Pinion angle again

Re: Pinion angle again [Re: Quicktree] #1819938 05/06/15 02:08 AM 05/06/15 02:08 AM
Joined: Dec 2005 Posts: 11,542 Fulton County, PA C CMcAllister Mr. Helpful
CMcAllister Mr. Helpful C Joined: Dec 2005 Posts: 11,542 Fulton County, PA	Originally Posted By Quicktree Originally Posted By CMcAllister A 9" Ford with a 32" tire has the pinion about 13" off the ground. Danas and 12 bolts will be higher. In a stock front end backhalf car, that has likely been lowered and with the engine and trans in the original location, the front u-joint will likely be lower than the rear. Typically in the stock location, the engine/trans will angle down front to rear about 2 or 3 degrees. In this situation which is very common, in order to make the pinion and tailshaft parallel requires the pinion angle to go positive which you just don't do. It is not unusual in these cars to end up with what is called the "broken back" configuration. Not the optimum set up, but many times you have to compromise and do the best you can with what you have. The alternative is to relocate the engine/trans mounts. If you are building a car ground up, these things are taken into account and positioned correctly, but in a stock bodied, back half car, you usually don't have the luxury of everything being in exactly the right place. I'm not saying the parallel tailshaft and pinion configuration is wrong, because it is the most correct way to set the driveline up. I'm just saying that sometimes you can't get there and you can't set-up the pinion angle incorrectly to make it happen. ok when you say the tail is lower, give me an angle on the trans? is the tail pointing up? how many degrees? Typically on a backhalf car because of a taller tire and lowering of the car, the rear axle is higher in the car than original. Yes, typically the engine/trans (tailshaft) is 2-4 degrees down from front to rear on stock mounts. The OP says his is 4 degrees down. As a result of the rear being higher in the car, the front u-joint ends up lower than the rear u-joint. Often I find the driveshaft very close to level with the tailshaft down a couple of degrees and the pinion angle also down a couple of degrees as it should be. Total difference between the tailshaft and the pinion ends up being 4 or 5 degrees, maybe more. This is the "broken back" configuration. Lots of cars running like this and I see no problems as a result as long as it doesn't get to far out of whack. Raising the back of the trans on the mount can help, if there is room to do that. If the results don't match the theory, change the theory.