Manual Trim M20K

[Nate Dickman]

I had an issue with my electric trim not working, so I am having the motor and clutch tested. In the meantime, I cleaned and lubricated the jack screw in the tail and now I am looking at the manual wheel in the cockpit and the gearbox underneath. Has anyone ever serviced the gearbox underneath the manual trim wheel in a Mooney? If so, do you have any documents that tell how to do this or any advice? 

[N201MKTurbo]

It is stone simple. The secret is to get it all synced up when you put it back together. Run it to some known position like takeoff trim. After this don't rotate the trim shaft! Remove the trim shaft and the indicator cable. Measure the position of the indicator nut and write it down. pull up the carpet around the trim wheel and remove the screws holding it to the floor and remove it from above. If I recall, the chain has a master link. Remove the chain. If it doesn't have a master link, drive out the roll pins on the two sprockets and slide the sprockets off. Disassemble the trim wheel, clean and grease (I used grease 22), clean the chain in a container of solvent until it is squeaky clean. I know the manual says to grease the chain, but that is yucky. I hose them down with a good quality bicycle paraffin based chain lube. Work it in and let it dry. Take the lower gearbox apart, clean it completely. Do a trial reassembly and check how much slop there is in the pinion shaft for and aft. Any slop there will translate into a dead spot in your trim. If there is slop get some shim washers from McMaster Carr and shim it till there is no slop, but not binding. Once it is shimmed up properly, put it back together and pack the gearbox with grease. Put it back into the plane. Spin the wheel until the indicator block is at the same position it was at before you took it apart. install the indicator cable, but don't tighten the wire or indicator nuts (if it has them). Reconnect the drive shaft. Adjust the indicator cable so it indicates the same trim position as before removing it.

[DonMuncy]

Geez. It sounds like you have done it before. 

[Alan Maurer]

Sounds like you need a degree from MIT to do this!

[Igor_U]

I'm not sure about MIT but seems like a lot of work comparing to the jackscrew lubrication. Having said that, I'd like to do it eventually, maybe on next annual.

I seem to remember one of the characters on old Mooney list describing he just installed couple of zikr fittings to the Trim assy to flush and fill it with grease. Not sure if I'd like to do that...