TWIN DISC TECHNODRIVE TMC 40M GEARBOX PROBLEM

Hi

When I had the problem I found that although others had mentioned it there didn't seem to be anyone saying that there was a manufacturing issue. However Beta did give me a hefty discount and were, as usually, very helpful.

If you are going to the trouble of changing the gearbox there may be some value in also changing the drive plate, but at 400h it should still be OK.

On the earlier engines Beta had ground an extra chamfer on the gearbox shaft, so when I put the new one in without grinding the extra chamfer the crank lost all end float. So do make sure that when the gearbox is fitted there is still some end float otherwise the crank shaft can lock up. Probably check the chamfer on the shafts of the old and new gearboxes.

Finally, when I pulled the box apart I couldn't get some of the nuts undone so I would imagine repair would be difficult.

Anyway sorry to hear about your problem and certainly speak to the engine manufacturer.

Andy
 
When i had problems with a PRM gearbox on a Betamarine engine I found Lancing Marine very helpful. It was actually cheaper to replace than to repair.

It might be worthwhile to have a look at the PRM120 which is somewhat more substantial unit than the TMC, and is almost a 'plug n' play' replacement'
 
Thanks gents for the advice. I took the boat out this weekend and only had minor slippage when the gearbox was cold, otherwise performed well. I will have a look at the PRM and see what is most reliable. Given the covid 19, we are using the boat a lot and would rather not be stuck somewhere with only reverse working :)
 
noswellplease said:
The TMC40m gearbox came with my new beata 25hp engine some 18 months ago and for some strange reason the gearbox is now faulty and difficult to find the forward gear, reverse is no problem. The original installer is somewhat mystified as only 100 hours on engine. I always felt the unit made excessive noise when above 2,000 revs and the boat seemed reluctant to improve on 5kts. It seems that the drive shaft is now slipping as the mechanic could stop it rotating by just grasping it with his hand so perhaps this has been a problem all along and has been getting steadily worse. Anyway just wondering if anyone else had any similar problems with TMC40M gearbox and what the outcome was? thanks Russ
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Hello my friend,

I have the exact same problem on my Beta 30 with TMC40 transmission. My problem came alive after only 500 hours and while I was sailing around Sicily from Malta. I can assure you it's not the cables but it is a defective gearbox. This problem seems common on TMC40

While I was sailing around Sicily during the last weeks, I noticed that the engine is slightly revving up (100rpm or so) without me touching the throttle, and I could see the rev counter playing and also hearing the engine revving up. The gearbox engages and disengages or slips, so it revs up when disengaged and then back to preset revs when engaged. And I confirmed this problem because when I entered Palermo marina with reverse to park, then the forward didn't engage in order to stop the boat from bumping into the dock. The problem only occurs when the gearbox oil is hot and on forward only. Once in Palermo, I checked that the throttle cables and linkages are still in place. I also checked the gearbox oil and it was on max and reddish on the dipstick, however when I changed it, it was pitch black. Please note that I change the gearbox oil every year according to the manual, and I use Automatic Transmission Fluid (ATF) 0.2 litres precisely. The problem was that I was in Palermo and needed to return to Malta. What I did was changing the gearbox oil in every marina I stopped, and each time I changed it, it was always pitch black, even after 4 hours of working.

The gearbox failed me completely and I felt so frustrated that all went well but I had to return to Malta due to the transmission. One time the gearbox stopped completely in the middle of the sea and didn't want to engage at all. Thank God the sea was calm so I had the chance of changing the oil again. Then it works fine until the oil loses its properties and becomes like water without any viscosity.

And now that I know that the gearbox is slipping, I think it was defective from day one cos I always heared a little whistle noise between 1300-1800rpm and I always thought it was coming from the shaft bellow or vibrations cos it always moved forward without problems and never slipped or revved up until lately. Never occured to me that I might have problems with the gearbox, never!
 
This is the oil after few hours of working ... pitch black
 

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I am having this issue..... I have a new TRM40 gearbox ready and waiting to be fitted. Before I start im trying to do my homework for the installation process for removing the old gearbox and fitting the new one. my engine is a Beta Marine 20HP and its on a Halcyon 27.

