stock springs do, are the culprit.....I dont have any NEW vibrations or anything.....just the dead ujoint.....and I have a sneaky suspicion that my front ujoint may now have some play in it.....either that or the yoke itself is sloppy on the tranny output shaft.

I found an article online about checking angles using a level, a plumb bob and a ruler, but it seems to require getting the car on a level surface....Well, my garage floor isnt level (slopes toward center/drain)...plus I dont know if I want to reply on my math skills....LOL

So, as my entry for the "dumbest question of the year", isn't there a tool that can be used to check the angle quickly?

I am considering dropping the rear back down an inch or two, but not sure what springs will accomplish that so thought I could at least temporarily shim the rear and the tranny as needed to correct the angles some....

What is the easiest/fastest way to check the angles when you dont have a level surface to work on?  9Ok, technically I guess that is TOW dumb questions...LOL)

[Strawdawg]

I use a magnetic angle finder just like the one pictured in this link    http://www.stu-offroad.com/axle/pinion/pinion-1.htm

attach it to the bottom of the drive shaft and read the angle, then attach it to the lower cap on the u joint and read that angle..then compute the difference.   The floor does not have to be absolutely level as the angle tends to remain unchanged between the shaft and the pinion.

here is another article with some drawings   http://www.wolferacecraft.com/pinionangle.aspx

The larger the angle, the faster the joint wears out.....

[Strawdawg]

A different, more complicated way is shown here   http://www.fordification.com/bumpwiki/index.php?title=How_to_Set_Pinion_Angles

I suspect this is probably closer in a theoretical sense, but, I also suspect most do it by the driveshaft versus pinion angle shown in the wolfe link above. 

[shadango]

Thanks guys

In looking locally for the yellow one, a local hardware guy turned me on to this one:

http://www.rockler.com/product.cfm?page=22143&filter=magnetic%20angle%20cube

Its usually $40 but on sale at a vendor here for $20......does the math for you..... !

I always like a cool gizmo/tool...and this seems like it would work...

[brads70]

Thanks guys

In looking locally for the yellow one, a local hardware guy turned me on to this one:

http://www.rockler.com/product.cfm?page=22143&filter=magnetic%20angle%20cube

Its usually $40 but on sale at a vendor here for $20......does the math for you..... !

I always like a cool gizmo/tool...and this seems like it would work...

Wow $20 I'd  buy one at that price! 

[Strawdawg]

I bought one that came with an attachment for measuring camber and caster....I have used it for pinion angle as well as the sears magnetic angle finder

[brads70]

I bought one that came with an attachment for measuring camber and caster....I have used it for pinion angle as well as the sears magnetic angle finder

Got a picture?   Does it screw onto the end of the spindle or take off the grease cap and a magnet sticks to that surface?

[Strawdawg]

Brad, no it is more simplistic than that altho one can remove the dust cover and lay it across the end of the hub.

I was looking for one of the old bubble style that you put up against the end of the hub which always worked pretty well when I saw this one.....

He was having a sale I paid something less than his current price  as i recall.

You could easily build one yourself if you find the digital level....I see they now have them that go onto the end of the hub but those seem to be awfully expensive to me....

Anyway     http://cgi.ebay.com/ebaymotors/Tenhulzen-Automotive-Camber-caster-alignment-gauge-_W0QQcmdZViewItemQQhashZitem4aa8d44305QQitemZ320660062981QQptZMotorsQ5fAutomotiveQ5fTools#ht_1278wt_1167

[brads70]

Thanks for the link! This is what I have now....
http://www.longacreracing.com/catalog/item.asp?id=129&catid=5

[Strawdawg]

yep, I was looking for an used one of those when I saw the digital one.

The Longacre works very well from my past experience.

[shadango]

Ok...used the new gizmo and.....YIKES!

About 5.75 degrees on the rear....i know thats waaaaaay too much.

So I guess shimming is my next step.

For those who have done this before....any tips?   How do I figure out what shims to use?  For my situation I know they have to go in from the FRONT of the mount so the yoke tilts UP....

Are shims degreed? Or just sized in thicknesses?
************
EDIT

Never mind re: that last question....I see on Summit they sell they in 2, 4 or 6 degree increments.

So, question...which shims would you guys go with?  4 degree shims will bring it down to about 2.75 degrees.....is that ok?

Also, when using shims, does the locator pin get replaced or something to allow for the shim?

yeah, I know....dumb questions....LOL

I cant remember what the locator "pin" looked like when I had the spring pack apart to add the add- a leaf.....

*****edit 2

Ok, now hold the hell up.

Found this article

http://www.moparmusclemagazine.com/projectbuild/mopp_0707_mopar_rearend_replacement/installation.html

IT says "Leaf-spring cars usually require between four and eight degrees of positive pinion angle (nose of the pinion toward the ground) to hook up properly off the line."

So I am ok then at 5.75 degrees?   I stuck a socket to the gizmo and measured at the ujoint cap on the rear and and then on the driveshaft......zerod the gizmo on the socket, then took the reading on the shaft.....5.75 (or so). Is that the measurement they are talking about in the article? Or am I reading it incorrectly?

Yes, I be confused now.

[Strawdawg]

assuming that you paid attention and know that is a minus 5.75 degs, you should be fine..personally, I like a bit less on a street car with an automatic as they tend to "hit" more softly than a stick and therefore need a bit less pinion angle...  No sense in wearing out u joints in the name of something that might be unimportant unless way off or in very high hp cars.

I would take issue with the statement "to hook up" as pinion angle has nothing to do with traction, it merely is intended to line up the drivetrain with the pinion shaft under power so that maximum potential power is applied to the rear gears rather than some being absorbed by the angularity of the driveshaft.  I have never seen this claim by experienced chassis guys, but, I don't know every chassis guy out there   science would not seem to support that claim.

I am guessing that if there is too much angle, the shaft/pinion might bind/unbind and cause a jerky transfer of power, but, I am not sure this has been documented.

[brads70]

Drag racing I'm lost...., circle track is my stronger point. With circle track pinion angle is used to get "bite" off the corners.

[Strawdawg]

Brad, here is a page I copied out of Dave Morgan's Door Slammers.     http://www.vortexbuicks-etc.com/pinion_angle.htm

It might help to remember Dave is talking about strip set ups here.  Kinda interesting that he mentions too much angle can cause tire shake.

[shadango]

assuming that you paid attention and know that is a minus 5.75 degs, you should be fine..personally, I like a bit less on a street car with an automatic as they tend to "hit" more softly than a stick and therefore need a bit less pinion angle...  No sense in wearing out u joints in the name of something that might be unimportant unless way off or in very high hp cars.

I am surprisd that I fall into the "desired" amount ...almost exactly in the middle.

I thought for sure I was way over.......

By "minus" you mean that the pinion is pointing down to the ground, right?  I used the bottom surfaces of the ujoint and shaft to measure since it was easier to get to them...the gizmo I bought works both ways...