Last week I replaced the rear main seal on my '53 WD45. I did this without removing the engine using a technique old hot-rodders called "Sneaky-Pete". It worked very well. I replaced the seal in less than a minute. The tractor has run long days since then, about 32 hours all-told, and it has not leaked one drop. If this changes I'll post again to let you know. I put up photos and descriptions on my website showing how the operation was done.