Can anyone point me in the direction of some step by step guide to this? do I have to remove the entire engine or can I disconnect the shaft and slide it back? how do I access the 6 Bolts to disconnect the gearbox? Its quite tight to see never mind undoing any bolts!

any help much appreciated
 
Bad news I'm afraid.

On the BD722 the gearbox is bolted to the bell housing and this needs to come off the back of the engine complete with gearbox. This will almost certainly be an engine out job, but if you have space the engine can be swung forward into the saloon to work on it there. Often this can be done using a support across the hatch and a block and tackle.

Once the engine is out it is a simple job, but look at my earlier post about the drive plate and particularly the extra chamfer on the gearbox splines. It should take about 6h to do the job unless you hit something unexpected.

There are surprisingly few attachments on the engine, and if possible leave the mounts on the engine as it makes alignment a bit easier when the engine goes back.
 
We had this problem when the gearbox is cold, for 3 years.
It take about 30 sec slipping befor front gear hooks in, then there is no problem.
When we have drive a while, gear works fine.
Last weekend I changed oil twice same day for an expriment, but after that i will take up to 2 minutes for the gear to pop in.
I removed the wire from the gearbox and pushed really hard with my hand, and the front gear pops in nice.
Problem is inside the gearbox.
Did an expriment and remove the oil and filled in 4dl diesel.
Front and revese gear work perfekt with diesel :)

I cleaned it up and put som fresh AFT oil in, then it worked pretty well.
But today when it was cold it was back at the 30sec delay.

Did an turn with the diesel again and this time I run it a little bit longer.
I also lower the engins idle rpm a little bit.
Filled the gerbox with 2dl Dextron III F raceoil and todays testings where fine.
Tomorrow I will try it when it´s cold.

Engine and gearbox was new 2009 and don´t have extreme lots of hours.

Suggestions and thaughts ?
 
On the Beta Engines Facebook page there was a potential solution for this problem.

Apparently there was a technical bulletin issued in 2014 that gave some advice on how to set up the clearance for the cone clutch. Basically with the gearbox in neutral you slacken off the nut on the selector shaft. You then screw the allen bolt in until you are unable to rotate the output shaft. Then back the bolt off 3/4 turn and lock the nut back up.
The person posting this found it was a bit of a trial and error to get the bolt setting correct, but apparently it fixed the problem and it has been good for 100h since.

Sorry this is all second hand but if you speak to Beta I am sure they will share what they know about this procedure with you.
 
eddystone said:
Is this stuff all specific to the TMC 40? From memory my 2018 Beta 30 has a TMC60 a (?)
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The information is in TMC Technical Bulletin 019/2014.
It appears to cover the TMC 40, TMC 60 and 260 gearboxes.

However, I would speak to Beta before adjusting anything.
 
Apologies for reviving such an old thread. The information here on adjusting the cone clutch was extremely helpful. I managed to track down the TMC Technical Bulletin 019/2014 and just now created an account to include it here for anyone else struggling with this transmission.
 

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Yes, my TMC40P transmission is slipping. The adjustment did make a difference. I'm currently in the process of determining if the transmission is "fixed" or not and will report back in a week or two.

The longer story....

This transmission was installed by a previous owner in 2017 on my Catalina 28 and has about 500 hours on it. The engine is a Universal M25XPB This is the second time it has shown signs of slipping. A few months ago it began slipping very subtly. A very brief and small increase in RPMs and slight change in engine tone occuring 3-4 times a minute. The problem was tracked down to forward gear not fully engaging. This was addressed and it has since run for another 50 hours.

However just a few days ago it began slipping very badly. As in "consider calling for a tow" badly! At the time I was some distance from home. I recalled a reference to the gear lever adjustment procedure mentioned in this thread. I didn't have the full procedure at hand. So in desperation I simply tightened the adjustment screw (#36 in the bulletin) 1/4 turn. This magically reduced or even eliminated the slippage enough for me to get home at low rpms. I've only performed limited testing so far while I determine next steps.

I've been told by multiple sources to simply replace the transmission since a rebuild will come close the cost of replacement.
 
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