71C Velvet Drive Trans

[Classic Trade]

I have a 1977 28' Bertram with 71C Velvet Drive transmissions. One of the transmissions is leaking trans oil in the rear of the trans. My question is can I replace the oil seal in the bearing retainer at the output end of the transmission without removing the entire transmission from the boat? If so, how is the best way to do this?

Classic Trade

[Bruce]

Yes you can if you have the space.
The couplings have to come apart, push shaft back, remove nut inside of gear output flange(1.5" I think off hand).
Once nut is off, coupling should come off splined shaft. if not a puller is needed.
Replace seal.

On the reduction gear drives there is a crush spacer that should be replaced. It keeps tension on the flange so that the coupling does not go too far into the back of the gear and ride the lip seal up into the back of the flange rendering the seal useless.

If you be careful you can get away with not replacing it. As you tighten the nut feel for when the coupler comes in contact with the sleeve and just snug past that point.
Use a NEW nut as they are nylon inserted and once you remove the nut the old insert is shot.

Use sealer on the gear output flange before sliding back onto shaft, if not you can get tranny oil leaking into the bilge.

BTW, when you have the gear flange off look for a groove in the surface the seal rides on, replace if there is one.
Polish up the seal surface with some 800 wet paper.

[Hyena Love]

But, be aware that the nut on the back of that tranny might be on there real tight. As in, break the tool tight. Been there. Tried that. Only had manual tools though. Eventually, gave up after breaking the tool and pulled the back half of the tranny.

Second suggestion might be to avoid the temptation to crack open the pumpkin in the boat thinking you can just remove the rear half of the tranny. Now, that approach can work, but getting those gears/splines to slide back together can be a frustrating job while laying there on the deck. Bet we spent 3 to 4 hours on just that task.

[Classic Trade]

Thank you both for the information. I really appreciate it.

Classic Trade.

[Bottom Line]

I appreciate I'm reviving an old post but I'm about to tackle replacing the rear seal on a 72C and have a question for Bruce or anybody else which I thought might add to the topic for anybody who is searching the site for info. Specifically, when putting back the output shaft what type of sealer should I use and where and how much of it should I apply?
Thanks.
Mike Ford

[Bruce]

When you pull the flange off you'll see splines. Use a gasket type of permatex, gray is good and put a bead around inside in the end of the flange that goes into the gear. As you push the flange on the sealer will travel out to the nut side, not into the gear if the sealer was put onto the shaft. Don't wipe any off and tighten the nut.