Setting pinion depth -
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post #1 of 5 Old 06-13-2013, 01:42 PM Thread Starter
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2000 TJ Wrangler 
Join Date: Jul 2011
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Setting pinion depth

I am rebuilding the rear end of the old ford (9.75LS 3.55 gears)pickup. The head/inner pinion bearing let loose, no gear oil, where did it go? Short story, I need a way to calculate the pinion depth.
I am installing a replacement OEM 3.55 Gear set without any checking distance markings.

The original shims were destroyed when the inner pinion bearing failed. The bearing itself was unrecognizable except for the outer race. Normally I would simply hone the inner pinion bearing's inner race until the bearing could be slip fit on the pinion shaft and go from there. See Pics.
I fear that if I have to install and remove the inner pinion bearing several times to accommodate shim addition/deletion that it would be ruined

Normally will hone the inside race of the Pinion head bearing to a slip fit only for setup of the new Pinion's depth. It would then be replaced by the new bearing and race along with the tail bearing, carrier bearings, wheel bearings, and seals.

However not this time. Pinion depth gauges are rather expensive and complicated even for most pros.

Ratech make a very accurate and affordable Pinion Setting Tool at around $30.00 but not for the 9.75.

Randy's ring and pinion Sells Set up bearings that are prehoned, nonreturnable and also a bit pricey.

My math and machinist skills are not what they used to be. Just cant seem to work out the specs/measurements into something useable. My hard drive is too dependent on the one in the laptop. L O L

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post #2 of 5 Old 06-13-2013, 04:02 PM
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If you don't know the basic setup distance (from the back side of the pinion head to the center of the carrier bearings), there isn't any tool that is going to help you. It won't help you to measure the pinion depth, if you don't know what it's supposed to be. The only way to do this is trial-and error with gear marking compound.

Make yourself a set-up bearing, install the pinion and ring gear, and read the pattern. Disassemble, adjust the pinon depth shims, and try it again. Keep adjusting until the pinion depth is close. Then adjust the backlash with the carrier bearings. Once you that where you like it, you will most likely need to readjust the pinion depth. Back and forth, in and out, over and over.

Remember, adjust pinon depth first, then backlash second. It takes a while...

The road goes on forever, the party never ends....
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post #3 of 5 Old 06-14-2013, 10:08 AM Thread Starter
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Thanks for the reply. I was looking for a short cut or at least a starting piont. The local shop I where I picked up the gears and bearing kit recommended 23 thousands. Thats where I will start and follow your advice from there.
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post #4 of 5 Old 06-17-2013, 06:36 AM
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Is there anything left of the old shims? Even a tiny piece can give you something to mike for a starting point. Otherwise, toss a .020 in there and go at it.
Ge sure you have a good bearing puller or set up bearings or you will wind up destroying your new ones.
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post #5 of 5 Old 06-18-2013, 08:37 AM Thread Starter
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Thanks for your thoughts. Hope to get things done today. Will let you know.
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differential , pinion bearing , pinion depth

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