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Question on resealing an 280 DP-PT

Walleye4Days

Contributing Member
I have pulled my drive today (280 duoprop with power trim) and am planning on resealing it as I found the gear oil to be a little milky. I believe it was leaking through the upper unit because the drive bellow had a tear in it and a decent amount of water was in it when I pulled the drive.

But, do I really need to strip down the entire drive to every little nut and bolt to do a reseal (its butter smooth and operates flawlessly still)? Or, are there just a few key places I should reseal to keep water out of the drive?

Thanks in advance for anyone who takes the time to help me figure this out.
 
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I have pulled my drive today (280 duoprop with power trim) and am planning on resealing it as I found the gear oil to be a little milky. I believe it was leaking through the upper unit because the drive bellow had a tear in it and a decent amount of water was in it when I pulled the drive.
Here's what happens when the drive shaft bellows allow water to enter.
The seal surface washer is carbon steel.
Water will cause rust on this washer's sealing surface.
As the rust becomes abrasive, it eats away at the seal.
The seal eventually fails.
As the drive warms up, mild pressure forces the oil past the seal and into the bellows area.
As the drive cools back down, Negative pressure pulls a small amount water back in past the seal.
This cycle continues.


But, do I really need to strip down the entire drive to every little nut and bolt to do a reseal
That would depend on how well do you wish to preserve this drive?


(its butter smooth and operates flawlessly still)?
Yes, understood.

Or, are there just a few key places I should reseal to keep water out of the drive?
With the GL-5 gear lube completely drained, you will want to perform a pressure and vacuum leak-down-test.
This is a test that requires the drive to hold pressure and vacuum for a duration of time.... that is why it's called a "leak-down-test".
Common and most frequent areas of concern:
Shift mechanism eccentric piston seal. Do not do this until you have read up on it.
Prop shaft seals. You'll need to build yourself a copy of my prop shaft bearing carrier puller tool.
O-ring seals at dip stick and drain plug.
Gasket seal at gear oil fill plug.

Thanks in advance for anyone who takes the time to help me figure this out.
 
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Thank you so much for the advice and info. I think I'm gonna go ahead and redo most of the drive. I've watched a ton of videos, read a ton of your answers to other people's issues and questions regarding the very thing I'm getting ready to jump into.

I've done plenty of mercruiser from A to Z in the alpha and pre alpha area. But, these VP's are whole other animals with engineering out of this world haha. I was extremely surprised this drove with around 1m hours in it and over 35yrs old with not the best maintenance and upkeep by the previous owner, was still so insanely butter smooth in function and shift-wise. My alpha ol would've been destroyed ten times over if same history Haha.
 
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Thank you so much for the advice and info.
You are most welcome!

I think I'm gonna go ahead and redo most of the drive. I've watched a ton of videos, read a ton of your answers to other people's issues and questions regarding the very thing I'm getting ready to jump into.

I've done plenty of mercruiser from A to Z in the alpha and pre alpha area. But, these VP's are whole other animals with engineering out of this world.
I agree...... the engineering is superior.

I was extremely surprised this drove with around 1m hours in it and over 35yrs old with not the best maintenance and upkeep by the previous owner, was still so insanely butter smooth in function and shift-wise.
In order kill an AQ series drive, one must almost deliberately attempt to destroy it.
Keep the gear oil clean and full (30W for the s/p, and GL-5 for the DP), change the seals when due, keep up the maintenance on the PDS bearings (or change them), and it will go for another 30 years.

When lubricating the PDS bearings, do so with the engine at idle (dynamic -vs- static).
If the grease cavity had been pre-filled correctly (during the last bearing replacement), it will only require four to five pumps.


Side note:
I once replaced GM V-8 PDS bearings for a customer and found that the PDS cavity was bone dry. Not just lacking grease..... it was bone dry!
The mechanic who had previously replaced them failed to pre-fill the cavity..... and this was a well known marine repair shop here in Portland Oregon.


My alpha ol would've been destroyed ten times over if same history Haha.
Yep!
 
Hahaha, your eyes had to be HUGE when you seen that bone dry pds cavity lol..

