Ok guys, I measured the angle on my differential pinion today. I'm trying to get rid of that shimmy I've had since I put the shackle on my standard cab long bed (1 piece driveshaft). It's between 5 and 6 degrees up from horizontal (see pic). I forgot to measure the axle to see what it is, but it looks like it's less. After taking some measurements it looks like it's ~3.75 degrees. I'll verify that with a tool to make sure, but I'm fairly certain about that


Here's my question, with the 1.5" drop (2" advertised) is 6 degrees bad? It would seem to me that the pinion angle should be less than the driveshaft when sitting still? Anyone know the stock spec on that angle, I can't find it in anywhere in my Haynes manual. I have tried the 2 degree shim and it didn't solve my problem. I'm thinking a 4 or 6 now, but I would like your guys thoughts on it. I'm positive I was on flat ground, but knowing everyone on the board (including myself) I know the question bound to be raised is "how do you know you were sitting on flat ground to begin with?" When I measure the axle the next time, I'll make sure to measure the ground too.

All this being said, I'd like to try and find out what the stock spec is if anyone knows (or can measure their stocker). Just seems like you would want that pinion a little shallower, but that's just based on my gut feel. If I went with a 4 degree shim I could be ~2 degrees less than the driveshaft. Do I need to go to the 6?

Thanks ahead of time guys,
Andrew

 

Where did you take your pinion angle measurements from?
You will need to take the measurements between the driveshaft angle and the front nose of the diff angle. Then subtract them (I think) and that will tell you what * shim you will need.
You need 0 to -1 degrees. At least that's what one member here has stated.

Jim

 

Also, it looks to be that your shims will need to be place in with the fat side facing the engine.

Jim

 

http://www.rosslertrans.com/Tips/Pinon.htm

 

measured the pinion angle both on the flatt on that diff housing, and on the actual pinion "yolk" that attached to the driveshaft, both read 5-6. didn't measure the trans though. Looks like that needs to be measured too. Guess I just assumed that was 0.

 

The rule of thumb that I was told is that for every inch you lower the vehicle the shimm should be the same. For instance I lowered my truck 6' and used a 6 degree shimm and it rides perfect with no shakes. So if you did a 2' drop I would use and or try the 2 degree shimm

 

which way do you have your shims installed?

What are the suspension specs now? dropped? shackles? hangers? leafs? I think if you installed your shims incorrectly, which looks like the case, the angle would be about where it is now, which looks like the case If you flip the 2* shims around(depending on how they are currently installed), I think your pinion angle will get closer to 0 - this is my guess, no offense.


BTW, refer to https://www.performancetrucks.net/fo...d.php?t=373595 for proper installation of shims.

 

The thick endgoes towards the back of the truck. I will check mine again for you later today but I am sure the thick is towards the rear so that wen you tighten the U-bolts it actually angles the rear downward to give you the proper angle.

 

Ok, 2" lowering shackle, hotchkis sways front and rear. That's all suspension wise that I had on when I measured it. I put 2 degree shims on a couple weeks ago (thick end forward) and it didn't make the shimmy go away, so I took em back out.

If you put the thick end towards the back, it will actually pitch your pinion higher into the air. Think about stacking two bricks on eachother. the top brick is the leaf and is always at 0 degrees, the bottom brick is the axle/diff/pinion. If you put a wedge fat end forward(left), the bottom brick slopes down from right to left, which is what you want it to do. If you put the far and to the back (right), it pitches the brick so that is slopes down from left to right. Hopefully taht made sense.

 

I could care less about pinion angle specifications(no offense), your truck didn't shake when it was stock - so if you put drop shackles on, which ultimately rotate the differential(as seen below), why install shims to rotate it FURTHER in the same direction?!?!?! I'm no expert, but I'm not drop shackle stupid either.

Here's the pic from the other thread:


are you disputing this theory?