more pinion angle fun

[rockdogz]

I've been reading up on pinion angle, and I still don't get it. :willy:
My measurements are:
drivetrain angle pointing 1.4 degrees down (measured by bottom of oil pan)
rear end pointing 2.2 degrees down (measured across face of rear end housing perpendicular to ground
So is my pinion angle -3.6 degrees?

Some more measurements that may or may not have any bearing:

driveshaft is 3.1 degrees down towards rear of car
ground sloping 0.3 degrees towards rear of car

[race-rodz]

yes...kind of. im not too sure how accurate the oil pan is, if you cant check it at the tail housing on the trans, check it on a machined surface.

if the trans points "down" x degrees, and the rear points "up" x degrees, then the working angle is zero.

1.4* down doesnt sound correct, the drain angle is usually about 3-5* from level, this just happens to be the same as the pinion from verticle.

i cant remember what is the "normal" working angle on leaf spring cars, but i think its about -2-3*

[XcYZ]

FWIW, I recall asking Kyle at DSE what he recommends for pinion angle with his springs and it was -3*.

[rockdogz]

Yeah, I've heard -3 degrees is what you want.
I guess I'm wondering what I have - is it -3.6 degrees? That's what I don't understand... thanks! :D

[sinned]

Kyle's recommendation of -3* is not the working angle. The working should always as close to zero as possible without actually being zero.

All measurements need to be accurate. You need to remove the drivesahft and measure at the tailshaft of the trans and across the pinion face where the ujoints mate up. Also measure the tube itself to determine the working angle. Get all those measurements and I'll put together a small jpeg depicting what you have and why the angles are what they are. It always helps to "see" what you are trying to understand.

[rockdogz]

Thanks Dennis, I will do this.
When you say,
Also measure the tube itself to determine the working angle
does this mean the driveshaft? Because I measured that and it's sloping 3.1 degrees down towards the pinion.

Thanks,

[sinned]

That is what I mean, 3.1 sounds about right.

See if this helps-http://www.onrails.us/drivelineangle.jpg

[Ummgawa]

I am abou to weld my 4 link brackets to my rear end housing,and this is VERY helpful and timely for me. Thanks a bunch. :thumbsup:

[rockdogz]

Ok, my tailshaft is 1.5 down, axle is 1.8 down, and driveshaft is 2.8 down. Is this ok? Where does the -3 degrees come in?

[sinned]

Ok, my tailshaft is 1.5 down, axle is 1.8 down, and driveshaft is 2.8 down. Is this ok? Where does the -3 degrees come in?
The way it sits right now you have a front working angle of 1.3* and a rear working angle of 1.0*. The working angles are not that bad, if you could drop the tailshaft down .5* the front would be perfect. The rear needs some work, you need to get the pinion angle up to 2*. If you can do that you won't have any driveline related issues to worry about. Good luck.

Keep in mind that it is easy to make blanket recommendations, however every car is different and what works well in one will not work as well in another. The main reason for recommending a low pinion angle is for traction at launch, as the pinion climbs it will go positive if you start at over 0 anyways. I would rather sascrafice some launch traction for high speed smoothness. Driveline critical speed drops substantialy with high ujoint working angles. Losing a prop shaft at 100+ would really suck bad.