So.. I just ran into another problem here on this 280. On the upper gear housing, where the clamp ring thing (the 4 bolt clamp that's holding back the ujoints from slipping right out forward, the part on the drive where the drive bellow clamps to) one of the bolts is INSANELY corroded to the point someone stripped it out that was in this previously alone years back.... I got the other 3 bolts out, but I have NO IDEA what to do about that bolt to get it out. Because, I need to reseal that area behind the ujoints since rust and etc made its way into the bellows and more than likely ate up that seal there... are there any other options for that bolt or a clever way to be able to get the bolt out without destroying that clamping collar/carrier the ujoints are with?
 
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Hahaha, your eyes had to be HUGE when you seen that bone dry pds cavity lol..
Well, it was not the first time I had seen this, otherwise yes...... I would have been wide-eyed!

S
o.. I just ran into another problem here on this 280. On the upper gear housing, where the clamp ring thing (the 4 bolt clamp that's holding back the ujoints from slipping right out forward, the part on the drive where the drive bellow clamps to) one of the bolts is INSANELY corroded to the point someone stripped it out that was in this previously alone years back.... I got the other 3 bolts out, but I have NO IDEA what to do about that bolt to get it out.
That too is not the first time that I've dealt with that.
I can share with you what to do next.


Because, I need to reseal that area behind the ujoints since rust and etc made its way into the bellows and more than likely ate up that seal there... are there any other options for that bolt or a clever way to be able to get the bolt out without destroying that clamping collar/carrier the ujoints are with?


OK, up until the first A series transmissions, all of the front collar bolts are wet area threads.
These bolt threads become corroded, therefor making it difficult to remove them.
Most DIYrs do not use heat on the thread insert areas, and they end up stripping out the hex head sockets.

You will need to:
Remove the top cover.
Remove the eccentric piston housing.
Find a machinist who is good with a milling machine.
He will clamp the transmission to his milling machine with the eccentric piston side down.
He will gently go in with a cutter, and remove most of the remaining bolt fragment.

NOTE: there is a very delicate shoulder in the bolt bore that must not be disturbed.
This surface is what the sealing washer seals against.
If this shoulder is disturbed, you will end up purchasing a new clamping collar, and will then need to go through the shimming process.

He will then cut the remaining portion of the bolt away, but not all of the bolt.
You will need at least 5/8" of bolt shank left for later extraction.


With the other three bolts removed, and with most of the one bolt removed, you can now carefully remove the collar and the bearing box.

You will next heat the gear case at the area of the thread insert (Propane heat only....... no Oxy-Acet) and remove the remaining portion of the bad bolt.


Here is a picture of my machinist doing this very same thing for me.

I've had him do this many times due to DIYrs rounding out the hex sockets. On one occasion, I had to do this because of my own failure to remove a stubborn bolt.
 

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Perfect, I got it! ....Kinda...

I ended up putting it on my drill press/milling press, and I drilled out jussssst the head of the bolt. The clamping collar came right off the box and viola'!

I just used vice grips to remove the post of the bolt that was drilled out.

Something I'm confused on though, is you mentioned a sealing washer and the shoulder of the clamping collar. I don't have any washers on the 4 bolts that clamp the collar back onto the bearing box. Just the bolt heads (Allen bolts) that fit very nicely within the holes of the clamping collar.
 
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Perfect, I got it! ....Kinda...

I ended up putting it on my drill press/milling press, and I drilled out jussssst the head of the bolt. The clamping collar came right off the box and viola'!
Given the critical shoulders within the bolt bore, I would have not used a drill press.
I am glad that you were successful.


I just used vice grips to remove the post of the bolt that was drilled out.
Yep..... that will work!

Something I'm confused on though, is you mentioned a sealing washer and the shoulder of the clamping collar. I don't have any washers on the 4 bolts that clamp the collar back onto the bearing box.
The four bolts thread into the main gear case, and then via the clamping collar, they squeeze and secure the bearing box in the main gear case.

Just the bolt heads (Allen bolts) that fit very nicely within the holes of the clamping collar.
Yes, I mentioned four sealing washers and four delicate aluminum shoulders within the clamping collar.

Look at the exploded view of the 280 transmission, and look at SEQ # 37.
http://www.marinepartseurope.com/en/volvo-penta-explodedview-7744020-44-17973.aspx

This washer not only offers hex head friction relief (against the aluminum shoulder), it is also a sealing washer against water intrusion from the wet area bolt threads.
I would not re-assemble without them!
 
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