[waltman]

I have had a vibration problem with my truck since I bought it. I always thought it was my tires out of balance and later, a bent rim. Well after a lot of screwing around I determined it was my rear end (yoke) not in line with my drive shaft. It was only out by 2 1/2* plus a C hair. It doesn't sound like much, but apparently it is enough to cause a vibration. First thing you do is determine if your yoke is not in line with your drive shaft.


I used an angle finder, some people eye ball it, or you could be inventive and use a carpenter square with a piece of string and a weight on the end of the string.

For more accuracy remove the drive shaft from the yoke and place your angle finder directly onto the yoke. In this case I had checked it at an earlier date and established that the rib on my pumpkin was square off the yoke.

Next, or first, doesn't matter place your angle finder on your drive shaft.

So now you know what size shim to buy, go buy it and then raise your vehicle and place jack stands under your rear dif. Remove the wheels.
This is the shim I will be installing.

I find the best way to go about this is by doing one side at a time. If you remove the u-bolts from both sides you may have a problem lining everything up later. I ended up using a come-along last time.
What I did here was get some blocks of wood and put my hydraulic jack on it in order to raise the springs enough to remove the stock block.
NOTE: i DID NOT FULLY REMOVE THE NUTS FROM THE U-BOLTS BECAUSE SOMETIMES PUTTING THE BOLTS BACK ON CAN BE A HEADACHE OR SOMETIMES IT JUST WONT HAPPEN. SO DON'T REMOVE THEM IF YOU DON'T HAVE TO.

This is my factory block

This is the block with the shim on it. Notice the, for lack of a better word, nipple is barely beyond the shim. This could cause some problems, especially if you do any off roading and any serious articulation. Basically it could come apart on you. This of course is not something you want to happen no matter where you are driving. I have a piece of 5/8" round bar to the left, which I will be using to remedy this problem.

First thing you do now, is center punch the center of this nipple and then drill a pilot hole followed by a 5/8" hole. I wanted to drill a hole 1/64 smaller than 5/8" and then I was going to put the 5/8" round bar in the freezer and heat up the block so that it would have been more permanent when I put it together, but I didn't have a smaller drill, so never mind, the 5/8" drill worked fine.

I ended up cutting the 5/8" round bar to 1 1/8" long. Here it is with the round bar in the hole and the shim on top. You can clearly see this is going to work out better.

So now installation is in reverse order of how you removed it. Here it is back together with the shim in place.

Whatever you do, when you drill the pilot hole, don't break the drill bit, like I did on the second one. :banghead :banghead

Once you have completed the other side, re torque your u-bolts to 100 foot lbs. and don't forget to re-torque them in a few hundred miles. I'm not sure how many miles exactly, maybe someone could post it.

Now while you are here at the rear end, you may as well check your fluid level. First locate the plug.

Remove it, using a 3/8" drive ratchet.

Top it up if needed.

May as well grease your u-joints while you are here too. When you are finished go on to the power drinking.

So there you go, I hope this makes sense and will help anyone who is thinking of installing a shim.

*NOTE: I HAD THESE U-BOLTS MADE UP FOR ME A FEW WEEKS AGO. IF YOU DON'T KNOW WHEN YOUR U-BOLTS WERE INSTALLED, IT IS RECOMMENDED THAT YOU INSTALL NEW ONES.

 

[Agily00]

Where did you get the shims?

 

[DcSkater602]

they are 2* aluminums... maybe 4*

i have 2* shims im returning unless you want them... they are new

edit: you actually want more angle than that... ie: the pinion should point down past the driveshaft...not straight... when the pinion points above the driveshaft u egt a vibration... when it is dead striaght it will twist upwards on acceleration and still cause a vib...the fix...anti wrap bar

dc

 

[Bronco Dan]

Good, post.

Using the same approach with finding the angles, you can cut off the spring perches, turn your axle up according to the degree you need it to be at, then reweld some new perches back on. make sure you take note of the degree that the perches sat before you cut them off. Example, if you need to move the dif up 2%, and if you get rid of the shims, the add the shim degree plus the 2% you need and move the perches forward accordingly when you place them for welding.

This is most desired with rock crawling as you can put in a piece of plate steel between the springs and the perches with o degree's-why-the stock shims can blow up, push out, etc..under extreme twisting and flexing. A piece of place steel can be bought in sizes you want and lengths you may desire.

Getting new U-bolts that are thicker than the stock ones is also recomended if you are doing some heavy 4x'ing.

Good post, pics, and problem solving Waltman!

 

[kf4amu]

Bronco Dan I wish I read your post a year ago before guestimating where my new perches needed to be welded. Turned out I twisted the pinion too far up, now my shims will need to be installed to point the pinion back DOWN.

 

[waltman]

Where did you get the shims?

I got the 2* shims from a local 4x4 fab shop. The shims didn't make much difference though, I didn't think they would, but I was running out of ideas.

Man, I did this write up over a year ago.

 

[USMC_Fords]

Sorry to bring up a 4 year old thread. But it's better than starting a new one. I installed my 6* shims yesterday, and had the same problem with the nipple. Does anyone know for sure if the 5/8" round bar will work on all Broncos? I'm doing this tomorrow hopefully, and don't want to have the truck apart just to find out I got the wrong size.

 

[waltman]

I don't see why not. You'll find out for sure when you take it apart.

Just to update: I was at the end of my rope when trying to find the source of the vibration when I did this. Before this I spent a fair bit of time and money to fix the problem to no avail and since doing this many many more hours and more money still with no luck. I recently bought all new tires and the problem improved quite a bit but is still there. I've totally run out of ideas, but I don't do that much driving over 110 KPH, so I don't care anymore.

 

[USMC_Fords]

Oh, mine is lifted 6" so the vibration was there below 15 mph and when slowing down to that speed. I also had a shudder when slowing down from high speeds. This fixed both of those issues.

 

[96broncoman]

I'm using the ORD zero rate block in the rear, and I was curious if I could bolt the shim in between the leaf springs and block, or bolt it to the bottom of the block, so that the stud still sticks through the block and shim. I can clearify that question if it reads too difficult.

 

[waltman]

As long as that pin sticks through the shim enough to be effective then it should be ok.

 

[96broncoman]

so should i just bolt it between the leaf spring and zero rate, or should i bolt it in on the bottom of the zero rate?? I was thinkin i would put it in between the leaf and block.