GM 12 bolt Pinion Depth

mycars51 · Apr 27, 2009

My 69 camaro has 12 bolt 4:56 rear end. One teeth was broken off the ring gear. I am presently replacing with Richmond gears 3:73. I took everthing apart and cleaned it, press in new bearing on the carrier and racers on the axle housing. I installed the bearing on the pinion and it's temporary in the housing without the crush coller. My choice of depth tool is 81655 - JEGS Ring & Pinion Set Up Tool Kit . The instruction are hard to understand, but got good idea from this guy at http://www.angelfire.com/theforce/5ohcpa/cpa5ohtech024.ht
My two questions are:
1- if you look at the head of the pinion as a clock and take measurements with the dial indicator placing the extension tip on end position 9 o'clock and then position 3 0'clock the reading are equal, but when placing in the 12 o'clock and 6 o'clock position the 6 0'clock readings are higher then 12.
The pinion rotation is fine. Pinion bearing, Pinion bore racers are all sitting flush.
2-Is the housing pinion bore setup in an angle?
.

prostreet6t9 · Apr 27, 2009

Do you Know what series carrier you have?
Did you reuse the original pinion shim?

cranky1 · Apr 27, 2009

I have an old Pro Parts setup tool and it doesn't look anything like that one but the last one I setup, I just used my depth mic to do it after I confirmed the bearing cap and fit was actually on the centerline. Anyways, my setup tool uses a magnetic target plate that just sticks to the pinion head and the indicator measures to it from centerline....and I use 'dummy' bearings to set the pinion and once that's done, then the permanent bearings go on. If you install the new bearing and have to make an adjustment, you may mess it up pressing it back off.

mycars51 · Apr 27, 2009

I wish I would had thought about that. I already press on the new bearing with the orginal shim. But what I am trying to find out, if it is normal to have these measurement. Top edge of pinion head .506, bottom is .513 the left side is .511 and the right side edge is .510. I didn't do the subtraction or addition yet to get the proper shim.
I am confuse, how could you have a pinion flat in its bore not measuring the same or at least close as the right and left measurements.
I have a carrier series 4

cranky1 · Apr 27, 2009

Does the middle of the pinion head have a raised face? Are you getting those numbers from the machined face where the teeth end? I use the middle of the gear head for my measurements. Sometimes they are machined smooth and sometimes they are not. I'll use my magnetic target plate if they are rough machined and subtract the thickness of it. Do you have the front installed and snug?

mycars51 · Apr 27, 2009

Thanks Cranky1 First problem is solved, I didn't have my tool bar mounted correctly as in the picture in the instruction and when said, you measure from centerline of pinion with your tool. I measure as close to the center of the pinion head and the numbers came out equal on all four corners. Now to the next step.
Thank you

cranky1 · Apr 28, 2009

Good deal. Meant to say front bearing installed. A buddy used to just try and do that without it and never got good numbers lol

mycars51 · Apr 29, 2009

From bearing is installed without the crush coller.
Now I having problems understanding instruction using my toolhttp://www.jegs.com/InstallationInstructions/500/555/555-81655.pdf
On step 4 it tells you to measure the carrier bore. I used the 2.3 extension and got 0.814 and I assume you subtract 2.3 from that number and get 1.486.

Step 5 measure the pinion head which is 0.504 and I subtraction the 3.3 extension and got 2.796. The Pinion is etched from Richmond gear for 2.830. And this is where I got confuse, the last sentence in step 5 said, record the measurements and add or subtract the offset?

My question is when do I subtract or add and to what number?
Do they mean add carrier bore to pinion distance 1.486 + 2.796 = 4.282
or subtract 1.486-2.796= 1.31

cranky1 · Apr 30, 2009

mycars51 said:
From bearing is installed without the crush coller.
Now I having problems understanding instruction using my toolhttp://www.jegs.com/InstallationInstructions/500/555/555-81655.pdf
On step 4 it tells you to measure the carrier bore. I used the 2.3 extension and got 0.814 and I assume you subtract 2.3 from that number and get 1.486.

Step 5 measure the pinion head which is 0.504 and I subtraction the 3.3 extension and got 2.796. The Pinion is etched from Richmond gear for 2.830. And this is where I got confuse, the last sentence in step 5 said, record the measurements and add or subtract the offset?

My question is when do I subtract or add and to what number?
Do they mean add carrier bore to pinion distance 1.486 + 2.796 = 4.282
or subtract 1.486-2.796= 1.31

If the pinion is etched with a depth measurement, don't worry about the thickness of the gear head. Mounting distance and pinion depth are two different ways to set the pinion. If the gear wasn't marked, you would have to use the mounting distance method but since the pinion is marked, you will use the pinion depth method which is the distance from the ring gear center line (or center of the carrier bearing bore) to the 'back' face of the pinion...the face that you are looking at from the back of the rear. 2.380 is what you need from that face to the center line of the bores. Hopefully, the bore center line was machined on center. They are usually very close but never perfect. That tool looks a bit odd to me. Mine sets up with the bearing caps and dummy blanks holds a round rod that the indicator mounts into. And I never saw a set of aftermarket gears that were etched using the mounting distance dimension. They have always use pinion depth. I also don't think you measured your carrier bore right because your bearings should be much bigger than 1.628 in diameter (1/2 of 1.628 is .814). That's pretty small bearing for a carrier.....

cranky1 · May 1, 2009

Did you get this together?

GM 12 bolt Pinion Depth

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