Pinion angle experts, please step in
05-12-2017, 09:01 PM
#1
Pinion angle experts, please step in
Noob here, need some pinion angle help.
Tranny points down 6 degrees
Rear end points up 4 degrees
What shim size do I need to be good to go? I will make over 500hp soon, so I want the angle to be good for racing and laying the power down
Tranny points down 6 degrees
Rear end points up 4 degrees
What shim size do I need to be good to go? I will make over 500hp soon, so I want the angle to be good for racing and laying the power down
05-13-2017, 11:23 PM
#5
The angles need to match opposite each other. I would not recommend wedges in the rear end - they always fail and become dangerous. The easiest solution here is to shim up the back of the transmission with aluminum blocks between the tailshaft housing and the rubber mount plate. Remove the nut holding the mount to the crossmember and then use you floorjack with a piece of wood on it to lift the trans by the pan until it gets to 4 degrees. (May be a good idea to loosen the exhaust too.) Measure the gap once you get to 4 degrees and that will be close enough to order some aluminum. Put the nut back in the crossmember - can't shim there because the captive bolt in the mount is too short. You'll need 2 longer metric bolts for the tailshaft housing.
Some will argue that the 2 degrees it's off right now actually favors a good launch because the springs will wrap and the angles will match under hard power in first gear. I don't agree with that for daily driver - racecar, sure. The vibrations in the driveline caused by the angle difference are felt most at high driveline rpm and vehicle speeds. At those speeds the inertial forces at work causing the vibrations is absolute hell on gears, splines, and u-joints. At cruising sped you want it to be completely free of vibration, so that inherently means those angles need to match opposite of each other. As for the spring wrap - control it with links if the angle change is too great. Get some GoPro footage under frame of a launch to determine that.
Some will argue that the 2 degrees it's off right now actually favors a good launch because the springs will wrap and the angles will match under hard power in first gear. I don't agree with that for daily driver - racecar, sure. The vibrations in the driveline caused by the angle difference are felt most at high driveline rpm and vehicle speeds. At those speeds the inertial forces at work causing the vibrations is absolute hell on gears, splines, and u-joints. At cruising sped you want it to be completely free of vibration, so that inherently means those angles need to match opposite of each other. As for the spring wrap - control it with links if the angle change is too great. Get some GoPro footage under frame of a launch to determine that.