Axle shims?

[Skandocious]

So my truck has had a vibration that happens when accelerating from a stop, for quite some time... The truck has a 4" suspension lift and a 2-piece driveshaft, and I made the problem A LOT better by shimming down my driveshaft support bearing to make my driveshaft a bit straighter

but the vibration is still there... I figured I might try to shim my rear axle and point the diff up more towards the t-case... Anybody have experience with this? How many degrees would I need for a 4" lift and where can I buy them? Couldn't find any on summit...

 

[surewhynot]

Most lift springs come with shims. Did you get springs or blocks? Most likely a 2 degree shim will suffice. Lemme look to see where you can get them.

 

[Skandocious]

The lift was accomplished through the use of a couple add-a-leafs. It was lifted by the previous owner. Still has stock blocks and the pinion points almost totally parallel with the ground.

 

[surewhynot]

Summit has them. http://store.summitracing.com/egnsearch.asp?N=115+-42166+-121900

I would try the 2* shims in the proper width for your springs.

 

[blacksnapon]

most generally, you want the driveshaft at no more than a 3 degree angle.

 

[mrfixit]

Will the 2degree shim increase the pinion angle sufficiently? He may need to have the axle mounts re-welded and even narrow the tranny mount for proper alignment.

 

[surewhynot]

You want equal but opposite angles at each end. So if your front joint is about 2 degrees down, your rear should be about 2 degrees up. With just 4 inches, 2 degree will be a good starting point. Vince is 100% correct, ideally you don't want any more than 3 degrees, but sometimes that is hard to achieve with a lifted truck.

 

[Skandocious]

Damn Tony I searched for pinion shims and it gave me the thin circular shims for shimming the actual PINION inside the diff (spacing it out). Thanks for the link.

What is the proper way to measure my driveshaft angle?

 

[surewhynot]

Will the 2degree shim increase the pinion angle sufficiently? He may need to have the axle mounts re-welded and even narrow the tranny mount for proper alignment.

I think it will be a good start because he isn't lifted too high.

 

[surewhynot]

What is the proper way to measure my driveshaft angle?

I use a protractor and a straight edge. There may be better ways, but that is the only way I have ever done.

 

[Skandocious]

Yeah Tom is all that really necessary for only 4 inches of lift? I'll go take a picture of my pinion angle, you'll see its not that hardcore...

 

[Blue Goose]

I was just getting ready to say protractor.

 

[mrfixit]

short of being absolutely sure the truck sits level on level ground, yep. I have heard of guys using laser levels, but that's an investment lol

 

[mrfixit]

Yeah Tom is all that really necessary for only 4 inches of lift? I'll go take a picture of my pinion angle, you'll see its not that hardcore...

Not if the shims handle it. You want the alignment to match what it was stock.
but sometimes the protracted length ot the shaft can do it too... It's designed to slide so far in, and you have it a bit further out now.

 

[surewhynot]

You want the alignment to match what it was stock.

That is what most people miss when they lift a truck. Everything was engineered to work a certain way and any deviation from that way can be a problem.

 

[Skandocious]

That is what most people miss when they lift a truck. Everything was engineered to work a certain way and any deviation from that way can be a problem.

Hence why I shimmed down my driveshaft

 

[surewhynot]

Exactly. It's nice to see you did it right, instead of just using washers like some people do.

 

[Fellro]

You can get an angle finder, basically, it is a weighted needle inside a marked housing. Harbor Freight has them for certain, not sure where else has them. I have mine from my fabrication days, very handy for setting powertrain angles..

 

[Brian_B]

I even have one of those laying around somewhere. I would not take my protractor out of my drafting kit and crawl under a truck. Picket brand is not a cheapie. LOL

 

[surewhynot]

Take your laptop out there and draw it up with cad.