Pinion depth calculation clarification

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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JAB
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Re: Pinion depth calculation clarification

Post by JAB » Tue Aug 09, 2022 1:20 pm

Referring to my previoius post; I had some time to kill while paint was drying so I jumped ahead slightly in the project line. I won't actually be setting up the gear sets for a few months as I've got to repair the frame first. I made some stands to hold the differential but if you're just doing one or two you can do it on a work bench or, if you're young, in the vehicle. I've never tried it on a truck-lift, but that might work too.

I used blue chalk to highlight the factory indicators for the bearing cap orientation. On this particular differential the technician used a #5 stamp. The last one I did was a #2. Sometimes it's a letter instead of a number. What matters is that the digit is right-side up on one cap and a matching stamp is on the adjacent gasket surface. The other cap has the digit laying on its side, as is the matching stamp on the adjacent gasket surface. For the record, I found this one with both caps upside-down, and on the wrong side, proving that you can't trust the last guy that was in there.
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The spec for runout, either radial (similar to out of round) or lateral (side to side wobble) is 0.006". This one was at 0.003" on the radial runout but was barely in spec laterally.
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-Jeff

GR8GPN2U!!!

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savmag
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Re: Pinion depth calculation clarification

Post by savmag » Tue Aug 09, 2022 10:43 pm

Jeff,

Thanks for the clear photos.

One question for the bearing caps. If the star lock washers are consumed, would be a good idea to replace them with Nord-Lock washers or should I stick with new star washers? https://www.nord-lock.com/shop/washers/steel/nl1-2/

My only concern with Nord-Lock washers is that the bearing cap torque is set as per manual to 38-42 ft-lb which for the bolt size standard is quite low and it may not wedge and grip adequately.

Thanks,
Savvas

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JAB
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Re: Pinion depth calculation clarification

Post by JAB » Wed Aug 10, 2022 3:24 am

That’s a great question and probably open to personal discretion. I use similar new internal toothed lock washers with Permatex #2 on the threads. The Permatex serves two purposes; since the threaded holes are through holes, it serves to seal them, but it also serves as a form of removable lok-tite that has withstood the test of time. The lock washers become a secondary and redundant method of bolt retention. Upgrading to a “better” locking washer may not be better due to the lower torque settings used in the cast-type differential case, preventing them from functioning as designed. I’m a traditionalist and with these antiques I tend to not overthink or upgrade much, if anything. I no longer use RTV silicone or Teflon tape on anything antique. It’s just a personal choice.
-Jeff

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savmag
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Re: Pinion depth calculation clarification

Post by savmag » Sat Sep 24, 2022 7:14 am

Hello to all,

Following my initial post, I started the rebuild of the rear differential with the help of a local experienced mechanic. There are 2 initial issues that I would like to address to you before proceeding to the gear marking compound pattern check and your comments are always valuable:

Issue #1

After measuring the shim thickness needed on the pinion gear using the centerline method, the new shim pack thickness is 0.014 in. The old shim pack thickness (with the old gear set) was 0.026 in. New pinion +2, old pinion +10.

I find peculiar such a difference, however the new gearset is a Spicer with manufacturing date 1974 and the pinion does not have a pronounced shoulder like the older one. The bearing sits on the gear instead on the shoulder like older pinions. I find it very possible that the new type of gear set is manufactured differently than the original gear set thus requiring a different amount of shims.

Issue #2

There is an other manufacturing difference between the old and new pinion. The new pinion is manufactured in such a way that the sleeve which goes between the pinion and preload bearing is too short and sits just below the edge of the "step". I have attached a sample photo below from the Kaiser website that it is quite clear.
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The mechanic's suggestion is to remove the sleeve completely and install the required amount of shims directly on the "step" since it is right angled and can withstand the pressure of the nut. The step essentially works as an integrated sleeve in this case.

Thanks for all your suggestions and I will revert with any further issues that might arise.

Brgds
Savvas

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Re: Pinion depth calculation clarification

Post by JAB » Sat Sep 24, 2022 8:07 am

I believe that the advice your mechanic freind gave you correct; due to the manufacturing differences over time, the sleeve/spacer became obsolete. Why have an extra part that can be eliminated with a simple change in the machinging process? I'm not aware of any other Dana-Spicer pinions that use that sleeve/spacer other than the WWII jeeps and some early CJ's.

I don't have an answer for the 0.004 difference in your math unless one of the signs was a + and the other a - sign, then the math works perfectly. And don't forget, this is just a starting point, the pattern will determine success (but I admit that the closer I've been to my measured postion the better the patterns have been).

Don't forget to install the new inner seals now so that you don't have to pull it all apart later when you realize that you forgot them!

I'm just starting on those four differentials I mentioned earlier and discovered that my factory tool fixture is no longer giving me reliable or repeatable results. It must be bent (aluminum) from improper storage (too much stuff cramed in the box putting pressure on it for years?). As a result I'm re-machining my model 44 differential flat plate to fit the model 23/25 as well. It's a bit tricky but it's looking good so far. I'm also considering modifying it to enable me to do the measurements directly without doing any math. I'll post a picture later if I decide to do that as it's too difficult to explain. I figure the time spent now will pay off in frustration later.

You can see the aluminum (hook-shaped) tool on the floor. It hangs from the pinion center-drilled holes and holds a fixture that's calibrated to measure the pinion depth based off of the bearing bore. I prefer the flat plate method, which is why I'm finally making my model 44 plate a "universal" plate. My model 60 plate is way too big, but this one should work. Getting a good starting point saves time and frustration later. In case you're curious, what you're seeing is the removal of the inner pinion race (to adjust the shim pack) with the post-war Willys factory tools.
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All my shop-built model 60 bearing puller/installers were stored on top of it, possibly causing the distortion.
IMG_0548.jpg
-Jeff

GR8GPN2U!!!

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