lowering and pinion shims

[Fordf100++]

Hello. I recently lowered my 1970 f100 SWB using 2" lowering shackles and hangers. About a 4" drop. I made a big mistake not measuring the pinion angle prior to doing this work, so now I am stuck trying to fix it without knowing what it was at before. I had a mechanic measure the pinion angle and he told that if I put shims in, it would be fine. He told me to use 3*. I installed the shims, but it just doesn't seem right. (Slight bumping or as I go in reverse out of driveway and slight vibration when driving). So I bought a measuring tool at harbor freight to measure myself, but I am unsure if I am doing this correctly. I attached pics. I am getting a measurement on the driveshaft of 6* and measurement of 8* on the rearend. First of all, I need to know if I am measuring this correctly? Also, if so, are these numbers acceptable? Also, I was told by the same mechanic that I may need to shorten the driveshaft due to lowering the truck? I attached a photo of the drive shaft input to trans. Does that look too tight? Thanks for your help! I definitely could not do this without it!

[eggman918]

Look at this PDF from Dana/Spicer
http://www2.dana.com/pdf/DSIG-3311.pdf

[Fordf100++]

Thanks for the post. From what I can tell from the article, is that you should be within 3*. Is this correct?

[eggman918]

Yes...but the closer the better/smother it will run and the longer it will last.

[Fordf100++]

From my pics can you tell if I am measuring accurately?

[eggman918]

I don't think so,you want to use the machined face of the yoke on both the output shaft and the pinion.since they are u bolt yokes you will need to pull the drive shaft and turn the yokes so that they are horizontal and place your protractor across the face that the holes for the U bolt are drilled it should have been machined square to the center line on the shaft so that will give you a good reading.

[eggman918]

also remember that one points down and one points up,but the object is to get them on the same plane.