Ok attached is the best I could do to draw it out, tried reading the way to do this and confused me (damn simple mind ).

On the left is supposed to be the trans, and the angle is 2.5* tail down from centerline. On the right, the pinion is 1.5* down from centerline. That should give me 4* or 1*? Thats the part that gets me. I have seen where some articles suggest there be a straight line from tail to pinion, but I think the way I have it now, I only have 1* of pinion angle dialed in, which this would lead to my answer why my 60' are so shitty and recently felt a little wheel hop. I need to get this dialed in before friday so I can attempt to be the first LSx in the 9's. Please help. Thanks.

Charlie

FWIW, I will be running 28" 10.5 15" slicks, BADZ Rod ended LCA's, QA1/HAL Shocks, Spohn rod ended TA, TH350, 4,000 stall.

 

The trans mission has nothing to do with pinion angle. What you are measuring is driveline angle.

To set your pinion angle get the car like it sits at the starting line. Place your angle finder on the pinion yoke. Set your pinion at -2 degrees. The ground is your constant.

 

whoa..thats a new one!

 

Okay, not to start anything here, but I told that to Jay to see how true that was and he said that isn't the proper way to measure pinion angle.

Jay stresses how the transmission IS the basis and not the ground.

How can two top suspension gurus disagree on something this important?

 

agreed.. why are we told to measure the driveline angle when trying to set the pinion angle?

 

Explain this car to me then.

You have a car that the crankshaft and trans output shaft are 10 inches from the ground. The pinion yoke is 13 inches from the ground. This has the driveshaft running up hill to the rear end. How would you measure pinion angle and how much would you have??

 

Oh hell no, too many variables and I am not a math guru (having to convert inches of deliniation to angles hurts the brain cell (singular yes) ).

I have also seen diagrams where the measurements are related to the transmission center line, but IIRC it was referring to driveshaft angles and its effects. That being, an excessive angle will wear out the joint quicker than a straighter angle. I would think optimally you would want the the driveshaft to be the centerline from Trans to Pinion during launch, but not to exceed the (putting the pinion nose up). So, setting my pinion down 2* and the trans is 3* down, during launch the driveshaft will have 1* of deliniation, sounds acceptable, but then again I am rambling on with only what I think of the relationship.

No disrespect to Jay at all, but I have got nothing but good advice from Brian and obviously his track results speak loudly for his knowledge. I will reset the angle thursday when I put the new shaft in. Thanks Brian. -2* is referring to Nose down? Dont want to make any assumptions and be wrong.

Brian, what are the effects, other than loss of traction, of having too much or too little PA? I would think too little would increase the propensity to wheel hop, as the axle is rotated and the pinion goes nose up too far? And too little would give a good initial bite but not be able to maintain, therefore spinning shortly after launch?

Charlie

 

Too little will allow the pinion to over rotate. -2* is down yes. Usually I run -2* on a t/a car. Leaf spring cars I run as much as -7*. I havent found the need for more than -2* on any T/A cars. I havent seen them pick up any with more angle.

 

?????

 

Madman, obviously you have tons of real world experience. Have you seen a major difference in traction going from 0 degrees to -2 degrees in an fbod?

Reason I ask is, from a "u joint" perspective (from the manufacturers) they want to parallel the pinion yoke angle to the transmission mainshaft angle to phase the ujoints. So if the trans shaft angle is 1.5 degrees down, they want the pinion to be set 1.5 degrees UP. Just to keep the angles phased for cruising, etc....not for a drag launch where the diff trys to rotate.

So in your above example you would want the trans shaft angle 0 or + (up) some degree so the pinion could be turned down - to parallel it the same degree. (For the ujoint manufacturers)..........

For drag racing traction, Madman's real world experience rules.

My driveshaft is currently zero phased with a 1.5 degree UP pinion angle...I'm going to try the 2 degree down angle for traction.

Thanks for the comments Madman.