Nanni gearbox

[PabloPicasso]

Hi all

A pal of mine has a nanni engine mated to a TCM40m gearbox. Twin disc technodrive.

In 2025 it started to delay engaging forward gear. Can be 20 seconds, but sometimes it's better, seems random. It's ok in reverse.

Gearbox fluid changed and it was a bit dark.

It is not the morse cable. Still does it with cable disconnected.

Any suggestions as to a fix.

 

[Amlov]

Unfortunately the TMC40 has a significant history of such problems. Usually it is premature wear on the forward half of the clutch cone and requires either replacement or a new gearbox. There was a technical bulletin issued a few years ago detailing how to adjust the allen bolt on the gear arm to reduce the clutch clearance, which is moderately successful, and someone has said that roughening the clutch bearing surface worked for them. But the usual solution is to bite the bullet and buy a new gearbox.

The darkened ATF is again not uncommon and suggests that the gearbox is overheating - using DEX3 rather than the specified DEX2 is marginally beneficial as it has a better temperature range. These problems are well known to Beta and Nanni but yet they still use the TMC40 as their standard gearbox on the smaller engines.

No doubt someone will be along shortly to suggest gear linkage adjustment and the gearbox not going into gear properly, but your description of the problem is fairly diagnostic of the problem as clutch cone wear.

 

[PabloPicasso]

Unfortunately the TMC40 has a significant history of such problems. Usually it is premature wear on the forward half of the clutch cone and requires either replacement or a new gearbox. There was a technical bulletin issued a few years ago detailing how to adjust the allen bolt on the gear arm to reduce the clutch clearance, which is moderately successful, and someone has said that roughening the clutch bearing surface worked for them. But the usual solution is to bite the bullet and buy a new gearbox.

The darkened ATF is again not uncommon and suggests that the gearbox is overheating - using DEX3 rather than the specified DEX2 is marginally beneficial as it has a better temperature range. These problems are well known to Beta and Nanni but yet they still use the TMC40 as their standard gearbox on the smaller engines.

No doubt someone will be along shortly to suggest gear linkage adjustment and the gearbox not going into gear properly, but your description of the problem is fairly diagnostic of the problem as clutch cone wear.

Thanks Amlov, we suspected the gearbox needed to be removed and new parts, likely a clutch cone. . But we were vainly hoping otherwise

 

[oldmanofthehills]

Hi all

A pal of mine has a nanni engine mated to a TCM40m gearbox. Twin disc technodrive.

In 2025 it started to delay engaging forward gear. Can be 20 seconds, but sometimes it's better, seems random. It's ok in reverse.

Gearbox fluid changed and it was a bit dark.

It is not the morse cable. Still does it with cable disconnected.

Any suggestions as to a fix.

My TCM40 failed to engage forward after 10 months, or only went in after maybe 12 attempts. Resulting me engaging it finally in S Brittany and not daring to stop till I got to boatyard in S Cornwall.

TCM claimed wrongly that I must have abused it. A piece of sh*t.

Mind you Beta who supplied it also walked away from responsibility and merely gave me a new TCM at discount leaving me to pay fitting bill. Beta engine great but combining it with such a poor product ......... The projected costs of rebuilding instead were extraordinary. Later I I realised that it was a cone not a car type twin disc, so I could have saved a tiny bit and done the gearbox work myself leaving only the expensive disc plus engine removal and fitting from the cramped bay ( I have replaced cone on Yanmar in spacious bay)

Other gearboxes fit most engines - I wish I had got Beta to fit something else at purchase or at repair

 

[doug748]

Thanks Amlov, we suspected the gearbox needed to be removed and new parts, likely a clutch cone. . But we were vainly hoping otherwise

They may not be great gearboxes but the good news is that parts are cheap and even a new box is only about £900 ish. (a blow but in the scheme of things could be worse..)
I had one for 15 years and about 1500hours with no problem so the failure rate may not be that high but that does not help you I admit. Suggest you deal with Beta who supply a lot of them + bits.

PS I have a brand new one, still boxed, £500 but would need picking up from Devon

.

 

[Tranona]

Other gearboxes fit most engines - I wish I had got Beta to fit something else at purchase or at repair

The problem is that the alternatives have different output centres and are longer which is OK if you specify the box from new and build your beds/brackets to suit but a bit of a chore if replacing an existing TMC40. I change my order on a Beta 30 to a PRM at the last minute because of concerns with my set up the 40 would be close to its limit and built the beds up to suit the lower output. Generally though the TMC40 is fine on the small engines but probably not the first choice once you get above 20hp.

 

[oldmanofthehills]

The problem is that the alternatives have different output centres and are longer which is OK if you specify the box from new and build your beds/brackets to suit but a bit of a chore if replacing an existing TMC40. I change my order on a Beta 30 to a PRM at the last minute because of concerns with my set up the 40 would be close to its limit and built the beds up to suit the lower output. Generally though the TMC40 is fine on the small engines but probably not the first choice once you get above 20hp.

My engine is 25HP and TCM gearbox failed after 500 hours so really a chocolate teapot. I note the refit issue but if I had known on original replacement of defective ancient Bukh, I could have set the beds for the PRM