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Old 08-04-2008, 01:20 PM   #1
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How to measure backlash with a dial indicator?

I have to re shim my carrier. I bought a dial indicator and some shims. How do you hook up a dial indicator to get the correct measurement? What's the best process for getting the correct backlash?
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Old 08-04-2008, 01:36 PM   #2
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Re: How to measure backlash with a dial indicator?

Attach the magnetic base somewhere so the dial indicator can sit on a ring gear tooth. Hold the pinion so it doesn't move and gently move the ring gear back and forth just enough to measure the backlash. If you move the pinion by moving the ring gear, you're not measuring backlash.

On a GM differential, backlash is adjusted by changing the shim thicknesses but the bearings also need preload so a case spreader is normally used to get the shims in and out.
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Old 08-04-2008, 04:28 PM   #3
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Re: How to measure backlash with a dial indicator?

Seeing that I don't have a case spreader, am I going to be a able to preload the bearings?

So if I get this right, I have to measure backlash and get it within specs. Then I have to add .004 thickness to each of the sides which will require some sort of spreader to get the shims in.

When you say, "sit on a ring gear tooth", what exactly do you mean? The edge of the tooth? What is the angle the indicator needs to be at?
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Old 08-05-2008, 01:21 AM   #4
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Re: How to measure backlash with a dial indicator?

you should set the indicator tangent to the ring gear. so, the gear being in the vehicle and looking at it from the rear of the car, the indicator being mounted in a vertical position. the middle to outside edge of the tooth is where the end of the indicator needs to be when measuring.
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Old 08-06-2008, 06:16 AM   #5
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Re: How to measure backlash with a dial indicator?

Here's a picture of how I had mine setup. A case spreader is absolutely not necessary. If you have to use a hammer and a flathead screwdriver, or even better, a brass drift, to be able to tap the shims in on each side, then it will be tight enough to preload the carrier bearings properly. You want your backlash to be .006"-.010". That's the proper range. Once you get the backlash set right, you might need to add about a .002" thick shim to each side to get the preload tight. Just make sure to use the same thickness on both sides so you don't change the backlash.
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Old 08-06-2008, 10:11 AM   #6
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Re: How to measure backlash with a dial indicator?

Thanks for the advice and the picture. I think I can do this now!

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