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Volvo 280 outdrive slips or pops out of gear under load

fbfrmkd

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I have a AQ280 that appears to pop out of gear, possibly even into reverse for a moment at higher rpm (3000 +). It has been sitting 15 years, I did new Bellows and Intermediate shaft bearings recently, and have new sae30 non detergent oil in the drive. (Engine was out to replace the brgs) There are shims between the upper gear unit, and also below the top cap of the upper gear unit, but I did not measure the clearances. this is a twin drive set up. The shift linkage appears solid. Thanks for any information on this. Engine is a Aq240 (Ford 352) with separate controls for throttle and shift. The prop hub appears to be good also.
 
The design and nature of the cone clutch engagement (sliding sleeve/grear cup) should not allow for disengagement while under power. This is, or should be, a very rare occurance.... and should be non-existant when the correct gear oil is used and maintained.
I'd recommend that the transmission be disassembled and that all parts be inspected.

Are you using a LH prop, and have you inspected the vertical shaft brass split ring keeper (aka wear washer)?
Have you have any water intrusion issues with this drive?
 
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I purchased it recently, so I do not know it's history. (other than sitting for the last 15 years) I changed the oil, and the oil that came out was clean. (no water). The upper unit brgs looked good while I had the upper gear box out. The u-joint was not replaced, but felt smooth. Both PDS brgs were replaced while the engine was out. I am using Valvoline SAE 30 Non-Detergent oil in the out-drive. Original removal of the upper unit was very difficult, as the drive shaft was seized onto the drive plate (Flywheel converter plate) I was not aware of the shimming until I was re-assembling the upper unit. I do not think any shims fell out, but may be possible that the shim under the upper unit, and the shim under the top cover could have been swapped? A local boat mechanic told me to make sure it was shimmed properly, but I am unable to locate any specs for this in my Seloc Manual. Could the drive line slip? or likely it it internal to the outdrive, shifting into neutral? (or reverse once, as it killed the engine when this happened?) Thanks for your expert opinions.
 
Ok, while the correct shimming is important and even critical, it is likely not a part of your issue.
It is, however, something that you may want to verify.

Nut-Shelling this, the shimming for this area is to pre-load the bearings (upper/lower driven gear bearings) as to prevent either outer race from spinning within the gear case!
The goal is an approximate .003" squeeze on the bearing, yet allowing the case to close the gap as close to ZERO as possible.
I'd forget the Seloc manual and the codes that are offered via OEM procedure. If the gears have been previously re-set, these codes are no longer usable.
This can be achieved by randomly "over-shimming"......, re-assembling without O-rings and just lightly and evenly tightened into position!
We then take an accurate feeler gauge reading between the two!
Then we reduce the shim pack accordingly, as to net this .003" squeeze on the bearing!
(you will need some additional random thickness OEM shims)
It's actually very easy to do, and it changes nothing to the gear pattern!

Running a RH prop places a "down-load" on the transmission's vertical shaft. This places the load on the top nut of this shaft (not the split ring), so this would eliminate an issue with the brass split ring washer/keeper.
Conversely, a LH prop places an "up-load" on the vertical shaft...... hence the split ring washer regarding wear!

You'd have to pull a transmission apart to see how the sliding sleeve and gear cup engage with one another. But "nut-shelling" this for you, once the friction between the sliding sleeve and gear cup begins, the self perpetuating force (from the steep spiral splines of the vertical shaft) further pulls the two together.
It would be unusual and unlikely that a sliding sleeve and gear cup were to let go once the thrust is applied.... but I'd have to say that this does occur, but rarely!
I have replaced a sliding sleeve in the past, that apparently corrected a similar issue.

The Borg Warner drive coupler and the actual gears are certainly not letting go momentarily.

Honestly, and without seeing this for myself, I'm somewhat stumped!

Have you considered trying a different "like" propeller as to eliminate prop slip, cavitation, spun hub, etc?
 
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Thanks for the feedback Rick, I will examine the prop hub closely, and switch props to eliminate or confirm this as a possibility. I was so concerned with doing additional damage while I was on the water, I may not have looked at all possibility's. It will be a few weeks before I can do another lake test. I will flush the oil also looking for any signs of metal or brass wear. From what you are saying, removing the upper unit to examine (without disassemble) will not provide much, if any value. The coupler for the upper unit, to intermediate unit is fixed once the upper unit is installed I believe. Is there any possibility this could be slipping? (metal sleeve I believe) and not the brass shift sleeve that is part of the upper gear assembly. I do have a complete spare out-drive also that I can swap parts with. (Condition unknown also)
 
what am I looking for as I inspect the vertical shaft brass split ring keeper (aka wear washer)? Is this visible by removing the top cap?
 
The drive coupler attaches to the engine flywheel.
The PDS (primary drive shaft) is the short shaft that joins the drive coupler to the transmission's "universal shaft" female yoke.

The vertical spline coupler is the sleeve that you mention. They will either work, or NOT work.

The vertical shaft brass split ring keeper (aka wear washer) will expand when worn. You can see this when the sides are no longer parallel to one another.

.
 
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Is it possible that sitting for so long with unknown lube in it caused a film to coat the mating surfaces of the clutch and prevent proper lockup?
Also... is the shift cable jacket locked properly to the drive housing? Maybe movement of the cable is causing this the thing to "shift".. the report of going into reverse is what has me wondering about this (unlikely, but checking it is easy)
 
Bob, that is a good point! When/If these become glazed, they may let go. Hard to say for sure.
You'd think though....., that once enough friction caused initial loc-up, it would remain locked!
Hmmm. Ya got me!

I highly doubt that a shift shoe is going to disengage a sleeve/cup while under heavy load.
 
Thank Bill. I have reviewed this thread, but the thread does not indicate the final resolution. Was it a spun prop? Or which proposed solution fixed this. I will be pulling the prop, and re-checking / changing the oil today, and hope to get it back on the water for a test before the snow falls. Again, thanks for all the feedback and suggestion of items to check.
 
This is a quote from my original thread. Since doing this repair I have done over 70 miles most of it on the plane at 20 knots, 3600rpm. I have had NO further issues with jumping out of gear. Before I made these adjustments she was impossible to get on the plane because anything over about 2800 rpm and it would always jump out and the revs would skyrocket.


Quote:-
When forward was engaged, the fulcrum was hitting the base of the drive and I believe not allowing FULL engagement. Vibration over 3000 rpm coupled with the sloppiness in the linkages was allowing the drive to kick itself out of gear - hence the need to throttle back in order to re-engage. I have re-adjusted the linkages to stop the fulcrum hitting and adjusted the cable etc with regard to 'overtravel' as advised by Rick. Hey Presto! No more problems, she happily goes up to 4000 rpm and up on the plane AND stays in gear.

Best of luck, it took me months to find and fix mine - very frustrating
Bill
 
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