Volvo MSB gearbox - sticking in gear

[Guest]

Hello!

I have a problem with the Volvo MSB gearbox in my boat. With the engine idling the gears seem not to engage properly and the shaft turns very slow. When increasing the engine speed drive is taken up as it should be. The problem comes when trying to disengage the gear. With the lever on the gearbox in neutral the box keeps driving the shaft. The gear can be disengaged by pushing the lever a bit into the reverse position and then back to neutral (and vice versa when in reverse). The box has been filled with ATF oil but I have changed to engine oil as specified by Volvo.

Does anybody know what to do?

Best regards

 

[Guest]

Adjust your cables quick.

Before the clutches wear out due to partial engagement.

 

[Guest]

Re: Adjust your cables quick.

Thank you for your reply. I have already decided to replace the cables, as they seem to be far beyond the prime of their life- but maybe it is already to late, as the problem does occur even when I disconnect the cable at the gearbox and move the lever manually.

Many thanks and best regards

 

[Guest]

I have to be a bit careful what I say here, as I'm not too sure which box you have. The first of these boxes was the MSB, but I don't think it said that on the gearbox. I don't think it had anything on the box, but it was known as the MSB. That box had steel clutches, a brass sliding sleeve and a steel sliding shoe. The next box, which was the MSB! and said so on the box had ferodo type lining on the steel cones, a steel sliding sleeve and a brass faced steel sliding shoe. Got that?! The sliding sleeve has a groove in it in which the sliding shoe slides! The is not a straight cut around the sleeve but is a wiggley? groove which acts as a servo and helps the sliding shoe push the sliding sleeve into and out of mesh. If the sliding shoe is not deep enough into the groove you will end up with the problem you have On the top of the gearbox there is a brass selector, you will know what I am talking about if you have disconnected the cables. In the centre of the selector is a steel hex. and under the head are several shims, it will look like one washer because they are all stuck together with goo to stop oil leaking. You could try removing two and only two of these washers and try changing gear with the engine running. BUT BEFORE DOING THIS, CAREFULLY REMOVE THE SQUARE PLATE THOUGH WHICH THE SELECTOR PASSES AND CHECK THE GROOVE AND SLIDE FOR BURRS OR ANY OTHER DAMAGE. GET HELP IF IT DOESN'T LOOK GOOD. NOTE WHICH WAY THE LONGEST 'TOE' ON THE SLIDING SHOE IS POINTING AND FIT IT BACK THE SAME WAY. (longest toe to reverse if I rememberr correctly). Tom

 

[Guest]

Many thanks for your reply Tom. The users manual that came with the boat states that it is an MSB box. I am quite familiar with Technodrive gears but it's my first Volvo. I have had a closer look at the exploded drawings in the spare-parts catalogue and the servo mechanism seems to be about the same. I will do what you suggested and remove the square plate with the selector mechanism and check that everything is ok with the sleeve etc. Chances are high that because of bad adjustment of the cables something is worn in there. If not I will try to remove a washer or two, maybe this will do the trick.

Oh yes, and I will obtain a workshop manual for the box (I've only got one for the engine), in the long term this might pay for itself.

Again, many thanks and best regards

Marcus