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Does anyone recall the size of the rear axle pinion nut on one of these?

I need to replace the pinion oil seal and 1 1/2 inch is too big, 1 1/4 inch is too small. I'm thinking 1 3/8 maybe???

Thanks!

Sorry I can't be sure for you, but my 47 used a 1 1/4 and I had to shave the sides down so it would fit inside the yoke.
Wes

qbert
I pulled together some information on the pinion nut question, and placed that into the attached file. I would think the $7.25 price for the special tool would be well worth it . . . where do I place my order ?
dp

Let's try the 'attach file' process one more time.

I've tried 'Browse' (select the correct file), and then 'Attach File' . . . nothing seems to happen.

Oh well.

The short answer is 1 7/16 inch. See Service Counselor Volume 27 Number 8.

To view the Service Counselor data click on the Packard Service Index menu item, click on the 1951-1954 selection, and finally the Rear Axle selection. The referenced SC is titled Flange Holding Tool.

dp

That is the exact size I purchased this morning!

How big of an air wrench do I need to do this??

Avoid the urge to use an impact wrench as the torque values are 'reasonable'. The key to a successful pinion seal replacement is returning the pinion to exactly the same position it was in prior to the repair (assuming all was well with the rear end except the seal). Achieving this goal will maintain the same bearing preload and gear mesh geometries . . . very important if you want a quite differential . . . no humming allowed, one must know the lyrics.
Step one of this procedure is to 'match mark' the pinion nut and pinion shaft. This is normally done by 'center punching' the nut and center portion of the pinion shaft. I would also 'match mark' the yoke, and essentially have three marks aligned. Before you remove the pinion nut I believe I would attempt to make an estimate of the pinion bearing preload. Make sure both wheels are removed and the brakes 'backed-off' to zero drag . . . emergency off. Depending on how cold it is in the shop I would suggest that the gear oil is drained before the rotational drag is investigated. With the emergency brakes on I would also attempt to measure the amount of pinion gear motion, both in and out of the carrier, and rotational play (emergency brake is holding the ring gear from moving). The shop manual suggests a 0.004 - 0.006 pinion gear backlash. Since you'll be using the yoke, which is about 1/3 the size of the ring gear, you should have about 0.001 - 0.002 back lash at the yoke, or just about at the limits of 'feel'. If you make this check and report 'little or no back lash', then you're likely OK. I would also measure the distance from the flat end of the pinion gear to the face of the nut, that will come in handy going back together.
Step two is to loosen and remove the pinion nut. The referenced Service Counselor had a photo of the special tool to hold the yoke. I would attempt to make something that serves the same purpose. Note that one of the leaf springs holds the tool while you are focused on either loosening or tightening the pinion nut. I would also try to estimate the torque required to break the nut loose, but just for reference later on. Pinion nut torque is not a critical characteristic, bearing preload, measured by the amount of bearing drag, is the key characteristic, along with pinion to ring geometries (back lash and pattern).
After replacing the seal, step three is to reinstall the yoke and nut, and align those three punch marks. Initially the torque on the pinion nut will be quite low and then when you're getting close the torque will abruptly rise, you'll know the 'feel' from the torque it took to remove the nut. The three marks will almost be aligned (the yoke and pinion shaft will be grossly aligned by virtue that you've aligned to the correct yoke/pinion splines), it is the mark on the nut that is being moved into alignment. At this point the dimension from the end of the pinion to the face of the nut should be the same as the initial measurement. Align, but do not pass-by the correct position . . . the game is over if you 'over torque' the pinion nut, but I suspect a lot of us are guilty of backing-up the nut's position. Just as long as you haven't gone too far I guess it's OK to back-up a little bit. The torque required to move the nut that very last amount should be about the same as the value measured during step two.
Step four is some confidence building by repeating a few of the checks made before the disassembly. Does the pinion have about the same 'free play', and does it take about the same amount of torque to spin the pinion. A flaw in this logic is that the new seal should have more drag than the seal that was removed, so the torque to slowly rotate the pinion is likely to be more after the seal replacement, all else being equal. The germane section in the shop manual will have the correct pinion bearing drag for the pinion and seal alone, no other parts, which is not the case here. We will be comparing the drag before and after the seal replacement. Avoid the urge to compare this confidence building torque to the values in the shop manual . . . the procedure in the manual does not have the carrier bearings, axle bearings, or axle seals in their measurement.
Note the key role the old pinion nut plays in this procedure. If you also replace the pinion nut I would be at a loss on how to achieve the sameness in the pinion position without the carrier out of the car. I know the procedure sounds a bit complicated, but it's straight forward. Those confidence checks I've suggested don't need to be measured with instruments, your hand is good enough. Let's say before you disassemble the unit, you spin the yoke with the brakes backed-off, and it will rotate a little bit after you let go. What I'm suggesting is that after the seal is replaced and the same check is made the amount of 'free rotation' should not be 10 or 15 minutes of coast down, nor should it take all your strength with a breaker bar if you could hand rotate before the seal replacement.
Have fun on the cardboard . . . please remember gravity always wins, use lots of jack stands if the job is done on the garage floor.

DavidPackard's description on replacing a pinion seal is the best I have read. Each step clearly spelled-out. Suggest it be posted in the FAQ section. Good job, David. Thanks.

(o[]o)