TMC 40 verses TMC 60 Technodrive/Twin disc

[thaisail]

I am installing a new Beta 30 aboard a 1968 Comanche 42 (Chris-Craft)

COMANCHE 42 (CHRIS-CRAFT) sailboat specifications and details on sailboatdata.com

I need to choose between a TMC 40 and TMC 60 Technodrive gearbox. The TMC 60 costs about $400 more than the TMC 40. Is it worth the extra money? Does anyone know the difference?

[DougR]

The TMC 60 has about twice the input power capacity of the 40.

In general, going to a transmission with a higher capacity rating doesn't cause a problem, as long as the input shaft splines match the damper plate, and the torsional chacteristics of the two gears are similar. In this case you will probably be OK with the upgrade.

What you need to know however is that the TMC 60 is physically larger than the TMC 40. It is 65 mm longer (2.5"), and it has an 11.3 mm deeper drop center distance between the input shaft and the output shaft. So, the engine will sit 65 mm further forward ( conventional installation) and 11.3 mm higher. Is there room for that?


DougR

[thaisail]

Thanks for the measurements! They were extremely helpful. As we are replacing the original Atomic 4 petrol engine with the Beta 30 Kubota engine, we will have use the original engine beds. It looks like the TMC 40 is the more practical option because Beta actually offers the Atomic 4 feet option for a reasonable price but they can only work with the TMC 40. With the TMC60, the feet will be too narrow and the gearbox will not fit between them.

What I am really after is: Which gear box is the best, meaning most reliable, strongest, most easy to maintain, etc.? The Beta factory recommends the TMC40 but what I want to know is what are the advantages of the TMC60? I see only disadvantages listed so far. If the TMC40 will hold up over the years with this boat, than I am fine with it. But if this gearbox has a bad reputation for either being too weak, premature failure, overheating, I would go with the TMC60 if this gearbox will avoid those issues. That is why I am searching the internet for any horror stories about either of these two gear boxes so that I can make an informed decision.

[DougR]

-Try making an Internet search using " TCM40 gearbox problems"

- what does your engine supplier recommend?

DougR

[thaisail]

I found the smoking gun for the TMC40. I don't know if this is the case with the TMC60. But I think it may be the same problem I had with my Kanzaki from Beta for my Beta 30. I had to take it apart and deglaze the forward drive cone with fine grinding paste but now it works find. No parts changed and so far 150 hours with no slippage. It appears that the TMC40 has the same issue.

TWIN DISC TECHNODRIVE TMC 40M GEARBOX PROBLEM