Mercury Mark 28a Auto transmission

[Mark Bartlett]

Does any body on the west coast up on 28a auto trans I have all the special tools to work on it the book is very vague on working on one I have an issue on one that keeps messing up the springs Thanks Mark

[david-bartlett]

MRB,

Check out http://www.johnsoldmercurysite.com

Lots of info on the auto tranny motors there. You will probably have to join for full access but worth it.

[mercuryman]

Look for post by DaytonaJohn he seems to be the expert

[billw]

If you keep messing up the big spring, (gets pulled in and bent, between the two drums) it is probably not shimmed right and/or there is a thrust washer missing.

Long live American manufacturing!

[dockbuster1]

make shure the ball bearing is not loose they didn’t last long and when they get loose even a properly shimmed trunion will separate

[garry-in-michigan]

John brought a cut-away of that transmission to several meets and gave demonstrations on its assembly and adjustments. I thought it was ingenious and likely to last longer than the dog clutch mechanism used by others. It is definitely more expensive to build and harder to service, but isn’t that why people buy Mercuries?
The pictures I took are no longer accessible. . . 😥

[dave-bernard]

they are not that hard to work on BUT take a lot more time.

[billw]

quote Callie30R:

make sure the ball bearing is not loose they didn’t last long and when they get loose even a properly shimmed trunion will separate

This is a very good point, too. I have seen that a lot, as well as the missing thrust washer. You can still get those bearings new, from a bearing supply house and they’re not too much money. In the transmission, there is a basically a big, tall, stack of parts, going all the way up to the top of the water pump. All the parts must be there, be in good condition and the left hand nut be properly tightened. Then the whole thing is taken into consideration with a special Mercury shim tool and shims are added or subtracted, to give proper end play. Anything in the stack that allows too much end play will allow the big coil spring to slip in between the two drums and be ruined.

Long live American manufacturing!

[Author]

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