Need help with something. I have done a complete drivetrain swap on my 54 plymouth. New engine and trans (318/904 combo) and a new differential. I have 3" blocks on the rear end so my car is LOW in the back. I haven't tacked the axle to the sping pads yet and i'm wondering how I set my pinion angle when my car is too low to crawl underneath it when its on the ground (ride height). I'm sure the angle will change if I jack the car up. I see cars on here dropped low all the time. This might be a stupid question and I'm willing to take the blocks off the back if that's what it takes. I just really like the tail dragger look of the car as it sits now. what am I missing?
Get the car up in the air with the jack stands, wood blocks, etc., placed underneath the suspension, or under the tires if you have some big chunks of wood (RR Ties).
Thanks for the reply. So basically just jack up the car under the differential and under the bottom control arms in order to get it at "ride height" in the air? How exact does this have to be? I know that the angle will change slightly under normal driving conditions (speedbumps, potholes, etc.) I had thought about doing this but didn't know if I could get the height on everything even. does it matter?
from what I understand, if the trans is 5 degrees down at the back, you want the diff 5 degrees up....if you were to draw a straight line through the motor and trans all the way back to the diff, you want the diff line parallel to that. http://www.carcraft.com/howto/91758/index.html look at the bottom picture on the left side.....
study here http://www.vibratesoftware.com/html_help/html/Diagnosis/Propshaft/Propshaft_Angles.htm#Measure
That's right. There should be a 3 degree difference between the diff angle and the driveshaft angle. You don't even have to have the front end off the ground. As long as you have jackstands or floorjack under the rearend. You're just checking the diff to driveshaft angles.
I think his question was how to get the car up in the air without dropping the suspension, thereby changing the angle needed at ride height. And no 4door, do not jack up just one end. You can't accurately determine your proper pinion angle when only one end is up in the air. Get a set of 4 floor jacks and put one under each end of the axle in back and suspension in front (better yet is to block it up on all tires, but be careful). Be sure the wheels are all the same distance off the ground and also be sure the suspension is at resting height. I also make sure I take into acct. the angle of the floor the car is sitting on (garages have a slope to them to drain water). Then go set your pinion angles and tack in the perches/blocks.
more than likely you will be using an angle finder like this To get an acuarate measurment with a tool like this the surfaces need to be as if the car was on level ground and at ride height. One possible way to set the car up is, as mentioned with 4 jack stands under the suspention so that the suspention is holding up the car on all 4 corners. And few stands under the frame for safety since you will be moving the rear end around. Place a staight edge, a straight 2x4 will do nicely on the bottom of the tires and make sure that plane is level front to back and side to side. There have been several links posted as to the pinion angle science and process and they are very well written.
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