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View Full Version : Transmission Gurus Needed


hz900
04-02-2010, 04:38 PM
In reference to this thread

http://www.mastercraft.com/teamtalk/showthread.php?t=34561

So I just rebuilt the transmission myself, first transmission I have done. I've got it installed and the engine running good after some other fixes and I have a problem. The transmission is always engaged. So this is partially a good thing that it does turn, however when I crank the boat in neutral the trans is engaged forward. I've tried unhooking the cable from the shift lever and moving it by hand but nothing happens, just keeps turning in the same direction. I don't have the shaft hooked up yet. Anyone got any ideas what the cause could be?

JLeuck64
04-02-2010, 05:26 PM
Hmmm... sounds like you have a clutch pack binding or the clearances between the discs and plates is not great enough. Anyway I would not hesitate to pull the trans out again and disassemble to inspect your previous work. Bummer I know, but the only way to fix it I am afraid.

My only experience with a boat trans is my own with one of those AF Hurth marine trans but they are essentially the same as a Borg Warner. When I had to go through mine I used compressed air pressure to check the operation of the forward and reverse clutch packs before I installed the tranmission back into the boat. When the trans is assembled you should be able to spin the input shaft by hand and the output shaft will not spin, that's neutral. If you look around carefully at the top of the trans where the shift cable connects you should see the valve assembly that directs fluid inside the trans. Even closer inspection should reveal some plugs that can be used for pressure testing a running transmission. On my trans I removed one of those plugs and used a rubber tipped blow gun to apply compressed air into the test port. By moving the shifter into forward and the reverse positions you can direct that compressed air to apply both the forward and reverse clutch packs. Turning the input shaft while applying the forward clutch pack should result with the output shaft turning. Then shift the trans into reverse and apply compressed air again while turning the input shaft. You should see the output shaft turn in the opposite direction. Of course you would expect to see neutral return after performing both of these air tests of the clutch packs....

If all is good after performing this check you can feel confident about re-installing your trans to the back of the engine and firing it up.

CantRepeat
04-02-2010, 06:25 PM
There are some clearance involve with the clutch packs as posted. During dry assembly you should have check that clearance and adjusted it with different thickness of snap rings that hold the clutch packs in. If you are getting forward movement while in neutral, after you made sure it was in neutral by moving the shift lever by hand, then it has to be the clearance is off.

One thing to note, some new model clutches are thicker then older ones. When I rebuilt my 71 it was stated to leave out one friction and one steel disc in the assembly. I still did the gauge check on it.

CantRepeat
04-02-2010, 06:27 PM
Also here is a link to the service manuals I used.

http://www.mastercraft.com/teamtalk/showthread.php?t=32581

hz900
04-02-2010, 06:44 PM
Well thats a bummer. It really sounds like the clutch packs are the issue. I just talked to a friend of mine that works at a auto and boat repair shop and he said the same thing. Oh well its a good lesson, although a painful one because the trans is a pita to get out and in IMO. I was unaware of the newer clutches being thicker than the older ones, and I didn't clearance them like I should have. I removed and then reinstalled the new in reverse order. Per visual inspection nothing seemed to be binding or to tight. Now I know.

92Maristar
How did you go about taking the transmission out? I undid the long bolts on each mount and the bell housing to block bolts and pulled it out. Is this the preferred way or is there an easier I am not seeing?

Cloaked
04-02-2010, 07:41 PM
Well thats a bummer. It really sounds like the clutch packs are the issue. I just talked to a friend of mine that works at a auto and boat repair shop and he said the same thing. Oh well its a good lesson, although a painful one because the trans is a pita to get out and in IMO. I was unaware of the newer clutches being thicker than the older ones, and I didn't clearance them like I should have. I removed and then reinstalled the new in reverse order. Per visual inspection nothing seemed to be binding or to tight. Now I know.

92Maristar
How did you go about taking the transmission out? I undid the long bolts on each mount and the bell housing to block bolts and pulled it out. Is this the preferred way or is there an easier I am not seeing?If you do this again, please consider doing a pictorial at intervals or steps to enhance the project. I'd like to see the entire rebuild with pics.

Thanks if you do.

CantRepeat
04-02-2010, 08:07 PM
Not the best methode but what I did was put 2x4s cut to length and put them under the exhaust to hold the motor up. More over I use a hoist to lift the motor up and then put the 2x4s under the exhaust and lowered the motor onto them. This freed the transmission up.

I'll look through my photos for the transmission rebuild photos as I did take a tone of them while doing the rebuild. If I find them I'll post them somewhere else and link it here as this forum only allows for 4 or 5 photos per post.

I'll also look for the exact info on the snap ring thickness for you.