Shift Shaft pops out when pressure test is done.

[ChrisSmith290]

Hi , I have an alpha one gen 1 1988. As soon as I put air in the drive the pressure moves the shift shaft to the side out of gear. I replaced the shift shaft bearing and it's still happening. I can try to move the shift shaft in forward gear but it's under pressure and just pops right out again. Can anybody tell me why this is happening. I have twin 4.3's and the other drive is perfect, the shift shaft on that drive has no pressure on it. Thanks in advance for any feedback.

 

[Bt Doctur]

the shift shaft is not affected by pressure in the drive?
exactly what work was performed on this drive.

 

[ChrisSmith290]

Both drives ran great all year. When I took the drives off for the winter I noticed small amount of gear oil (about 3 ounces ) in the bellows. I replaced small yokes and oil seal in yoke assembly and water pumps which I do every year. First drive perfect no issues holds pressure. Second drive was losing pressure and moving shift shaft to side. I replaced shift shaft bushing and now it holds pressure but shift shaft still is under air pressure. It will not stay in forward gear when I pump air into it. (12 psi )

 

[Mercruiser420]

Is still leaking oil after you replaced all those seals/bushings?

 

[ChrisSmith290]

No it's definitely not leaking where I replaced the oil seal and yoke . After I replaced the shift shaft bushing it probably will not leak oil because I pumped 12 psi in yesterday afternoon and it's 11.5 psi now after turning the gears periodically. I doubt that's enough to cause any leak in oil. I'm trying to figure out why there is constant pressure on the shift shaft that takes it out of forward gear the instant I start pumping air into the drive. BTW before I changed the shift shaft bushing the psI would dwindle down to zero overnight so I'm on the right track.

 

[alldodge]

Not an alpha expert but have a thought; I would figure the drive would try to stay in neutral from the spring in the shift spool. Have pressured test many drives but never bothered with trying to keep the drive in gear, would rotate prop shaft separate from drive. Wonder if your other one is hanging, cannot say

Look forward to hearing from the experts

Edit: correction, the shaft comes out. With it coming out is the C-clip in place?

 

[alldodge]

This one

 

[Bt Doctur]

Still cant figure out what is happening. no amount of air pressure would operate the shift mechanism.
AllDodge, only some outboards have a spring detent, the merc I/O doesent
How could the shift shaft rotate with air pressure.

 

[alldodge]

BT what caused me to come back and edit was the OP said the shaft is being pushed out. This lead me to think not so much it's going out of gear but that the air pressure is pushing the shaft up, and the only way I can imagine that this could happen is if the c-clip is not there, or something else on the shaft is causing this.

 

[Bt Doctur]

Knowing how the shift sits there I have never had the shaft even move when pressure testing a drive.If the O ring was at the bottom of the shaft and the cavity was sealed, maybe it could push the rod upwards. Air presure raising the SS shaft up and out, dont think so.
Plus he says the shaft turns with pressure?????????
As soon as I put air in the drive the pressure moves the shift shaft to the side out of gear.

 

[ChrisSmith290]

Exactly correct guys! I have never seen this before and this is NOT my first rodeo with Alpha Drives. The drive does not appear to be leaking. I replaced all uppers today. Shift shaft bushing yesterday, small yoke and oil seal on yoke assembly few days ago. I've sprayed soappy water everywhere, no bubbles! You are correct in saying the shift shaft should not move when air is put in the drive but it does. When I do a pressure test I put the shift shaft in forward gear and turn the prop shaft counterclockwise. As soon as I put air in I watch the shift shaft turn counterclockwise just out of gear. It feels like its spring loaded when I try to push it back. It will not stay. Again the drive does not appear to be leaking. Its been 6 hours since and the gauge hasn't budged . I'm stumped!

 

[Bt Doctur]

With no pressure you can move the shift shoe fully CCW to CW?And with air pressure the shift shoe moves CCW all by itself?
is the drive positioned perfectly vertical?

 

[ChrisSmith290]

Yes it's on a stand. It's level,

 

[flipbro]

Is there oil in the drive while you pressure test it?

 

[ChrisSmith290]

Just air 12 psi that holds

 

[ChrisSmith290]

I'm just as stumped as everyone else is. One thing for sure is when I finally find out what happened I will be writing another post here to let you guys know what it was. I want to thank everyone for their input.

 

[ChrisSmith290]

No oil in drive

 

[Mercruiser420]

Sounds like the clutch dog moves to one end (reverse) under air pressure.

 

[JustJason]

A movie is worth 1000 words. Take a video of what you are doing and observing and pop it upon youtube.

 

[ChrisSmith290]

I more confused than ever. I replaced the seals and o rings, took everything out except pressed on gears in lower unit. Put everything back, new shift shaft bushing, water pump base with seals etc. I kept the drive separated and plugged the oil seal hole in the lower. I put the drive in forward gear by turning shift shaft clockwise and prop shaft CCW to lock it in place. With the drive separated I watched the shift shaft move CCW out of gear the moment I started pumping air into the lower. The drive does NOT leak anywhere. It will hold pressure . I have no possible solution to why this is happening. There has to be someone out there that had this happen to them.