I just put a 9" under my '70 Pro Stock "tribute" car. It's centered on the leaf springs. Exact same measurement from end of housing to edge of leaf spring. Springs were hanging slack when the rearend got set on the spring perches. The perches are not welded on yet, just u-bolts at this time. Wiggled the springs to make sure they were relaxed front to back before bolting things down. Put the axles in, mounted the tires and they clear the springs by the exact same amount on each side. I would consider that centered in the springs. Springs measure same width from front to back so no "side bow" put in the springs doing all the moving to get things where I wanted them before tightening the u-bolts. Everything looks "right" under the car and measures good. If I measure from the outside edge of the tire (my tires stick out slightly so this is pretty easy to do) to the furthest out body line on each side, the tire sticks out 3/4" further on the right side than the left. I measured at several locations (character line above wheelwell, back edge of drip rail, top edge of wheelwell). I did these measurements from a 4' long digital level against the edge of the tire going vertical from the floor. Anyone else ran into this? I realize I'm working with a car that's driven a lot of miles over many years and things move. Any ideas? Anyone measure theirs? Have trouble getting both tires to clear inner lip of the wheelwell with tires under the fenders? Thanks Thanks, SPark
Not unusual...These cars were bent/banged and twisted to make everything fit together while being bucked on the assembly line...Mass production at its finest.
If it's bugging you, you could always move it the 3/8" to center it before you weld the spring perches on...won't hurt anything.
Going to look at the leafs closer. They have been changed and maybe they didn't center the front bushings when they were put together. It's not much but it is noticeable since the first tread runs just below the wheel lip on one side and inside it 3/4" on the other side. Thanks, SPark
Tires are M/T 29/12.50x15 Sportsman Pro mounted on 15x11 Fenton Gyro wheels. They fit and clear all the inner fenderwell at this time. Once brake drums and everything else is on, they will sit 1/2" further out than in the pics. SPark
It really comes down to what the 9" came out of (different driver/passenger axle lengths). If you intend to use the housing without altering it, you're really down to only 2 choices. You can either center the pinion with the driveshaft and have the wheels slightly offset like you have now...Or you can center the wheels and have the pinion/driveshaft slightly offset. The u-joints will still operate just fine if you offset the pinion and center the wheels. The angle would be no different side to side than it would be up and down when the rear travels over bumps and such. Ie...the rear housing moves considerably more than 3/8" up and down with shock travel every time you drive down the street (the driveshaft is rarely, if ever, rotating in a perfectly straight plane). I've always been told...but cannot personally verify, that some cars even came from the factory with the driveshaft offset front to rear like this. If it is a major concern for you, the only way you're going to fix it is to center the pinion with your driveshaft, and then have your axle tubes trimmed and re-welded to match the dimensions side to side. But you'll also have to have new axles if you go that route. Expensive...but it would be dead-nuts on. So it ultimately comes down to what you're willing to live with. The measurement to the spring perches will not really impact anything one way or another. You have 3 fixed points, the pinion, and the ends of each axle tube. You can't change either's location from one another by the location of the spring perches. They're either all centered or they're not. I hope that doesn't come off as a smarta** response, because I don't mean for it too lol... I hope that makes sense...
Doesn't come off as smarta$$ at all. Maybe my question is not fully understood. This is a custom made rearend. It's not taken out of anything. It's all brand new with the exception of the center section. 1/4" wall dom tubes, billet ends, 31 spline custom axles, etc. It was made to my spec to center the pinion in the driveshaft tunnel and make the tires clear the springs. It does that perfectly. My axle is centered in the springs but the springs themselves are not centered in the body is what it boils down to. The right side spring is closer to the outside of the body than the left side spring. The pinion is centered, the tires clear the springs the exact same distance on each side. The difference seems to be the springs are not centered in the car. My main difference on this car vs others I have done, is keeping the springs in the stock location. I've tubbed a '66 Fairlane GTA, my '61 Falcon and built a track T with a custom quick change I did my own axle work on. The difference with all of them was I moved the springs to fit the tire/wheel offset/car. It's not that much difference, I can deal with it in several ways. I was just curious if anyone else had noticed this being a problem with their builds. My Falcon My Track T Thanks for the input, SPark
Wow ... really like the Falcon. Don't worry about perfectly centering the pinion. U-joints need a small bit of offset (side load) to make the work right, either up/down or side-to-side. If you had the rear axle aimed directly at the output shaft of the tranny in both planes, the driveshaft should vibrate.
