Pinion angle
 

So I have been destroying driveline parts and am going to get a Mark Williams drive shaft, but I am also trying to dot my i's and cross my t's to figure out any contributing factors. My Question is this in the attached links below in regards to pinion/operating angle they seem to contradict each other, what is the ideal setting of the driveline?. In my car I have the tranny 5 degrees down(-)as OEM and the pinion down 1 degree(-) as recomended by the suspension supplier. In the Buick tech link the author talks about the driveshaft being zero and all angles added together for the total number which should be less than 15 degrees. The M/W link says the tranny and pinion should be opposite (one down(-) and one up (+) )of each other. So that would mean i should have my pinion set at 5 degrees up (+) right? that seems back assward to me as the pinion would move up under load exagerating the setting am I wrong?

http://www.buickperformance.com/Pinion.htm
http://www.markwilliams.com/driveshafttech.

Re: Pinion angle
 

No ,you are right. The author's explanation is confusing you, that's all.
If the drive shaft runs downward from the trans, as in most cars and trucks, then the pinion has to run uphill, front to rear. That provides an opposite angle to the rear u joint.
If the angle was the other way, then the drive shaft would whip like a jump rope; That is until it exited the car.
You really just need enough negative pinion angle so that, under power you don't cross the zero point . How much movement there is, depends on the type of suspension, for one thing.

Re: Pinion angle
 

This is all contingent on the way that your rear is attached to the frame IE ( rubber will move more than poly, and poly Will move more than solid mount) Ideally you want your rear pinion angle, and your trans angle to end up parallel under load. So you say your trans is 5* down. Depending on how much your rear pinion will move up under load, you want it to end up 5* up (trans and rear will be parallel)..... So I would say that you should start with your pinion at (from) 0* to 2* up... Then under load it will move up a few degrees, and get it to the 5* up that you want.
This is kind of confusing..... ;-)

Re: Pinion angle
 

Most people I know run the engine/transmission at zero or a couple of degrees up hill. Then run the rearend a couple of degrees or so down hill. The force rotating the rear end, unless it is mounted entirely with solid bushings or spherical rod ends, will cause it to go from a couple of degrees down hill to close to zero. It will rotate even further in some leaf spring cars.

I don't particularly like running the engine/transmission pointed downhill towards the rearend, although some people seem to make it work just fine. You'll note that the factory often placed shims between the transmission mount and the transmission to raise the rear of the transmission up. I've solved a lot of vibration and breakage problems by simply raising the rear of the transmission a little. I always use a urethane transmission mount, or two worm gear style hose clamps on a good rubber transmission mount, and never use a solid transmission mount.

A u-joint requires a couple of degrees of angle in order to make the needle bearings move, or it will quickly develop wear issues. If the only concern was how efficient it would transmit power, then you would want the u-joints to be at zero while under power. If you did that, u-joint life would be fairly short, and there would be all sorts of vibration and flex problems.

You will never achieve the ideal shown in the Mark Williams catalog with a Stock or Super Stock car. You simply cannot keep the centerline of the engine/transmission and the centerline of the pinion perfectly parallel. If you could, plenty of angle would be created when the rear suspension separated under power.

Re: Pinion angle
 

The rear suspension in my car is a Dick Miller Racing setup ,solid lower bars with Poly type bushings and adjustable uppers with a heim and a poly bushing. My tranny mount is a polyurethane piece. He recommends negative 1.5 to 2 degrees (down) on the pinion, and says nothing about trans degree's. So if all things being equal I should adjust my tranny to be 1.5 to 2 degrees positive (up) as Alan sugested?

Re: Pinion angle
 

That's a place to start, at least in my opinion, for whatever that's worth.

Have you taken your springs and shocks off, and used a floor jack to move the rearend through it's travel to the limits to make sure there is no binding, and to see how the pinion angle changes? You should make sure you check it all carefully, especially at the point where the car launches. The rear suspension should separate in order to plant the tires, and you need to check the pinion angle with the rearend at the point of its travel that it is at when the car launches.

Have you checked all of the attachment points for the suspension, and all of the weld joints in the rear frame? You need to make sure there's no flexing or cracking going on back there, it is not at all uncommon to see things moving around back there when one of those cars is raced.

Re: Pinion angle
 

I have checked the diff for range of motion but not for pinion movement, I did an initial check of the chassis and on the surface everything seems ok. I am going to look at the mounting points closer, I'm kind of hoping I find something broken as this problem rose up from nowhere it seems. Upon talking to other stocker guys many seem to have run or are running the stock oem shafts with little to no problem. I really appreciate all the feedback and opinions keep them coming ,I dont want to add to the expensive pile of crap on the garage floor. haha

Re: Pinion angle
 

Dion,
That would be in relation to the driveshaft, not the ground. Had a Wildcat that I think the pinion was actually nose up in the car, but still -2 degrees pinion angle vs drive shaft. I have another brand of those that raise the mounting point of the upper arm, do these?

Re: Pinion angle
 

Thats right my degree measurements are off the tailshaft housing and pinion yoke, all relative to the driveshaft. The suspension has the so called 'no hop' bars which raise the upper bar mounting location, the left bar is the pinion angle adjustment and the right hand bar is the preload adjustment.

Re: Pinion angle
 

Dion,

Do you have the actual degree readings off of the trans, the drive shaft, and the pinion?