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149 tooth ring gear part number.

terry.mortimore

Well Known Member
Hi gang, I want to replace the ring gear on my flywheel assembly and I?m struggling to come up with a part number for it. My flywheel assembly has a 76628 number on it.

My engine is an original O-320 which I have been told are now called O-320 A.

Aero Instock list two numbers SL60882 and SL 72566. Can someone tell me which one would be 149 tooth?

Aero Instock are asking questions that I can?t answer till the end of the week when I get out to the hanger.


Thanks in advance, Terry
 
149 tooth ring gear part number

Thanks Carl, that?s what I?m looking for.

Found a new one on E-Bay from the air boat guys in Florida listed for a good price.


Forgive my poor spelling, spellcheck let me down. 😀


Terry
 
the support assy's for a fine tooth ring gear and a course tooth ring gear are different and not interchangeable. You engine sounds like it might have a course tooth ring gear support if it is an early 320. So you might double check that the fine tooth ring gear you purchased will work on the support assy you have.
Good Luck,
Mahlon
 
149 tooth ring gear part number

Thanks Mahlon, so it?s possible that there is both a fine tooth and course tooth 149 tooth ring gear available?

Terry
 
149 tooth ring gear part number

Thanks Ross.

I?m trying to replace what I have. I know that I have 149 teeth on my ring gear, my starter is for a 149 tooth ring gear.

Carl?s note last night pointed me at part number 72566. I found that one and ordered it last night. My confusion is if there is both a fine tooth and course tooth version of the 149 tooth ring gears?

I guess I?ll know for sure when my new ring gear arrives.

Terry
 
sorry for the confusion, Terry. What I was trying to point out to you was that the flywheel or starter gear support for a 149 tooth ring gear and a 122 tooth ring gear are different. If you know you had a 149 tooth ring gear and are replacing it, it will fit on your current gear support..no worries. Older 320 had 122 tooth ring gear and that support and that support would not work with a 149 tooth ring gear. Someone, at some point, has updated your engine starter, ring gear and support from course tooth to fine tooth along the way.
Good Luck,
Mahlon
 
The 122-tooth ring gear is 0.375" front to back.

The 149-tooth ring gear (part number SL72566) is 0.440" front to back.

IF you were to put a 149-tooth ring gear on a support designed for the 122-tooth ring gear, the distance between the back of the starter ring gear and the front of the starter gear will be 0.065" closer to the starter. IF you use a SkyTec NL starter that was designed to be right at the Lycoming spec, you may have a case where the starter ring gear comes in contact with the starter gear when the engine is running.

I just measured a 122-tooth gear mounted on a support and a new Superior Airparts 149-tooth gear. The problem with the Skytec NL starter use to be documented on the Skytec website before the company was sold.

The above info may be what Mahron is pointing out.

From experience, I can say that changing a support designed for 122-tooth starter ring gear to a 149-tooth starter ring gear may work but it may not work. There may be a clearance issue with the 149-tooth gear. Supports designed for the 149-tooth gear have more surface contact with the 149-tooth gear than what is available on the 122-tooth gear. (aluminum to steel contact between the interface)
 
Photo

They say a picture is worth a thousand words.

2018-03-18_17.18.31.jpg


The above image show a 149-tooth starter ring gear mounted on its support on the left. On the right is a 122-tooth starter ring gear mounted on its support.

Take notice that the AFT side of both gears are at the same location. Also note that the FRONT side of the gear on the left (149-tooth) goes forward more than the 122-tooth on the right.

IF you mount the 149-tooth gear on the support that is on the right, it will project AFT of the support housing and MAY come in contact with the starter gear.
 
149 tooth ring gear part number

Success!

Hi guys, I picked up my ring gear yesterday and checked things out. I had about 1/8th of an inch between the starter gear and the ring gear when the starter was at rest.

The ring gear matched my existing one, so I took things apart and changed the gear. Going to finish putting it back together tonight so I can go flying tomorrow.



Thanks for all the help, terry
 
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