This has been hotly debated as to the best, simplified answer available. the best way i can describe it is that the drive shaft should "jog" like when you give directions and you say "head east 3blocks, little jogs to the right, then keep going east" if the tranny is higher than the rear, the driveshaft would obviously point downhill. at the other end, the joint should turn back uphill (returning to level-ish) to connect to the rear axle. The two angles of the ujoints (front and back) should be identical, otherwise you get vibration. the 2-3 degrees of down angle is from people giving the rear a little extra dangle to the nose of the differential so that it will come UP to the correct spec under acceleration (drag car) or constant highway load(cruiser). you do not want to set any angle by comparing to the ground cuz the driveshaft doesn't car what's under it. The angles of the zig zag must be the same. (guess that's the easiest way i can say it)
then the zigzag just goes the other way, but the relationship of the ujoint angles is the same. if the shaft goes up hill by 3 degrees then the rear ujoint should have a 3 degree drop at the rear under power and at ride height. angle mismatch is what causes vibration at speed that you can notice by getting on and off the throttle edit: you must be looooooow. is it your avatar? pics?
Normal cars have the engine and trans slightly lower in the rear, then the carb mounting flange ends up being fairly level. The U-joint angles should be opposite and would therefore cancel out each other's pulses. But; when you get into setting up a very low car the situation get's sticky because the trans ends up pointing directly at the pinion, and under no circumstances should you have zero angle on the U-joints, as this will cause brinnelling and spells faiure. Ideally U-joint angle should be at least 3 degrees, but not more than 15.
brinnelling and spells faiure. Ideally U-joint angle should be at least 3 degrees, but not more than 15.[/QUOTE] Brinnelling, now your just showing off.
What kind of rear suspension are you using? All of the above thoeries may or may not be correct depending on suspension type.
the pinion angle on the differential sould be the same angle the engine and transmission are mounted in , say the engine /trans are mounte 3 degrees down in back the pinion should be 3 up but the drive shaft should never be a straight line through both centerlines. other wise you get what unclee said lol . with a 4 link the pinion angle won't change on acceleration as the 4 links hold everything constant . the ones that changed were the leaf spring cars when the springs would wrap up as the rear end tried to twist . thats why the came up with traction bars
One chart gives the angle for 4 Link and the other Ladder bar. What would the parallel leafs be ranked under?
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