Transmission gets stuck in gear or pops from forward to reverse. Volvo MS3C / TAMD40B

[CaptDan2018]

Thanks in advance for any information or insights offered!

The problem is that my MS3C tranny always has a hard time getting into neutral (pops from one direction to the other going right through neutral - especially when cold) and occasionally gets really stuck in gear and requires (panicky) whacking on the controls to get it to shift. It does not slip or have any problems once in gear.


This is happening aboard a 1984 Kha Shing 40ft trawler that is powered with TAMD40b's which seem to run great. There are two different transmissions. Port has been replaced with a ZF 63A 2.68:1. The starboard is (original?) an MS3C 2.73:1

The port engine has been raised with blocks under the engine mounts to accommodate the 8% difference in the output shaft. There is a different coupler too I think.

I'll add here that when the engine is NOT running it shifts smoothly. It also shifts smoothly enough on the transmission itself with the linkage disconnected. However, even when shifting at the transmission it is hard to get it to stop in neutral, maybe even harder than with the gear lever at the helm. But again, when not running it shifts smoothly both at the helm and at the tranny with the linkage disconnected.

(The syncronizer has been disconnected and I am fine adjusting RPM's by ear to get them together while cruising.)

After much reading it seems like the transmission has a worn spot on the shaft on which the gear slides / changes...or something like that. I am also getting the impression that the cost of fixing it will be as high as a new / rebuilt ZF and it isn't a great transmission anyway.

Basically I just want to be able to shift comfortably. I'm comfortable replacing the transmission or taking out the old one and fixing it. If I knew the best course of action I would feel a lot better about it

Any insights offered will be much appreciated!

BTW, I've been sailing for years. I feel comfortable on any sailboat under sail or power. But I am very new to twin engines and trawlers. It is incredibly fun being up on that fly bridge I have to say.

Dan

[CaptDan2018]

Good news for me! I was finally able to replicate the totally stuck problem to a loose screw on the control housing! It has happened three times now and this is the first time I could get it to happen again when I was able to get into the ER.

The popping from forward to reverse (and reverse to forward) without stopping in neutral is still there but I can still use the boat

The long term question is still the same though - should I be getting prepared to replace that transmission and if so thoughts about converting to ZF so they are both the same?