question about lowering blocks & pinion angle

[a.d._510_n_ok]

if you use a 2" inch or less block is pinion angle altered so much as to necessitate shims?

[Dawa]

i think that the major consensus will be that for 2" blocks, youre good.

[datzenmike]

If this is for a goon you should put '80 HL510 goon' in your profile.

 

I used some 2" lowering blocks on my 710 goon which is pretty much the same thing as an A10 goon. It vibrated. More of a loud hum actually. It wasn't there before and was after. I placed a straight edge against the trans output and measured the angle from it to the driveshaft. I then did the same at the differential flange. Angle out must equal angle in in order for the drive shaft to cancel out the vibration.

 

I couldn't change the front U joint angle. But I could rotate the rear axle assy to tilt the fifferential uo or down to increase/decrease the rear U joint angle. As it turns to bring the two angles closer together the diff needed to be tilted down at the front. I had a 3" washer that was about 1/8" thick. I cut in half so I had two half moons. Loosened the U bolts and slipped it between the lowering block and the leaf spring on the rear side of the axle and torqued them down again. This turned out to make the angles so close that I couldn't measure the difference. Hum totally gone.

 

If you have ever held a drive shaft and turned it while holding the front spline ahead of the U joint you will know that it does not turn smoothly. In fact it tends to rotate in a jerking motion, more so as the angle increases. This is because the U joint is actually speeding up and slowing down because it isn't turning through a circle but an ellipse. (oval) Because the drive shaft is forced to turn evenly by the weight of the motor and the forward motion of the vehicle the vibration is passed into the body. Two U joints are arranged so that as one speeds up the other is slowing down and the two cancel... but only if the angles are also even.

 

 

Any unequal U joint angles will vibrate. 2" may not be enough drop to alter them but if it does this is how to bring it back.

[a.d._510_n_ok]

dawa, mike - thanks! I'm trying to do the least damage possible, ya know?