can you stack pinion angle shims?

I've got a flip kit/c notch & lift shackles in the rear. I had vibration on hard launches and from approx 55-60 mph. the guy that did my gears said my pinion angle was 8* up. I added 6* shims & the hard launch & 55-60mph vibrations went away, but I've got driveshaft vibration beginning at 75mph. I just blew up a 1piece aluminum driveshaft this past week at 90mph. right now, looking at the pinion angle, it's pretty much level with the ground.

So, I've got 6* shims right now, but need more angle. I can't find any shims more than 8*. If it's ok to stack them, I'm thinking about buying a set of 4* shims & adding them for a total of 10*, & going from there until I get it right.

 

The problem you run into with stacking is that the locator dowel may not extend into the second one enough to keep in in place.

I've seen people replace the dowel with a bolt. Hope this helps

 

Also be sure to check the angle of the front of the shaft too. They should be opposing and the difference between the 2 need to be -2 to -3*. So if your front is straight in line, the trans mount will need to be shimmed to get some angle there. The problem is not always just the rear setup, it has to be done as a whole to be done right.

 

The best thing to do is measure your existing angles, and work on both ends of the driveline. That said....

I don't like the idea of stacking shims(or blocks) ever. If you have a setup that absolutely requires more than one shim, try to use a shim(s) that can be bolted to the leaf spring pack with a new center bolt. At least that way, there's very little chance for anything to come loose.

If needed, center bolts with longer locating pins are available, as are shim/spacers that will extend the locating pin. Check with your local spring shop, or shop online for them.