First up is the U25C. As with the EMD units, GE's 6 axle units pretty much mirrored the 4 axle units, just with 3 axle trucks under each end. The difference from a U25B, and a U25C, is that the U25C, has a longer frame and shorter short hood. Here is a U25C.
Up next is the U28C. Once again, drawing a parallel to the 4 axle units, the first U28's were indistinguishable from the U25C's. When they did make the body change, they lost the step, at the rear of the long hood, and gained the first sign, of the radiator overhang, in the appearance of a bulge. Also this series introduced the soon to be common Adirondock truck. GE also produced 10 units for the Santa Fe, with steam generators. You can see this by the bulge on top of the long hood, behind the cab. This is the U28CG. Here is a later version of a U28C, and a U28CG.
Collection of Joe Hughes
Next in line is the U30C, and once again the Santa Fe only U30CG. Once again it can be said that early U30's, looked the same as late U28's. When the body style did change, the small difference, was that the bulge, runs all the way down the side of the long hood, to the walkway. Here is a U30C, and U30CG.
Collection of Joe Hughes
Then came the U33C. The biggest spotting feature, of this loco, is that with the higher HP, it needed a larger radiator, and now the true "wings" are appearing on the end of the long hood, at the top. Here is a U33C.
At this time the railroad's were looking for medium HP units, so GE put a 12 cylinder prime mover in the U33C body, and it became the U23C. There is no way to see the difference, in the U33 vs. U23. Here is a U23C.
Collection of Pat Huemmer
The next unit to come out of the Erie, PA. shop's of GE, is the U34CH. These units were only built for the NJDOT/Erie Lackawanna commuter service out of New York. These units were taken into the NJT (New Jersey Transit) roster. They are U36C's that have been rated at 3430 HP, and the rest is used for train auxiliaries, such as heating and lighting. Here is a U34CH, in EL paint, but now a NJT unit.
Collection of Donald Albertson
The second to last U series, is the U36C's. The U36C, is only told apart by the fact that the radiator is a little larger, and right at the end of the radiator overhang, GE had been putting in a little cosmetic lip, to smooth the transition of the long hood to the witdth of the radiator. That is now gone, and the unit is starting to look alot like a -7. Here is a U36C.
Finally in the end of U series production, is everyone's favorite Amtrak unit, the P30CH. There is no other unit like it. And unfortunately all are gone.
Collection of Tim Darnell