Packard Forum Index » V-8 (1955-56)

450352 vs 6480887 High Speed Governor Body
The latter has a pin about 20 thou longer than the former. This keeps the valve farther off the body. When possible, the latter should be used with the 56th style Governor valve to reduce the chance of the valve sticking. The parts are identified by casting number.

450817 vs. 6480640 Rear Pump To Ring Gear Thrust Washer
The former is fiber and 0.064 thick. The latter is steel and 0.048 thick.

470091 vs. 6470250 Rear Housing Assembly
The parts are identified by casting number yet the castings are the same. Instead, the only difference is the spider (the bushing support piece). The 55th type has four holes in pairs. The 56th type has four holes spaced evenly. The part was redesigned for greater strength, but they are interchangeable in practice.

All Seals (not including gaskets)
The 1956 type were improved design over the 1955 type. Irrelevant now.

High Range Clutch, Input Shaft, Converter, Etc.
The 56th input shafts had a finer spline than the ones previous. Anything that is engaged into the input shaft has a different part number for 56 and may be correspondingly identified irrespective of other differences that may exist.

465754 vs. 6480734 Oil Cooler
The 55th type has a seam running down the center of the cooler. The 56th type the seam is on one side, much like a sardine can. The 56th type has better cooling performance. While not necessarily helpful for a 55th, it is recommended to use on a 56th car or 55th Caribbean to dissipate the converter heat more effectively.

470049 vs. G137406 Oil Cooler Line Adapter To Case
The former has a smaller orifice than the latter. The former part itself is obsolete as there is no need to restrict the oil flow to maintain pressure in the converter. It can simply be modified by drilling the hole oversize to match the diameter of the other hole.

440845 vs. 470143 Oil Pan
The 56th type has one less hole than the 55th type. This is most easily identified by the fact that when looking at the pan from the underside, the 55th type will have one reinforcing strip at the front of the pan while the 56th type will have a reinforcing strip both at the front and back edge of the pan. It is important to note that all of the Packard pans have the filler tube fitting at the right of the front side of the pan (looking at the pan right side up). If the fitting is on the front of the right side of the pan, then it is for a Hash car. See Hash vs. Packard Differences. In other words, the drain plug and the filler tube connection are on adjacent sides on a Packard pan, but are on opposite sides for a Hash pan.

458950 vs. 6484046 High Range Clutch Assembly
The 56th type is shorter than the 55th type. If the transmission body endplay is outside the range of selectable spacer washer, exchange one for the other. All which have a "0" stamped opposite the check valve are 56th type, but most are unlabeled. See SB 346. This is not to be confused with the "0" that is stamped into the ring gear as all ring gears are the same. The units may be easily compared using a dial indicator as shown. The 55th will indicate approx. 0.060" thicker than the 56th. Or using a caliper and gauge block the 55th distance is approx. 4.471".

421073 vs. 6470245 High Range Steel Clutch Disk
The 56th type have more clearance between the disk and the body than the 55th type. Irrelevant.

450552, 450553, 470172, 6484614, 470219 Converter Rear Thrust Washer
See explanation here:packardinfo.com/xoops/html/modules/newbb ... 6809&post_id=288698#forumpost288698

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Here are some high-speed governors. The one on the left is the 55th type that has the 450352 body without the pin. The middle is the same 450352 part number except it has a pin installed making it the early 56th type. The right is the 6480887 type making it the late 56.

The valves are shown clearly. In particular, left one has the 55th spool valve as shown in the manual while the middle and right use the 56th type.

The springs are also slightly different. The left spring has one more coil than the right two springs. See the photo whereby rotating the springs to line up the spring coils at the bottom of the spring, it is obvious that the left one has one more turn throughout its length. The right one shown is the 56th type which was the same for both governors. The wire diameter is also different but only very slightly; the 56th type is 36 thick while the 55th type is 34 thick. Therefore, the 56th spring is also slightly stiffer.

Therefore, to determine a 55th or 56th type governor, the 56th type must use the 56th type spool valve and a body with a pin to hold the spool valve off the end of the governor and the 56th type spring which has the one fewer turn.

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Is that the 5588 version or the everything else version?

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Does Packard define an "early 56th type"? I haven't come across that definition. Or could someone have just added a pin to a 450362 body?

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The 55th is also wound with a different pitch. If you compress them to the same length, how different is the pressure?

You can't tell from the pictures, do the valve lengths differ from spring seat to end and are the bore depths different?

As far as I'm aware, I don't have a convertible version of anything. Once I get a 55 convertible transmission, I will have to make some measurements of the respective parts for reference.

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Yes, Packard added the pin to the 450362 body. As mentioned in my first post, if you measure the two types, you will find that they are exactly the same in all respects aside from the casting number. I believe Packard used up their remaining stock of 55th types and installed the pin, and only when they needed more did they change the casting number. On a pair that I measured earlier, the pin length was slightly different but it's probably not important and could have simply been some assembly error or one of the pins getting shifted slightly out of position for some reason in the past. It could have also simply been a revision at the same time that they updated the casting number.

If you compare the design of the 55th and 56th governor valves, it's clear that you have to use the pin type body with the 56th valve and the body without the pin with the 55th type; it absolutely won't work the other way. A 55th valve and a 56th body would compress the spring far too much, whereas a 56th valve in a 55th body would not want to move off of the end of the bore since there is no area under the valve for the fluid to push it out.

My assumption is actually that Packard considered all of the ones with the pin to be the updated part number, it's just that it wouldn't be obvious nowadays by looking at the casting number. The early 56th nomenclature is my own wording.

For your last question, yes, the spring constants and the uncompressed lengths as installed are different but I did not measure them. I have a chart somewhere that simply shows the governor pressure at a given speed for the 55th and 56th types, which is really all that one would care about, so it's not data that I particularly need to collect.