The International Cessna^® 170 Association

The June issue of "Light Airplane Maintenance" has an article on old style alternator couplings on TCM O/GO-200/300, IO/TSIO-360 engines. It references TCM SB#95-3A which states in part that when the rubber cushions become hard over time they no longer absorb shock loads applied to the gear train. The result is damage to the coupler and gear train and contaminating the engine with metal. Continental recommends that the cushion and retaining cup be replaced every 500 hours.

Has anyone had experience with this problem? It's the first I have heard of this SB.

It also mentioned that another option is to replace the older style coupler with the newer type - cost $1000.00.

The NTSB recommended an AD also for this problem see the following link for more information.http://www.ntsb.gov/Recs/letters/1997/A97_35.pdf

Interesting, that proposal was 7 years ago. Did it just die on the vine?

I complied with the service bulletin when I had the engine overhauled about 3-1/2 years ago. Spruce had the parts required,total was about 16 bucks. You need "retainer" p/n 352030,and "bushing" p/n 626543 (Spruce part numbers). It''s a pretty easy job, the most difficult part is removing the alternator.
The service bulletin sez to "inspect" ( by replacing parts!) every 500 hours. It's been about 580 tach hours since I replaced the parts,so I was thinking I should do the SB again. However, I had my alternator off to re-tork the oil filter adapter ( what a pain in the a**!),and I eyeballed the coupling assembly--the rubbers looked fine,so I'm not gonna mess with it.

Eric

Thanks Eric.

In the Spruce Catalog they refer to these as "Generator" parts. Do you have an alternator or a generator? Are they the same coupling?

The coupling assembly is the same,as far as I know. You keep & re-use the drive/coupling assembly when you do a generator or alternator exchange, or a gen-to-alt conversion.
You should get a copy of the service bulletin, if the magazine article did not include the text. It's a 3 page SB consisting of 2 pages of text & one of illustrations.

Eric

The couplings should be changed whenever the generator comes off if it's been more than five years as the rubber parts in the coupling gets hard and allows the shock to be transmitted to the shaft and can cause premature breakage of the shaft and possible ingestion into the engine. When the parts are replaced if the cotter pin hole doesn't line up when final torque is achieved don't tighten more, file or grind the back of the flanged nut until torque limit is met and hole lines up. This same S/B is required on all the smaller continentals and all parts can be had from El Reno for peanuts compaired to an engine teardown due to foreign object ingestion and accessory case gear damage. 2 cents

Geez..I am thoroughly confused and respectfully ask for clarification from our more learned 170 gurus who have experienced this.
I understood the alternator coupling is different from the generator coupling and is a more troublesome part. This is the primary reason I have stayed with the 35 amp generator. However, if I understand what has been written here, the couplings are the same and should be changed every 500 hours . Is this correct and if it is, can someone list the part numbers which should be changed?? I gotta change out the generator gasket for a slight oil leak and this would be the perfect opportunity to change the generator couplings if necessary.

See my 7/23/04 post above for the Spruce part numbers of the required parts. I don't recall if "bushing" p/n 626543 is one bushing, or the two actually required. Probably just one, but ask Spruce when you order the parts. You also need a new cotter key for the retaining nut. The service bulletin sez it all re: performing the work.

Eric