The Cessna 120-140 Association Forum

the main gear box has a welded gusset on the top side that has a couple of small cracks. is that allowable? if not whats the fix?

Many moons ago during an inspection we found a previous gearbox repair that was really poor so we removed the gearbox, tig welded the cracks, and then stress relieved the whole thing (heated it up and let it cool). Sandblast and chromate, only one rivet didn't fit on re-installation.

When we removed the gearbox we also found some hidden bulkhead damage so we tended to that at the same time, glad we did.

Inspecting the gearboxes is one of the more difficult things I've found in that you really have to get your mirrors and lights in the right spot to be thorough.

Make sure they are truly cracks of course. Repairable, but Univair has new right side units for a measly $1600 https://www.univair.com/cessna/cessna-1 ... ead-right/