Packard Forum Index » V-8 (1955-56)

Having picked up some copies of the factory drawings, I'm able to give some data:

Shaft dia was .4930 to .4935
Bore dia was .4950 to .4960
Note that this applies only to the driving shaft. The driven gear was on a dowel pin, 440601, which was a press fit into another .495–.496 hole.

You will note that this is a 1.5 to 3 thou drive shaft tolerance from the factory; yet no allowance past 3 was given in the service checks.

The two gears were identical except for the obvious differences and bore dia.

The gears when mounted in the pump have an end clearance per the factory drawings of 2 to 6 thou, yet strangely the service manual gives no more than 3 thou as acceptable. I have a 1953 and 1956 oil pump body drawing and this was not changed between them. My gear drawing is from 1953. Though both the "1953" drawings were revised through 1955 with no change in this regard. In addition I have another oil pump assembly drawing from 1956 that specifically gives 2 to 6. I can only assume they may have been selectively assembled to keep the gap down, but that would still result in a typical gap of 4.

The gear bore is 1.500–1.501 and the gear OD is 1.4945–1.6945. Again, the service manual gives no allowance for wear, specifying no more than 5 thou.

Hope someone finds this interesting and that the Studebaker museum enjoys my "donation". Let me know if you have any questions that I could look up for you. I don't have EVERY drawing just the most important drawings.

hph

Does service data indicate the end cover wear tolerance, or a lapping procedure to restore the cover finish?

dp

Very interesting that the V8 gears were a mod of the earlier gears. I can surely understand that as they already had the tooling for forming the teeth and the earlier pumps were trouble free. Are the overall length of the gears the same? Also, very handy to have the specs for the shaft and housing bore. On the earlier pumps, the input shaft had a much longer bearing area. I'm pretty sure that an extra overhang loading from driving the vacuum pump was a chief factor in accelerated shaft wear. What I've never figured is how some cars escaped this til high mileage and some tanked at 20K.

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You'll have to tell me as I don't have an earlier pump or drawing to compare. When I have a sec I'll grab the dwg again and post the dimension.

The two gears in this pump are the same in all "gear" respects including length.

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The service manual says to dress it down with a surface plate but there is nothing specific in the drawing. That would be covered in the endplay which as I mentioned, contradicts the service manual. I should measure the endplay, and gear & bore lengths on my pumps and see what they actually are.

One curiosity is that the assembly in the drawing I have does not have the vacuum pump attached. Instead, it has just a plate held on with cap screws.

The one drawing that I asked the Studebaker museum for but that I don't have is the one for body with the late design relief valve, 6492431. I have only the earlier body 440679.

When I have a sec I'll cross reference the assembly BOM on my drawing vs. the parts book. Because I have the important component part drawings, I did not ask them if they had 440679, the assembly drawing as given in the parts book. But while searching they stumbled upon the drawing I did order which is a much newer number and was drawn in mid 1956.

One idea to repair excessive gear endplay would be to punch a 1/2” hole in some 1-1/2” disc shims, 0.002 thk then install one above each gear. The only difficult thing to DIY is getting the ID punched exactly in the center… or just use a 5/8 ID punch LOL.

mcmaster.com/product/2904T62

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Whoa!! That procedure would just be trading a headache for a stomachache. The low oil pressure doesn't care on which end of the gear the excess clearance exists, only that it does. The only cure for excess end play is removing material from the bottom of the pump body.

jack vines

Thanks Jack but I'm not sure I'm following. Why wouldn't a shim with the same ID and OD of a gear, placed next to the gear, help reduce the pressure loss that would otherwise occur through that gap?

Quote:Only that in more than sixty years of looking inside oil pumps, I've never seen it done.

It's obvious the shims can't be full gear diameter, or they'd overlap. If the shim is the root diameter of the gear, there's still that space above the meshed gears to leak the pressure.

jack vines

Ah, good point...