Pinion setting plate

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Mbetti
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Pinion setting plate

Post by Mbetti » Fri May 26, 2023 6:08 pm

Anyone have of these to sell?
Pinion setting fixture.

Thanks,
Mike
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Rebel Walker
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Re: Pinion setting plate

Post by Rebel Walker » Sat May 27, 2023 1:49 am

Pretty EZ to make. Just measure up & waterjet.

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dpcd67
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Re: Pinion setting plate

Post by dpcd67 » Sat May 27, 2023 7:12 am

Ok, send me a drawing and I'll make some and sell them here. I have to make one 4x8 sheet of them though.
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Rebel Walker
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Re: Pinion setting plate

Post by Rebel Walker » Sun May 28, 2023 5:23 am

Pinion depth & bearing preload setting is the most important 1st adjustment in setting up a differential properly.

Not sure why this pinion depth always becomes attuned to rocket science, when it really isn't.

All one needs is a solid, not too thin plate, like even 3/8" plexiglass is fine. This can be done easily by waterjetting or even a jig saw & drill.

Drilled to suit the 4 bearing cap bolts & hole above the pinion, to measure pinion position using a depth micrometer, is all simple stuff.

Basic understanding of the + & - markings on the pinion, how to zero the micrometer, read & subtract the plates thickness from that reading, to get the correct pinion depth setting.

Can't remember the exact depth but 1.25" comes to mind - someone with more recent experience may want to chime in.

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OldGPW
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Re: Pinion setting plate

Post by OldGPW » Sun May 28, 2023 8:30 am

Buy yourself a good depth micrometer set (I use a Mitutoyo) with interchangeable length inserts. You need an absolutely FLAT surface to place over the bearing cap seats (and be sure that they are not deformed with any burrs that would throw off the accuracy of the reading). I keep random pieces of steel plate for this purpose. When measuring, you subtract the thickness of the plate your micrometer is sitting on. It's not the most precise way (precise would be measuring from the bearing bore, not the cap seats, but the proper gauges for that are almost non-existent), but it gets you into the ballpark; from there you check your backlash and patterns, etc. The manuals have the instructions.

You'll also need a good differential side bearing puller, or you'll increase the chances of damaging a bearing (a damaged bearing is a destroyed bearing).

Make sure you have several sets of the pinion shims (inner and outer) and the carrier shims on hand, so you don't have to be in the middle of it when you find out you're short on the shims you need.
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savmag
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Re: Pinion setting plate

Post by savmag » Mon May 29, 2023 12:19 am

Rebel Walker wrote:
Sun May 28, 2023 5:23 am
Pinion depth & bearing preload setting is the most important 1st adjustment in setting up a differential properly.

Not sure why this pinion depth always becomes attuned to rocket science, when it really isn't.

All one needs is a solid, not too thin plate, like even 3/8" plexiglass is fine. This can be done easily by waterjetting or even a jig saw & drill.

Drilled to suit the 4 bearing cap bolts & hole above the pinion, to measure pinion position using a depth micrometer, is all simple stuff.

Basic understanding of the + & - markings on the pinion, how to zero the micrometer, read & subtract the plates thickness from that reading, to get the correct pinion depth setting.

Can't remember the exact depth but 1.25" comes to mind - someone with more recent experience may want to chime in.
During my last rear axle rebuild a few months ago, I measured the distance of the centers of the 2 diagonal holes (left bottom and right top) of the bearing caps and I gave these to my local workshop. I asked them to construct for me a steel bar of exactly 0.5in thickness on a lathe. (a steel bar of any thickness can do but I recommend it to be steel or stst otherwise it may get bent).

I then installed the pinion bearing cap first without any shims and pinion and took the following measurements:

Total depth from the top of the bar to the face of the pinion: 2.766 - 0.5 bar thickness = 2.266. 2.266 - 2.25 (Pinion nominal depth) = 0.016. Pinion mark was +2 therefore, 0.016 - 0.002 = 0.014 total amount of shims to be added behind the pinion bearing cap.

I dare to say that the results were excellent. The contact tooth pattern, after setting up differential carrier bearing preload and backlash to 0.005in. was textbook correct. Unfortunately, I did not take any photos. The differential is silent.

TIP: It may be the case that the threads of the differential carrier bearing cap seats (where the bearing caps are bolted) are pulled a bit outwards due to unknown handling of previous mechanics, thus damaging the chamfer. In this case, you cannot take measurements using the plate because the surface will not be flat. As a solution, you could use a large drill bit, (a lot larger than the hole diameter) to re-chamfer the hole. You can check the image below (right side).

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Re: Pinion setting plate

Post by bazza1946 » Mon May 29, 2023 3:27 pm

Hi Rebel Walker,
The reason pinion setting seems so complicated is because of the factory setting gauge.It SEEMS overly complicated,but there IS a reason.
We all assume that the pinon bearing carrier is split EXACTLY at the center line, therefore, placing a plate on that surface and measuring down to the pinion is all you need to do.
BUT, with the manufacturing processes of the time, the machines' tolerances could not be held close enough to guarantee that the hole was split EXACTLY at the center (mind you, we are only talking about .001 - .005" here, but that is enough to throw things off when you are dealing with pinion depth of hypoid gears. So the factory boffins devised a gauge which had two precision circles,which sat in the bearing cradle half holes. Then they designed a connecting bar which sat EXACTLY at the center of the circles, to be a basis for all your depth measurements. Hence the complicated kit.
Now, the flat plate idea cannot be guaranteed to get the depth correct to exactly the real specs, (although your diff may have been machined exactly-we can't be sure) BUT, it seems to get us to a GOOD STARTING POINT, pretty close to right. From there, we can use the engineers blue test to FINE TUNE the pinion depth.
I, personally, not having the real gauge kit, have used the plate method, and it got me reasonably close to getting the correct wear pattern on the pinion. I did, however, have to add a shim or two after viewing the paint wear pattern test.

Fortunately, the TMs have a page of illustrations showing correct and incorrect wear patterns. Perhaps they anticipated people using other means of setting pinons, or expected some army mechanics to stuff up the use of the real gauge.
Cheers, Bazza

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Re: Pinion setting plate

Post by bazza1946 » Mon May 29, 2023 3:47 pm

An additional thought;
i have for some time, wondered how I could test how accurately my pinion bearing mounts were split, center line wise.
I came up with this idea, but I don't have the precision gauge to do it - namely, an internal measuring micrometer.
But here's my idea.
With the crown wheel removed, re install the bearing caps and tighten down to specs.
With the inside micrometer, measure the diameter of the hole in a horizontal plane, looking at the diff as it is installed.
Note the measurement to the nearest thousandth of an inch. Halve that distance and write it down
Remove the bearing caps and install your flat measuring plate. Measure the distance now. It should coincide with the result of halving the whole distance.
If not, (say, it's .002" more, then the center cut is .002"higher than it should be). Use that to compensate when using the plate.
Cheers, Bazza

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Re: Pinion setting plate

Post by JAB » Tue May 30, 2023 3:35 am

Great explanation Bazza, and good idea for compensating.
-Jeff

GR8GPN2U!!!

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