this is a little different. and sorry, I know pinion angles have been covered ad nauseum, I just spent an hour reading through at least 100 past post on driveline angles, but this seems to be debatable. My 37 ford has always had a driveline rumble, I bought it as a roller from a friend years ago who set the rear end with the Pinion DOWN 3 degrees and the engine down at 7 degrees. Wrong for sure, I know the usual way with a centered pinion rear is 2 or 3 degrees UP at the pinion for 3 degress DOWN engine angle. so I figure its probably why the noise. anyway, been fooling with my roadster and really quit driving the 37 much because I knew it wasnt right and something was going to break if I didnt fix it. Well I finally started correcting this tonight, I've got the engine set at 3 degrees down, and found that when I tried to change the rear pinion to 3 degrees UP, it made the driveshaft too long and bottoms out in the trans. I've seen somewhere that I can run the pinion DOWN at the same angle down as the engine, which allow the angles to cancel. It would save me from the driveshaft issue, but does this really work, or should I just get it over with and cut the driveshaft down?
Get the drive shaft shortend, and it will be ballenced as well! So, that will take care of that, I did that on my 51 shoe box and got rid of some vibes that I was not abel to trace....Roach!
Yup, you can go 3 down and cancel the angles, they have to be equal, either positve or negative, to cancel each other out.
If that little amount of angle change caused the drive shaft to bottom out, then it was too long to begin with and quite possibly a contributing factor.
Yes: I beat my brains out before I found out I could do this. Almost have to with a banjo rear end because the tire dictate it.
The angle of the engine and pinion are really not the issue. The real issue is the working angle of the U-joint. it should be a minimum of 0.5º to a amximum of 5º. Adjusting the angle of the engine/trans and the pinion is what allows you to achieve these working angles.
The comments on driveshaft length are right on. If tipping it up causes it to bottom out in the ******, guess what will happen when you get your foot in it. Even with gentle acceleration, the pinion snaps upward pretty sharp until it finds equilibrium. You'll be slamming it into the ****** with every shift......... Drive a pickup without a box on it for awhile and watch how much the pinion moves - I couldn't believe it! (This may be specific to Ford 9" rears - I suppose it depends which side of the ring gear the pinion mounts and/or which direction the teeth are cut)
Not really affected by the side of the ring gear or the angles - But rather Newton's third law of physics: For every action, there is an equal and opposite reaction. In this case teh action is the rotation of the wheels - if the leading edge of the drive wheel is rotating DOWN then the reaction (for the structure holding it) is UP. Front of tire goes DOWN - pinion goes UP. If you back up the car - the front of the tire goes Up andf the pinion then wants to go DOWN. That damn Newton was a sharp fella - he even knew about cars!!!
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