Gentlemen, I've got what I think is a quick and easy question. Backstory - tore apart ST-300 over a year ago to rebuild. Sat for 1 year. Slept a few hundred times since tear down. But, trying to put humpty dumpty back together again. So, want to see if those of you who know better than I do can clear this up for me. Resealed the servo assembly. This particular unit has a directional seal. Pretty sure I have it oriented correctly, but please view attached photos and clarify. I'd like to avoid any surprises after she's all reassembled. Ha In the second photo, you can see how it'll fit down into the bore on the transmission case. Appreciate your insight!
Hi, Mark. Thanks for the reply. Can you clarify - the orientation in the photo is incorrect and it should be reversed.
Can you take a pic of it a bit further away so I can see exactly where that part goes? Im guessing, the spring goes "into" the oil, yes? If so, the seal's lip looks backwards. Do you have a chassis service manual you could reference?
Unfortunately, the original manual which I used for the rebuild does not have a photo or any specific details to reference that I can find. I also referenced a how-to post on this forum from member "Kirk". It also doesn't have any details or a good photo to reference. Yes, I would say that the spring goes into the oil. You can see in the photo, the piston, the spring and then the rod protruding, which engages the band strut. And then there's a cap with a simple O ring (and retainer) which closes it into the transmission housing.
Double post. But this is the best image I can produce, from Kirk's how-to. Coincidentally, it appears to be oriented in the same manner as presented in my photo. Which further unsettles the matter. Lol
I'm looking at the 1967 Buick Chassis Manual. They have a detailed section on the ST300. Is this the secondary piston seal? The cover seal looks like an O ring. I think if that seal is on wrong, it should be very obvious when you push that piston into it's bore that it is wrong, the seal will bind or distort I would think.
Okay, I'm sorry. I DO have those photos in my copy of the manual. It's still not super clear to me, glancing at the image. But I would say that it appears that my orientation (in the OP) is reversed, based on the images in the manual. And yes, this is the secondary piston seal. It's the "lip" or more like a wiper that has be confused. But here's the deal. I pressed the piston into its bore with the seal BOTH ways and I definitely felt it "bind" the way opposite of my photo in the OP. So I thought, no way this is right. No way this thing can stroke smoothly like this. That's why I ultimately reversed it to the orientation in the OP photo and went ahead and installed it that way. So, again, now further confused, because it definitely appears in manual image 74-171 that the wiper faces downward, or "faces the oil," as Mark suggested. I have attached the only other images I have.
There's always a reduced diameter step and that dictates the direction that the lip of the lip seal should face. If you put the seal on backwards and installed it and it was binding - you will need to carefully check to make certain the seal has not been damaged. It's good practice to inspect the new seals for damage, as, I had a new seal that had a tiny split on the lip.
Hi, Matt. Okay, I see what you mean about the "stepped" diameter. The way I have it configured has the lip resting upon the stepped down diameter. And where the piston enters the bore it is flared, but diameter immediately reduces to accommodate the seal. So, in that sense I would say my orientation is correct. As far as inspection, I did give it a good look over and felt comfortable enough to reuse. It was well oiled when I applied it to the bore and that seems to have been my saving grace. I attached a photo I stole from an ebay add. You can see where the diameter is tapered and certainly makes sense that that is where the lip would rest.
I just checked with Mark Deconti and you have the seal on correctly as pictured in your 1st post. I sent him that picture.
That's great. Thanks, Larry. I appreciate you all very much. Hopefully we've left enough detail here if there's another knucklehead like me somewhere down the line that loses his marbles.
