Early PTO vs Middle Style difference

[53Crusher]

I am planning to install a winch on my 53 so am now working on PTO's, drive shaft and MU-2 repairs. I found two PTO's but as luck would have it, one ("S") is an early ( pre 51 ) and the other (12525) is the middle style (51-55). I have read that the middle style can be used on older trucks with 1/4" spacer but older ones can't be used on middle style transmissions. I have noticed three major differences on first inspection. Flanges have different thicknesses- Top gear shaft in early pto has larger diameter, and the top set screw in the early is bigger as well.

My question is this.... I assume I can't interchange the top gear and shaft, but are the other shafts and gears interchangeable? My reason is the gears in the early style are in much better shape than my mid style and I would prefer to use them if I can. Anybody know what parts can be swapped between the two? Hate to tear apart the early pto if nothing will work for me :-)

[53Crusher]

Early vs Middle style PTO

Ok.... So I couldn't stand the suspense/got bored or perhaps both today :-) Besides, I have already lost all my teams in the office football pool this year. I went ahead and dissected the early style PTO to see if there were any gears or shafts I could transfer to my middle style. The sliding gear in the bottom of the PTO appears to be the same (early 12506 right side of pic) (middle 5C12506 left side of pic) with the exception of how they are cast. Early gear looks beefier. The double gear also looks good (early 4104 left pic) (middle 5CNP4104 right pic). As stated above the gear that interfaces with the transmission (idler?) has a larger diameter to accommodate the larger shaft and is also narrower than the middle style so it requires a spacer and two washers on installation compared to a spacer and one washer for middle style. Early is on top (12512) and middle is on bottom (12520).

[53Crusher]

Early vs Middle style PTO continued

For the shafts, the sliding shaft (early 12507 bottom pic) (middle no # top pic) appear to be identical except for how the woodruff slot is cut into the shaft. In the early style it goes all the way through the end of the shaft. The shaft that allows you to select forward/neutral/reverse is shorter on the early style (top pic no #) and has a smaller hole for the set screw on the fork. The middle shaft (left pic) that the double gear sits on is a little shorter on the early style. The fork on both models is identical with same casting number. The bearing cages, cup and cones seem to fit these three shafts interchangeably. So..... it would seem I could choose to swap everything but the idler gear and shaft. If anybody has played with this or a different opinion, please let me know. Thanks!

[gmharris]

You are now probably one of the foremost experts on the interchangeability of parts between early PTO's.

I have heard of people using a spacer to adapt a PTO, but I have never heard mention on anyone interchanging parts between two different models.

The fact that Dodge changed the part numbers on the gears is concerning. If you do go ahead, make sure you check the dimensions with a micrometer. I also wonder what has happened as far as wear patterns on the gears and what affect this will have on longevity of the gear and shaft.

[53Crusher]

Gear interchangeability

Thanks for the input!
I don't want to be an expert in this area, but can't find a source yet to simply replace the gears and shafts with new ones. So far, I can only find a new sliding gear and two of the four shafts NOS. As you can probably see, I tend to overdo my repairs so I don't have to go back to them anytime soon. Will definitely mic the gears if I do go down this road. Thanks again!