Home-made laser diff alignment tools

[Guest bluex_v1]

http://www15.brinkster.com/5o260z/difflaser.htm

check it out, tell me what you think. I still have some work to do before I actually put them to use, but i think they would work fine. If people think they are cool, maybe we can do something like the spindle pin puller loaner program once I get my driveshaft done...they still only cost me about $40 to put together though.

Tell me whether or not the directions make enough sense, etc too.

[EvilRufusKay]

Nice setup!! Seems like a great idea. I thought the instructions were written very clearly as well. Have you used it yet or have you just put them together for now?

 

Rufus

[Chaparral2f]

I used a laser level to align the drivetrain in my x31. First I had an empty 350th case that I used to get all the clearances under the car. I bought a cheap laser level from harbor frieght, and bolted it to a right angle bracket. Then I bolted the bracket to one of the bolts that would normally hold the tailshaft housing on the tranny so the level was centered where the shaft would be. I used the level instead of a pointer because it has a lens that shoots a straight line, and can be turned from horizontal to vertical. I figured that when both lines went through the center of the diff pinion shaft the driveline was straight.

 

I like your design it is a lot simpler than what I did. Not to mention that it doesn't need an empty trany case.

[Guest bluex_v1]

Have you used it yet or have you just put them together for now?

I have not used them other than fitting them on the lose diff and trans. I still need to finish up my suspension and get the front of the car on the ground again before I put the engine back in...maybe in a week or two.

 

I figured that when both lines went through the center of the diff pinion shaft the driveline was straight.

Unless I'm not visualizing something right, what you have described would not actually account for the angle between the centerline of the transmission and the driveshaft being equal but opposite of the angle between the driveshaft and the diff...unless you had the perfect set up where the transmission and diff center lines ended up on the same exact axis, as viewed from the side and from above. In other words, theoretically, your diff could have been sitting low but pointing up at a 45* angle and the laser still could be centered on the input of the diff. I believe you would need to do the same thing on the diff side to make sure your crosshairs ended up pegging the center of the trans output shaft.

hope that makes sense...I do need sleep.

Having the crosshair laser setup would be neat. I think i have the same level as you used in fact, but I couldn't think of an easy way to work with it.

[Pop N Wood]

Hey, I posted that exact same idea some time ago!

 

http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=24120&highlight=laser

 

Great idea! Good to see someone actually implemented it!

 

To simplify things slightly, you can go to a gun store and by laser pointers that are built into a pistol cartridge. They are used for boresighting gun optics. Nice thing about those is they have a flat base and should be already calibrated (i.e perpendicular). don't know what they cost, but my guess is your approach is cheaper.

[A. G. Olphart]

Neat idea, and put forth clearly enough to follow. Please post your experiences using these... I'm wondering about the fog/smoke generation needed to actually see the laser beams.

[labrat]

As for fog to see the beam, Right-Guard or any other aerosol works great. Right Guard has a floating, powdery texture to it and illuminates lasers very well.

[Guest bluex_v1]

Posting up my experiences using this:

In practice, it became too much of a pain in to accurately shim the socket against the magnet face to get a trued perpendicular beam. The lense assembly inside the laser itself was off by a couple degrees, so by the time it was properly shimmed, the beam may have been detectibly off-center. So, I decided to adhere to the KISS philosophy. I found some 1" circular magnets at homedepot for a couple bucks and just stuck the socket on one side of a stacked pair of them. This would cut assembly cost and time in half or more.

I ended up just doing kind of what 'Pop N Wood' suggested in the thread he linked to above. I used just the one magnet laser at a time on the transmission, and then on the diff. I cut out about a 6"x4" piece of cardboard, then cut about a 2" diameter hole in one end of it (actually more like an octagon). I taped a piece of paper over the cardboard and placed the cardboard/paper over the face of the diff, so that the input shaft stuck through the hole in the cardboard and pressed up against the paper. I could then take a pencil (or crayon) and rub the edges of the input shaft into the paper to get a nice circle. Then with the transmission in neutral, the output shaft can be rotated and the circular path of the laser on the paper can be traced, marked about every 10 degrees with a felt pen. Using a torpedo level, also mark a vertical line on the paper to differentiate horizontal vs vertical angles.

Using a compass or calipers, the center of the laser's circle and the center of the traced shaft's circle can be found. You can then measure the distance between the two circle centers in each plane, and then the distance between U joint centers. Take the difference between each circle in one plane and divide it by the distance between the ujoint centers. Find a calculator and get the sin^-1 of this value (that's sin to the negative first power, or I it might also be called inverse sin. Also, make sure the calculator is using degrees and not radians) this will give you the angle in that plane. Repeat for distance between circle centers in the other plane. Repeat the entire process for the differential angles.

I found I could very precisely determine my angles to a tenth of a degree.

I'll be updating my page with some pics of this too.