Reassembling the AW450 (Part 1)
Before doing a thorough cleaning, I went over the interior of the case to clean up any burrs that might damage a seal during reassembly. One of the things that I noticed while disassembling the three transmissions (two AW450,s and a A440F) was that the seals between components that slide together were often mangled, like those between the Center support and the main case (Photo 3 of Post # 323) or those between the OD case and the main case (Photo 2 of Post # 321 ). These seals are compressed first then slid over the mating holes as the two assemblies are mated. Photo 1 is a closeup of a mangled seal. Do you think this O-ring might leak? This would lead me to believe that it would be a good idea to slightly chamfer the edges of the holes so that the seal is not cut as it slides over the hole. I’m going to try one additional technique to hopefully prevent seal damage. The FSM says to lubricate the seals with ATF (Dextron III) during assembly. I’m going to go one step further and use Parker O-Ring Lube (Photo 2). This stuff is slicker than snot and I’ve had very good luck with this stuff reassembling aircraft engines. Hopefully, I’ll not regret this decision!
Some general precautions per the FSM – don’t use rags or paper towels during reassembly as the lint from these may cause problems. Presoak the clutch/brake friction disks in Dextron III for 15 minutes or more prior to installing them. Don’t expose any of the o-rings, seals, and friction components to solvents such as gasoline, naptha, MEK, etc. Dextron III and kerosene are OK.
Some precautions that I learned the hard way: Have the FSM on hand and follow it! Read over the complete task that you going to perform before starting it. Make a photo copy of the FSM and check off the tasks as you complete them. Test your work before moving on to the next step. Using an air nozzle with a rubber tip will enable you to test a clutch or brake for proper operation and for leakage. Drain your air compressor of any water accumulation. You don’t want to be blowing this crud into your transmission. As you manhandle the various components, make sure you don’t damage the soft aluminum mating surfaces. I always use a working surface covered with
CLEAN wood.
After removing any nicks and burrs in the case, slightly chamfering the edges of the above-mentioned holes, and removing all traces of old gaskets, I thoroughly washed the whole case in clean kerosene, making sure that all the passages were flushed followed by a good blow from the air hose. I next placed the
empty case top side up on a piece of 2 x 10 and thoroughly washed down the outside with brake cleaner to remove any traces of grease and oil. Once dry, I plugged or masked all of the openings followed by several coats of clear paint. I like the looks of clean uncorroded aluminum so hopefully this treatment will help preserve that look. Photo 3 is the case ready for assembly.
It may never work again but it sure is purdy!
