AQ 280 Bearing Failure

The mechanic had the outdrive apart and walked me through the failure.

The top nut on the intermediate shaft had come loose and the top two bearings piled up from the filings. The cone clutch and pinion gears in the transmission are a dark colour...he figures the clutch had been slipping. Everything else looks good.

I purchased a complete upper drive...he is taking apart to ensure its all good, and am replacing the rest of the tapered bearings, seals, shims and gaskets. He has the re-shim procedure Riccardo has mentioned.

The question I'm putting out there is: Do you think my modified re-built 350 has too much torque for this drive?

Are you talking about the top nut and washer on the upper verticle shaft? If so I have never seen one of these come loose in 33 years of working on V/P's. The clearance WILL lossen up over time but the nut come loose, NO. The two steel keepers on the other end of the shaft have worked part way thru the brass retainer. There are other parts to replace maginal parts in the upper to accomadate extra HP put to the AQ drive.

I having a bit of trouble with your mechanic's assessment re;

The top nut on the intermediate shaft had come loose and the top two bearings piled up from the filings.

Click to expand...

This nut would contact the top cover and chew up the aluminum if this were the case.


I agree with Gary.
I too have never seen one of these top LH thread nuts come loose..... not when they have been installed and tightened correctly.
More often than not, the issue is with the brass split ring keeper.... aka "wear washer".... expanding.
When these expand, the vertical shaft end play becomes excessive.
Replace this wear washer, and check to make sure that it meets the OEM clearance!


The upper shaft is not an "intermediate" shaft.... this is often refered as the transmission "vertical" shaft.
The three gears are a "main drive" gear.... and two "driven" gears.
There is no pinion gear.... that's an automotive term.

The dark color is likely from water intrusion, and eventual rust.
A sliding sleeve that has been slipping, would certainly offer tell tale signs in other areas.

Are you sure this is a qualified AQ series Volvo Penta expert?
Yes... a tad bit of sarcasm in that, but you can't believe what we see with regard to some of the people pretending to know how to work on the AQ series..... the easiest ones to work on, by the way!

Don't be afraid to ask questions and pick his brain!
If he can't answer your questions, that may say something about his qualifications!
Let's hope that he knows what he's doing!


If replacing the Bearing Box #30207 and #31307 bearings....., a new rolling torque value is critical.
This is a string line/scale rolling torque value, not inch pounds unless correctly converted.
(Some get this wrong! Use Caution! )


As for the 350 horse power/torque....., the 280 transmission should not be an issue.
If concerned, use one of the "A" transmissions (275A, SP-A, DP-A, etc.), as the gear case is heavier.
Definitely replace the Bearing Box bearings if these are questionable.


NOTE: your 280 lower unit (if single prop) incorporates a "slinger" pump.
Oil from the lower is pumped to the upper for cooling, and gravity drains back to the lower unit.
This means that any debris generated from a lower unit issue, is pumped up to, and will contaminate, the upper gears/bearings.
Point being.... do not limit yourself to transmission work only, and examine your lower unit as well!

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Thank you for sharing your expertise.

The outdrive has been apart before due to all the silcone. The drive now is completely apart, upper, intermediate and lower.

I trust my mechanic. Having said that your input is the catylist that gives me confidence.

Well, don't be afraid to ask questions here.
The AQ series is all that I work on these days, so if I can be of any help, fire away... even if it's just to ask about an approximate time frame for a certain procedure!

I just posted to threads whereby shops have estimated $xyz to shim a lower unit to an Intermediate housing.
Cost was in the hundreds of dollars for this work!
This shimming process (minus R&R of oil and the lower unit) takes me about 25-30 minutes to complete, and with accuracy!
Add the time necessary to install the lower, tighten the fasteners, add oil, and that's about another 45 minutes or so.
The question now becomes: Do you enjoy making a large portion of someone else's mortgage payment?

I also hear of so called V/P mechanics getting the AQ series shimming procedure wrong, eventually costing the owner a failure.
I've also heard of these same guys swapping lowers/uppers involving ZERO shimming! ...
Once saw a young guy remove a main drive gear and bearing box, and attempted to install it in an entirely different transmission! ...

It's all right there in the OEM service manual, but for some reason these guys are having trouble with it.

Ask question of these guys before you turn your expensive parts over to them!
If they can't answer the questions.... move on!


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