Alpha I gen II pressure test - Shift Shaft Seal

[Strecker25]

Short backstory...I have twin AlphaIGenII's on a 290 sundancer. OEM uppers, SEI lowers. We blew the lower gear set out the side of the drive on our stbd side. SEI replaced it under warranty, all seemed well..

We put 10 hours on the new lower and I would notice a very small drop in gear lube level during some trips. I attributed it to air finding its way out and we were close to the end of the season anyway. I would also often see a very faint sheen on the water at the slip.

I have the drives home now and pressure tested them. They both hold 10psi for 24 hours with no issue. If I turn the shift shaft and put any amount of pressure in either direction (FWD or Reverse) I have a leak. This is the case on both of the units, including the one that was not losing lube. I can also pull up on the shaft i would guess a little less than 1/4" but again, same on both units.

From the diagrams it looks like it is simply a large Oring style gasket, so it makes sense that pressing it in any direction would cause air to leak out. I would say that "normal" movement of the shaft doesn't cause a leak, but how much pressure does the shift shaft get put under during operation?

Is this normal, or should the shift shaft keep a tight seal no matter how much you push or pull it? I don't want to RMA the drive again if it is fine.

Thanks! sorry for the long winded question

 

[Bt Doctur]

On the gen II drive the shift shaft seal itself is replaceable, the plastic housing shift shaft housing it sealed by a O ring and 2 bolts seal is 26-80236 or Sierra 18- 2009

 

[Strecker25]

I did see that, and the replacement looks relatively straight forward as long as the drive isn't moved while the shaft is out But, would you expect there to be no leak no matter if the shaft is pressed in either direction? I could do video of what is happening, but I don't know that it will help show my point

 

[Bt Doctur]

If its leaking between the seal and the shaft , it needs replacing. Have done quite a few. Work slowly and carefully . have the drive vertical when removing the shaft with the plastic housing. Next remove the washer and hairpin clip ,them remove the shaft and R&R the seal

 

[Bt Doctur]

 

[Strecker25]

Thanks, so I took a video of the "good" drive. This is the one that didn't appear to be leaking lube, but the symptoms on the bench are pretty much the same on both sides concerning this leak. You can see in the beginning I am just shifting it, but at the end with just a little thumb pressure the bubbles start. Let me know if you think this needs a R&R. Because the drives are under SEI warranty, I'm probably going to have to ship it to them to keep the warranty coverage.

https://www.youtube.com/watch?v=NV8tMQn1azs

 

[Strecker25]

SEI offered up two new bushing assemblies, so I'll be doing the repair. Justin from SEI said the same thing, work slow and careful but there is not much to it.

 

[Strecker25]

Just an update, the new bushings came in and they seal properly now. No leaks with pressure in any direction. The repair was eas, 5 minutes each drive.

 

[Rick Stephens]

Good deal. Once you've done one, you;ll never worry about it again. Easy enough and cheap enough to replace whenever you do the impeller.

 

[Strecker25]

Absolutely, I was surprised to see both of them have a small leak only two years into service (about 100 hours) but like you said, cheap and easy so worth doing every year or two.