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Discussion Starter #1 (Edited)
Hello
I have a Volvo penta MD11 D from 1979, im almost shure the gearboks is the MSB type. but it only says MS and X stamped on the plate.
My question concerning a problem regarding selection/shift from FWD to neutral.
The prop spins fine in FWD and REV, the problem starts when i try to shift from FWD to neutral, or have want to shift to REV. It will not go to neutral when the lever is in Neutral position, but if i move the lever a bit to REV it will.
There is no problem the other way around, from REV to neutral it works perfect. sometimes when i have try to go from FWD to Neutral i jumps direct to REV, because I have to move the lever to much toward REV before it goes neutral and the lever is very hard to move. So i checked the oil level and added some volvo gear oil, not ordinary engine oil as i read in the manual, the Volvo dealer was telling me that the gear oil was the right product..
Anyways the oil did not help and i thourgt maby the idle was a little to high, so i adjusted it to 750 RPM, It did not help!.
The selecter arm on the gearbox of moving correct in ways of position.
Does anyone here have any advices how to fix this.
I have read that MS gearboxes have some shimes under the selectorarmplate, would it help to remove 1 or 2 shims. And For operating "Forward" and "Reverse" the Volvo Penta patented cone clutch can be worned..

Im from Denmark, hope you can read my english :)
Best regards Christian
 

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Discussion Starter #3
Thanks Dabnis
I Think the cable is ok because it moves the lever on the transmission box. I meen if i put the controllever to netrual/idle the gearbox-arm is positioned at 3 O-clock and if i move it toward fwd or rev it just moves from 1 and 4 0-clock.. So the distance of movement is the same, for each site of neutral position. The thing is, when in REV and moved in to neutral, the gearboks arm is positioned
At 3 o-clock when it changes to neutral. But when changen from fwd to neutral the gearbox- arm have to be moved more in to REV, " over the neutral 3 o-clock" point before it changes to neutral... Sometimes it jumpes directly in REV
 

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I can't find it at the moment, but there is a reported fix if you search the forums. MD7a's suffer from this as well. What happens is there is a shift fork that rides in flat bottom V groove. As it wears, the shift fork starts to put pressure on the flat bottom of the groove and less pressure on the side of the groove where it should. The repair procedure, if you want to milk a few years out of it before buying new parts, is grind perhaps a mm off of the bottom of the fork, keeping the perhaps 50mm radius, so it doesn't ride on the bottom of the groove anymore. My MD7a suffered from this. I took it apart and observed the wear pattern, but sold the transmission for parts, so never tried the fix. I've never quite figured out photos on this forum, but if you want, I can send you a photo of the 7a fork via email.
 

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Discussion Starter #5 (Edited)
Hey Shogan50

It sounds like that could be the problem!, do you mean that the wear is causing the shift-fork to move down, so it starts to lay pressure in the bottom of the groove? I will try to deassembly the gearbox so i can inspect the shift-fork. I could be very helpfull if I could see your photo of the fork, please E-mail if your have the time:)

regarding the repported fix, do you remember where the thread is located.. some keywords/forum or something,
I will try to look it up..

Thanks Christian
 

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Discussion Starter #7
Dear Shohan
thanks a lot, for your help.
It is an invaluable help, no one in Denmark knows anything about it or they are hard to find:) I will start to deassembly and take a look..
 
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