Is it OK to leave a Muncie sit in the garage for a few months without oil in it after it has been rebuilt? Any harm to the seals, rust concerns or other problems to look out for?

Thanks

Not a problem. Most rebuilders use some sort of oil when they assemble the unit, I use gear oil and try to put a thin coating on all the gear surfaces, sliders and hubs.

When I assemble Muncies, I keep them very dry, EXCEPT for VERY light lube on the moving/contacting parts (gear teeth, bearings, sliding parts, etc). Just enough to protect them. If a tranny needs shipping (UPS) it MUST be dry (keep in mind that new trannys, such as Richmond are dry). The most lube on/in the Muncies that I build is the grease on the needle bearings in the cluster and the caged rollers between the input/main shafts.