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Can anyone shed some light on how they got their drivetrain to be exactly the angle they needed after an engine swap?
I'm imagining a tool made of an old slip yoke to hold somethin like a bore laser for a rifle... Something made of stuff around the house and out of the junkyard that could be very precise in aligning the drivetrain.
Reason I am asking is because I am getting some drivetrain vibration at higher speeds and the guy that shortened my fbody aluminum driveshaft has a pretty good rep with the high hp drag racers around town. So i'm thinking it's either my drivetrain is a bit out of alignment (after I did my own engine swap and didnt align it perfectly), OR, my r200 nissan rear diff is wallowing out from being old and of nissan quality (regular r200 problems with 400+hp). OR, my driveshaft bolts wont stay tight (which keeps happening, despite the different bolts i keep trying), but I would think that is a byproduct of a misaligned drivetrain..
What I did on mine was get a angle finder at your local builders store . Remove the drive shaft and measure the pinion angle ( lets just say 3* up ) . Then measure the trans shaft ( lets just say 5* down ) . The rears are harder to move unless you have adjustable bars . So move the trans up 2* to match the rear pinion angle . What you are trying to do is have the trans drive line parallel to the pinion angle so the working angle are the same . Mine worked out pretty good doing it like this .
The up and down alignment is pretty simple, you only need an angle finder.
The yaw alignment I:
1) used string and plumb bobs to drop locations for the crankshaft and trans output shaft down to the concrete floor
2) marked a straight line from trans to crank with a sharpie
3) used a string taped to the floor to extend that straight line all the way back to the differential and drew another straight line with the sharpie
4) used a builders square off the differential flange to drop a straight line parallel to the diff flange on the concrete floor, again sharpie straight line which crossed the engine/trans center line
5) used the builders square to get a straight line perpendicular to the axle flange line, drew with sharpie on floor
6) measured the rise and run between the axle flange perpendicular line and the engine/trans center line and calculated the angle with trig
7) from there you can figure out how much to swing the engine/trans in yaw to make the centers line up, and re-check after
For the first couple times I did this I put down strips of blue masking tape where I drew with the marker, so I did not have several iterations of sharpie drawn on the concrete floor simultaneously.
I used a digital angle finder used to set up table saws. Cost me $40 Canadian, so will be about $20 us.. Its about 2in x 2in square and is magnetic. Use front of the LS head as it is 90deg to the crank, INSTSLLED driveahaft angle, and rear diff pinion angle to work the front and rear joint angles.
Like the others said you want them equal while operating. I allowed 0.2deg for rear axle wrap under load on mine (3rd gen fbody with a torque arm).
I had to raise the back of my trans and then adjust the axle pinion angle to get close to 2.5deg. You want to have the angles under 3deg.
Last edited by 6speediroc; May 10, 2017 at 09:11 AM.
Might work well if one glued a magnet to the mounting pedestal. It could be stuck directly onto the faces of the trans output shaft and pinion flange. The long projected laser line would make measuring relative angle simple. If you had two units, you could put one on trans and one on diff, and line the yaw centers up on the fly by taking linear measurements from line to line. If two linear separation measurements along the two laser lines (measured perpendicular to one of the lines) are the same, as measured 24" apart (or other random long linear distance), then you are parallel. The anglualr out of position measurement would then just be a rise/run arctan calculation.
One would have to do some calibration effort in setup of the magnet relative to the laser pointer base to make sure each of the two laser lines are perpendicular to the respective mounting flanges though. Not impossible, and once done, it's done.
Yeah, use two of them and if the lines are the same distance apart everywhere your alignment is perfect. I held a piece of notebook paper up, the lasers go right through it, and counted lines separating them. Calibrated the laser tools by spinning them on a drill press table and shimming until it scribes a single point on the ceiling.
This guy claims a shotgun boresight tool is already perfectly aligned, no need to calibrate
thanks for all the insight yall,
the magnetized laser pointer trick looks cheap and extremely effective, i think i'm gonna go that route first so i know i'm spot on and i'll just use some ol trig math to figure out my angles and all.
huge help.
i'll check my driveline angle first since thats probably gonna be the cheapest and most likely to be out of spec, then go from there.
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Drivetrain alignment after engine swap 
